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Academy of Surgical Research
Certification Study Guide
2
 Part 1: Introduction
The purpose of this study guide is to create an overview of the information in the
recommended references for the three certification exams administered by the
Academy of Surgical Research. It must be understood that it is these references and
not this study guide that are the ultimate source of exam questions and thus topics
covered in the references may appear on an exam without being covered in this study
guide. However, the majority of the information in the references that might appear
on the exams is outlined here. The outline format is designed to allow applicants to
use the study guide as a note-taking framework when reading the recommended
references.
In any work of this size and scope errors have certainly crept into the text. It is
hoped that the users of the study guide will make the Academy aware of any mistakes
or errors in to allow future corrections. In addition, the purpose of the document is to
assist applicants in studying for their exam. Suggestions and requests are welcome in
order to make this study guide the most useful reference possible for the applicants.
 Part 2: Anesthesia
 Section 2.1: Anesthesia History
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Prior to 1540: Anesthesia was accomplished with the use of opiates, alcohol,
asphyxia, carotid artery compression, physical trauma, and physical restraint
when the above didn’t work or weren’t available
1540: Paracelsus makes ether and notes its effects on fowl
 Overlooked and ignored for the next 300 years
1800: Sir David discovers properties of nitrous oxide
1824: H. H. Hickman demonstrates pain alleviation in dogs using a mixture of
nitrous oxide and carbon dioxide
1831: Liebig discovers chloroform
1842: Ether first used for human anesthesia
1844: Dr. Horace Wells discovers the anesthetic properties of nitrous oxide
 Ignored until 1862
1847: Chloroform used for human anesthesia by Dr. J. Simpson
1847: Chloroform used for animal surgical anesthesia by Flourens
1853: Dr. C. P. Jackson reports extensive use of ether in animal surgery
1854: Dr. G. Dadd advocates humane treatment of animals and application of
scientific principles like anesthesia in animals
 Routinely uses general anesthesia on his surgical patients
1878: Humbert uses IV Chloral Hydrate in the horse
1884: Kohler uses cocaine for local anesthesia in the eye
1898: August Bier produces true spinal anesthesia with cocaine in a dog, himself,
and his assistant
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1900 to late 1920: Ether and chloroform commonly used in small domestic
animals
Late 1920’s: General anesthesia becomes more accepted as the barbiturates are
introduced
1930: Pentobarbital introduced as a general anesthetic
1934: Thiopental introduced
1950: General anesthesia comes into widespread use in large animal surgery due
to the introduction of phenothiazine derivatives as preanesthetics
 This reduces the prolonged and dangerous recovery common
without their use
1964: European Association Of Veterinary Anaesthetists formed
1970: American College of Veterinary Anesthesiology organized
1975: American College of Veterinary Anesthesiologists formed
1995: European College of Veterinary Anaesthesia inaugurated
 Section 2.2: Anesthesia Definitions
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Anesthesia: Derived from the Greek “anaisthaesia” meaning insensibility, it
describes the loss of sensation to the entire or part of the body
Local Anesthesia: Loss of sensation in a defined body area
Regional Anesthesia: Loss of sensation to a larger though limited body area than
described with local anesthesia
General Anesthesia: Drug induced unconsciousness that is characterized by
controlled reversible depression of the CNS and analgesia
Balanced Anesthesia: Induced by a multiple drug approach in which drugs are
targeted to specifically attenuate individual components of the anesthetic state
(consciousness, analgesia, muscle relaxation, and autonomic reflexes)
Dissociative Anesthesia: Induced by drugs that dissociate the thalamocortic and
limbic systems and which is characterized by a cataleptoid state in which the eyes
remain open and swallowing reflexes remain functional
Skeletal muscle hypertonus persists unless a sedative or muscle relaxant has been
given
Surgical Anesthesia: The stage/plane of general anesthesia that provides
unconsciousness, muscular relaxation, and analgesia sufficient for painless
surgery
The actual depth to achieve these conditions may vary with the invasiveness and
painfulness of the procedure
Tranquilization: A state of behavioral change, wherein anxiety is relieved and the
patient is relaxed, although aware of its surroundings
Sedation: State characterized by central depression accompanied by drowsiness
where the patient is unaware of its surroundings
Narcosis: Druginduced state of deep sleep from which the patient cannot be easily
aroused
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Hypnosis: Condition of artificially induced sleep, or a trance resembling sleep,
resulting from moderate depression of the CNS from which the patient is readily
aroused
Anesthesia Types:
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Inhalation: Anesthetic gasses or vapors are inhaled in combination with
oxygen
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Injectable: Anesthetic agents are administered IV, IM, SC, IP, and IT
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Oral and Rectal: Anesthetic agents are administered into the openings of
the GI tract
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Local and Conduction: Anesthetic agents are topically or locally injected
into or around a surgical site or a large nerve trunk supplying a specific
region
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Electronarcosis: Passing an electric current through the cerebrum to
induce deep narcosis
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Transcutaneous Electric nerve stimulation: (TENS, TNS, TES) Local
analgesia is induced with lowintensity, highfrequency electric stimulation
of the skin via surface electrodes
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Acupuncture: An ancient Chinese system of analgesia using fine needles
at predetermined locations
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Hypothermia: Local or general body temperature is lowered to supplement
anesthesia and decrease analgesic drug administration in neonate and
cardiovascular procedures
 Section 2.3: Anesthesia General Issues
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Anesthesia is a reversible process
Anesthetic doses are based on the “average” animal
There is no true “average” animal
The anesthetist must modify the regimen based on experience and the individual
animal’s responses
Response to anesthetic agents relies on metabolism, uptake and distribution
(pharmacokinetics) of the anesthetic, and preexisting disease or pathology
General anesthesia results from interaction of the drug and the CNS
General anesthetics may be divided into two categories:
Injectable
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Enters the blood stream for transport to target tissues
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Requires redistribution
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Generally are detoxified in the liver and excreted via the kidneys
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Metabolism based on firstorder kinetics
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Constant fraction metabolized in a given period
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Gives less control of the elimination process
Inhalation
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Enters the blood stream from the lungs
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Primarily eliminated via the lungs
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Depends on relevant partial pressures and pressure gradients for intake and
elimination
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Gives more control over the anesthetic process due to faster reactions to
changes in administration
The Perfect Anesthetic Agent:
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Does not depend on metabolism for its termination of action and
elimination
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Permits rapid induction, quick depth alteration, and rapid recovery
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Does not depress cardiopulmonary function
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Is not a tissue irritant
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Is inexpensive, stable, noninflammable, and nonexplosive
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Requires no special equipment
Unfortunately, no agent fills all of these roles
Anesthetists must be familiar with methods of action, dangers, equipment
required of the various agents as well as the condition of the animal, desired
experimental outcome, and effects of the surgical procedure to determine which
agent is the best choice for the procedure
Minimum Alveolar Concentration (MAC):
MAC is the amount of inhaled anesthetic required to keep 50% of dogs from
gross movement in reaction to a painful stimulus at 1 atmosphere
Used to test physiological reactions to various stimulus and compounds on
susceptibility to anesthetic agents
Metabolism:
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Small animals have a higher basal metabolic rate (BMR) per unit of
surface area than larger animals
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Thus, small animals require larger doses of anesthetic and analgesic agents
per kg of bodyweight
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Basal metabolic rate increases with activity
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More active animals or during time periods of higher activity require
higher levels of the anesthetic agent(s)
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Disease or pathology may lower metabolic rates
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Adult and geriatric animals have lower BMRs than adolescent and young
adulthood
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Newborns also have lower BMRs than adolescents and young adults
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BMR of male is ~7% higher than an equivalent female
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Fatter animals have slower basal metabolic rates and generally require less
anesthetic
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However, care should be taken as anesthetic agent absorption in adipose
tissue may result in less anesthetic agent freely available in the
bloodstream
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May require more anesthetic early on due to absorption into adipose tissue
but this may result in longer recovery times due to prolonged discharge of
anesthetic agents back into the bloodstream from fat
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This can occur even after anesthetic agents are no longer being
administered as anesthetic agents are still being released into the
bloodstream
 Section 2.4: Stages of General Anesthesia
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Physiological effects of anesthesia are separated into 4 stages:
Stage 1:
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Stage of voluntary movement
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Lasts from initial anesthetic administration to the loss of consciousness
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Tachycardia and hypertension may be present
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Irregular or increased respirations
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Patient may hold breath
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Pupils dilate
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Struggling may be present as animal becomes ataxic
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Some analgesic effects may be present at the transition from stage 1 to
stage 2
Stage 2:
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Stage of delirium or involuntary movement
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CNS becomes depressed
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Loss of voluntary control
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Reflexes become more primitive and exaggerated
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Struggling, breath holding, tachypnea, hyperventilation
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Cardiac arrythmias may occur
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Eyelash and palpebral reflexes are present
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Vocalization
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Salivation
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Susceptible to laryngeal spasm
Stage 3:
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Stage of surgical anesthesia
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Pulse rate returns to normal values
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Muscles relax
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Swallowing and vomiting reflexes are lost
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Divided into 3 or 4 planes depending on the reference
 Three planes: Light, medium, deep
 Four planes: I-IV
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Plane I/Light
 Eyeball movement ceases
 Blood pressure returns to normal
 Strong pulse
 Begins decrease of respiratory rate and depth
 Pupils become less dilated
 Eyeball may rotate
 Eyelash and palpebral reflex present
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 Slight reaction to surgical manipulation
 Loses jaw tone
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Plane II/Medium
 Surgical anesthesia
 Bradycardia begins
 Hypotension increases
 Capillary refill time begins to slow
 Palpebral reflex diminishes and disappears
 Eyeball rotates ventrally
 Abdominal muscle tone finally lost
 Jaw tone minimal
 Pedal reflex absent
 Dysrhythmia possibility at lowest likelihood
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Plane III/Medium
 Deep surgical anesthesia
 Intercostal and abdominal muscle tone minimal
 Weak corneal reflexes
 Diaphragmatic breathing present
 Profound muscle relaxation present
 Centered and dilated pupil
 Bradycardia intensifies
 Hypotension continues to increase
 Respiratory rate and depth continue to decrease
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Plane IV/Deep (Overdose)
 Dysrhythmia probability begins to increase
 Respirations slow and irregular
 Lowered heart rate
 Cyanosis seen
 Widely dilated pupil and unresponsive to light
 Flaccid muscle tone
 Jaw tone lost
 Sphincter control lost
Stage 4:
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Beginning to die
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CNS extremely depressed
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Respirations slow and cease
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Heart begins to cease beating
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Blood pressure at shock level
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Capillary refill time is greatly increased
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Pupils relax
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Dysrhythmia probability at furthest level
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All reflexes and tone lost
 Section 2.5: Anesthesia Pharmacokinetics
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Anesthetic action revolves around plasma concentrations of the anesthetic agent
Blood plasma is the carrier of all anesthetic agents to the CNS not administered
directly into the CSF
Different body parts have different blood supplies and tissue-blood partition
coefficients
This determines which tissues are easier for the drug to enter and leave
Drugs may bind to plasma protein or be distributed in poorly vascularized tissue
and reduce the action of the drug
After introduction to the blood stream, the drug enters various tissues based on
perfusion, capacity for the drug, and the partial pressure gradients
Concentration of drug in blood and tissues is generally a factor of partial pressure
gradients
Partial Pressure Gradients:
Molecules are always in motion, moving in random directions
This random motion will move molecules from areas of high concentrations into
areas of lower concentrations
This is not active, simply there are more molecules to randomly move into the
lower concentration areas than there are to move back out
Eventually, the system reaches equilibrium
This is where both sides have an equal number of molecules with both sides
having some moving to the other in equal amounts
Permeability between the two “sides” will change the number of molecules on
either side at equilibrium
IV Anesthesia:
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IV anesthetic plasma concentration falls rapidly
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Allows quick onset of anesthesia
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Anesthetic effects are rapid and of short duration because the drug is
redistributed into muscle, fat, and vessel poor tissues when drug is rapidly
transferred back to the blood from the CNS
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Duration of action is shorter than with other injectable routes but the drug
is present in the body for longer periods than with inhalants
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Other injectable routes have similar actions once they enter the blood
stream
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The longer time required for IM, SC, IP, etc. administered drugs to enter the
bloodstream allows for a more gradual and longer lasting flow of drug into the
CNS
Allows longer duration of action while taking longer to have effect
Doses are typically higher than with IV administration due to the longer time and
slower influx of the drug into the blood stream
Some anesthetic is already redistributed/metabolized while the drug is still
penetrating into the blood stream from the injection site
Inhalants are volatile chemicals
Molecules are smaller in size than injectable agents
Permeate blood stream, tissues, and blood-brain barrier more quickly
Primarily exhaled rather than biotransformed
Blood-brain barrier:
Permeability characteristics similar to cellular membranes
Limits penetration of nonlipophillic, ionized, or proteinbound drugs
Dependant on partition coefficients, ionization, and protein binding
Affected by hypocarbia and hypercarbia
 Section 2.6: Miscellaneous Anesthesia Issues
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Patient Examination and Evaluation:
Physical Status: Patient’s medical condition (presence or absence of disease) and
the overall efficiency and function of organ systems
Used to determine what drugs should be administered and approximate dosages
Effects on drug uptake, action, elimination, and safety
Nervous, cardiopulmonary, hepatic, and renal are the most important
Examine patient history
Physical exam
Attitude, physical condition, conformation, and temperament
Palpation, percussion, and auscultation
Laboratory exams
Blood panels (BUN, Coagulation, etc.)
Urine
Reference ranges are approximate values
With 10 parameter test there is a 40% chance that 1 value will be out of range on
a normal animal
Use experience for determination
Fasting
Generally for 12 hours
Not advised in small mammals, birds, and neonates which may become
hypoglycemic
Not recommended in ruminants and horses due to possible rumen shutdown
However, distension impairs ventilation and may lead to rupture in the horse
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12-24 hours of water withholding may reduce this chance
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Feeding may lead to increased metabolism as well as possibility of regurgitation
Fluids
Surgical anesthesia and procedures may lead to dehydration
Fluid in body necessary for cell metabolism, intra and extracellular transport, and
life itself
May be administered IV, SC, orally, or IO (intraosseous)
IV fluids should be warmed (~37 degrees C) to prevent hypothermia
IO used for severely dehydrated or traumatized patients with poor or inaccessible
veins/arteries that need rapid fluid absorption into the blood
Common maintenance rate for LRS/Isotonic saline are 10-20 mL/kg/hr
20-30 mL/kg/hr should be used for procedures that involve opening a major body
cavity due to dehydration while the organs are exposed
Lactated Ringers Solution
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Closely approximates electrolyte concentrations of extracellular fluid
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Is isotonic so that it does not induce fluid shifts
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Since it is isotonic it will not replace lost fluid on a 1:1 basis, will
“replace” blood on a 3:1 basis
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Other solutions such as TisUSol are closer to elctrolytic normals
Isotonic (0.9%) and hypotonic (0.45%) saline
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Do not meet free water and electrolyte needs
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May lead to dilution of extracellular electrolytes and buffers with
excessive use
Hypotonic saline with dextrose (2.5%) will act as an isotonic solution
Hypertonic (35%) saline
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Promotes rapid sodium replenishment (hyponatremia)
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Useful in management of shock (esp. hemorrhagic)
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46 mL/kg 7.5%
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Should be given IV
Dextrose (2.550%) solutions
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Provide source of free water for dehydration treatment
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Not effective as plasma expanders
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May be used as a caloric supplement
Sodium bicarbonate
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Treats metabolic acidosis
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Produces sodium retention
 Airway Maintenance:
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For successful anesthesia, an open airway is essential
If the airway is blocked, the animal dies
If the airway is partially occluded this may cause a decrease in available oxygen
to the lungs
This may lead to stress and strain to the animal as the body attempts
compensation for the lack of enough oxygen
Animal positioning is the easiest method to maintain a patent airway
Place the animal’s head and torso in a normal anatomical position
Positioning alone may not be adequate if:
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The head must be placed in a poor anatomical position to provide surgical
access
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Procedure’s positioning/restraint does not allow easy access or
repositioning (i.e., stereotaxic apparatus)
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Animal has significant oral/respiratory secretions or potential for
stomach/rumen regurgitation
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In addition, delivery of oxygen or inhalant agents may require use of a
face mask or endotracheal tube
Face mask
Good low tech method to deliver gas to the animal’s respiratory system and not to
the general room
–Not perfect as the seal is not gastight and there will be some leakage into the
room
Leakage of inhalant anesthetic agents may be dangerous
Endotracheal Tubes
Maintain a patent airway
Protect airway from foreign material
Allow use of positive pressure ventilation
Effective delivery of oxygen, inhalant anesthetic agents, and directed test
compounds
Suction of trachea or bronchi
May be made of polyvinyl chloride, silicone, plastic, or rubber
Red rubber not advised for use due to a propensity for cracking, difficulty in
cleaning, and opacity
Cole Endotracheal tubes
Uncuffed
Have a “shoulder” that leads to a thinner tip
Shoulder “seals” against the arytenoid cartilages
Should not contact the larynx to avoid pressure on laryngeal cartilages which can
cause laryngeal dilation
Choice of a proper end diameter (laryngotracheal portion of tube) should create a
seal
Murphy Endotracheal tubes
Cuffed
Allows a better seal and does not require precise tip/shoulder placement
Overinflation can rupture the cuff or cause pressure trauma to the airway
(ischemic injury, mucosal damage, and ultimately tracheal strictures)
Recommended pressure of air in cuff 1025 mm Hg
May be reinforced or armored with wire/plastic to prevent kinking
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Will have smaller interior lumens, which can increase resistance to airflow
May be reinforced/colored to prevent breaching by laser light during oral
procedures
 Intubation:
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Basic technique:
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Induce anesthesia
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Place animal in an appropriate position, normally sternal recumbency
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Dorsal recumbency may be useful for swine and primates
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Open the animal’s mouth
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Pull the tongue forward and out
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Apply topical lidocaine spray or liquid to the larynx to prevent
laryngospasm (Optional)
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Alternatively, apply lidocaine jelly to the tip of the endotracheal tube
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Visualize the epiglottis and glottis
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A laryngoscope may be helpful
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Introduce the endotracheal tube into the trachea and advance until the tip
is at the approximate level of the thoracic inlet
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An internal stylet to stiffen the tube may be useful
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Gauging the appropriate distance to advance the tube in the trachea prior
to intubation is quite helpful
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Secure the tube in place with tape or gauze
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Gauze may slip in animals with excessive salivation such as ruminants
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Inflate the cuff if applicable
Laryngoscopes
Useful for visualizing the glottis and allowing easier intubation
It is preferable to use a laryngoscope for better visualization than to show off
how practiced one is while injuring the animal because one can’t see
Care should be taken not to irritate the epiglottis with the laryngoscope blade
Holding the epiglottis with the blade may be traumatic
Two main styles of blade
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Miller: straight
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Bizarri-Guiffrida: curved
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Alternate Methods of intubation:
Place a thin guide catheter like a urinary catheter into the trachea, thread an
endotracheal tube over it into the trachea, and remove the guide catheter
After surgically prepping the skin over the trachea, insert a Venicathstyle needle
and catheter through the skin and into the trachea, advance the Venicath into the
trachea until it is visible in the mouth, thread an endotracheal tube over the
Venicath into the trachea, remove the Venicath, and finish placing the
endotracheal tube
Species specific concerns:
Horses, cows, sheep, and goats
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Usually are eating prior to induction, may require flushing debris from the
mouth to allow visualization and to not carry debris into the bronchi
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Lubrication of the tube with watersoluble lubricants is helpful

Visualization may be difficult due to the distance from the mouth to the
epiglottis
Cats
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Difficult visualization
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Pressure under the neck will shift the soft palate and obscure the view

Inadequately anesthetized animals may bite down on fingers within the
mouth
Rabbits
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Present a very small glottis with poor visualization from the mouth
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Extending the head back is helpful during blind intubation
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Carefully observe condensation or listen for breath sounds while slowly
advancing tube to allow adequate feedback

Following a guide cannula may be useful
Rodents
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Small size makes visualization difficult

Using a guide catheter or retrograde guide tube may help
Swine

Intubation is potentially dangerous due to the false pockets which are
highly vascularized pouches outside the trachea
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If irritated they may bleed profusely

Prone to laryngospasm
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Tube may bind due to sharp angle of route from the mouth into the trachea

Gently twisting the tube while advancing is beneficial

Lubrication of the endotracheal tube is important

As an alternate method for intubation of swine, place pig in dorsal
recumbency to which may straighten the pathway for the endotracheal
tube
Ruminants will regurgitate rumen fluid and saliva

Lower head below chest level and/or place a rumen tube and collection
bag

Rumen tube will also prevent rumen gas distension
Thermoregulation:
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Heating blankets (electric, waterrecirculating, warm air) and/or heated tables
should be used to maintain body temperature during surgery
Most anesthetic agents depress the thermoregulatory centers and metabolism
which leads to accelerated body heat loss
 Recovery:
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Small animals
Place in lateral recumbency
Flip from side to side every 1015 minutes to prevent the lower lung from
noninflation, atelectasis, and fluid accumulation
Remove endotracheal tube when swallowing reflex returns
If animal is not intubated, pull tongue forward to preclude blocking the pharynx
Remove water pans until animal is conscious
Do not place recovering animals with conscious animals as conscious animals
may harm unconscious animals
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Especially with pigs and rats
Large animals (livestock)
Remove animal to a padded room/stall
Special care should be taken with horses and cows as they can severely harm
themselves while struggling during recovery
Oxygen and suction should be readily available
Ruminants should be maintained in sternal recumbency and have their head held
higher than their chest to prevent regurgitation and aspiration of rumen contents
Alternatively, with endotracheal tube present and cuff inflated, extend head
forward and down
 Section 2.7: Anesthetic Issues with Disease and
Pathology:
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Cardiovascular dysfunction:
Most preanesthetic and anesthetic agents cause CV depression
Animals with cardiovascular dysfunction are more prone to fluid overload and
arrythmias
They may also have a decreased cardiac reserve
Pulmonary dysfunction:
Most preanesthetic and anesthetic agents cause pulmonary depression
Pulmonary dysfunction may be caused by diaphragmatic hernia, pneumothorax,
hydrothorax, pneumonia, pulmonary edema, atelectasis, obstruction
This condition will require the anesthetist to perform a careful balancing act
between lowering doses, primarily preanesthetic drugs, to limit further
compromise while also preventing anxiety which will compromise the pulmonary
system
Intubation and ventilation are key
Rapid induction of anesthesia following sedation may be required to permit
adequate airflow via intubation
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Positive pressure ventilation best achieved with inhalation anesthetics
Wariness with nitrous oxide is warranted due to its effects on pneumothorax
Neurologic disease:
Usually refers to spinal cord and to a lesser extent intracranial disorders
Intracranial Pressure (ICP) and Cerebral Blood Flow (CBF) are regulated in
conscious animals
Anesthetized animals may lose this regulation, leading to increases in either of
them
ICP and CBF increases in head trauma patients may cause further damage
Increases may lead to respiratory center depression
Most injectable anesthetics lower ICP and CBF
Inhalation anesthetics commonly raise ICP and CBF
Nitrous oxide causes the greatest increases
Renal disease:
All anesthetic agents are likely to decrease the rate of filtration
Stress also lowers the rate of filtration
Effects may terminate at the conclusion of surgery or can linger for days
May reduce elimination of anesthetic agents or even increase plasma
concentrations due to going acidotic
Increases of potassium (K+) which are already present may be elevated in serum
to the point of being lifethreatening
K+ increases may be seen on the ECG in a peaked T wave, prolonged PR interval,
wide QRS complexes, and loss of P wave
Chronic renal failure may lead to anemia
Rupture of urinary bladder
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Animal may become hyperkalemic, hyponatremic, hypochloremic, and
acidotic
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An emergency, lifethreatening situation
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Serum K+ increases
Hepatic disease
Injectable preanesthetics and anesthetics may cause problems, especially
acepromazine, thiobarbituates, and the alpha2adrenergic agents
Propofol, ketamine, and inhalation anesthetics are generally the safest
The elimination rate of drugs may be lowered due to reduced liver function
May result in reduced coagulation abilities
Gastrointestinal disease:
Damaged GI tract may release toxins into the blood stream
May decrease cardiac function and ventilation (distended stomach)
Endocrine disorders
May be a result of diabetes mellitus or Addison’s disease
Anesthetic regimen is not as important as proper treatment of the condition itself
Preanesthetic and anesthetic agents should be selected for the shortest recovery
time or easiest reversibility
16
 Section 2.8: Preanesthetic Agents and Adjuncts
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Reasons for use:
Calm the patient
Induce sedation
Provide analgesia and muscle relaxation
Decrease airway secretion and salivation
Obtund autonomic reflex responses
Decrease gastric fluid volume and acidity
Suppress or prevent vomiting
Decrease anesthetic requirements
Promote smooth induction and recovery from anesthesia
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Anticholinergics
Tranquilizers
Opioids
Alpha2adrenergic agonists
Alpha2adrenergic antagonists
Tranquilizeropioid combinations
Paralytic agents
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Block certain acetylcholine (neurotransmitter) receptors
Reduce secretions (saliva) (antisialogogic activity)
Prevent vagal inhibition (bradycardia) and GI stimulation (inhibits intestinal
peristalsis)
Reduce vagus nerve response (vomiting and laryngospasm)
Relieve cholinergicmediated bronchoconstriction and promotes bronchodilation
Dilate the pupil and reduce tear secretions
Diminish the effect of acetylcholine
Treatment of choice for opioid, xylazine, and vagal reflex activity induced
bradycardia
Atropine Sulfate
Decrease oral, respiratory, and pharyngeal secretions
Increase anatomic and physiologic respiratory dead space
Suppresse vagal influence on the heart
Decrease lacrimation
Increase incidence of cardiac dysrhythmias and sinus tachycardia in dogs
Contraindicated with tachycardia, constipation, and obstruction
May cause thick mucus secretions in cats
Cats, rats, and rabbits (3360%) may have atropine esterase

Will destroy large amounts of atropine and limit effectiveness
Overdose may cause dry mucous membranes, thirst, dilated pupils, and
tachycardia
 Types of Preanesthetic and Anesthetic Adjuncts:
 Anticholinergics:
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Dogs more susceptible
Can be treated with repeated doses (if needed) of 0.02 mg/kg physostigmine to a
maximum of 0.5 mg/animal administered IV over several minutes
Repeated doses should be stopped at a total dose of 2 mg/animal
Minimally effective in sheep and goats
Will prolong thiopental anesthesia and even cause reanesthetization in dogs
Not recommended in rodents due to their rapid HR
Not recommended in ruminants due to increased saliva viscosity, short duration,
and the increased incidence of bloat
Glycopyrrolate
Synthetic quaternary ammonium
Decrease volume and acidity of gastric secretions, intestinal motility, and
tracheal, bronchial, and pharyngeal secretions
Reduce diffusion over bloodbrain or placental membranes
Block vagal reflexes
Lasts longer than atropine sulfate
Prevents ketamine/xylazine associated bradycardia in rabbits
Lasts longer than atropine but has a longer onset of action in ruminants
 Tranquilizers:
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Relieve anxiety
Quiet and calm the animal
Decrease anesthetic dosages
Reduce vomiting
Have no analgesic effects
Anesthesia recovery is smoother
Reduce histamine release (allergy)
Promote skeletal muscle relaxation (benzodiazepine agents)
May promote vasodilation (phenothiazine agents)
Leads to drop in BP (hypotension) and excessive heat loss
May lower seizure thresholds (phenothiazine agents)
Act as anticonvulsants (benzodiazepine agents)
Benzodiazepine agents have minimal side affects
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Clinical effects
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Hanging head
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Drooping ears
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Glazed eyes
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Protruding nictitating membranes
Acepromazine maleate
Phenothiazine derivative
Potent neuroleptic agent with low toxicity
Dogs; dose should not exceed 3 mg
May reduce or prevent malignant hyperthermia in swine
Droperidol
Butyrophenone tranquilizer
18
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Alphaadrenergic antagonist
May prevent epinephrineinduced dysrhythmias
Decreases barbiturate doses
Primarily used as a component of InnovarVet in a mixture with fentanyl
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Extremely effective combination
Diazepam (Valium)
Benzodiazepine
Prevents seizures
Rapidly passes bloodbrain and placental barriers
Should be injected slowly to prevent venous thrombosis and must not be injected
in an artery
Not recommended for intramuscular admin (painful)
High doses cause slight decrease in respiration, BP, and CO and increase HR
Relatively low toxicity
Shouldn’t be mixed with other agents (precipitation)
Cats and dogs does not induce sedation alone
Midazolam
Benzodiazepine
Shorter duration of action and clearance than diazepam
May cause behavioral changes in dogs and cats
Pacing, vocalization
Nonirritating and suitable for IM injection
Can be mixed with other preanesthetic agents
Flumazenil
Reverses CNS action of benzodiazepines
 Rapid action 24 minutes
Reversal is not accompanied by anxiety, tachycardia, or hypertension
Replaced aminophylline and physostigmine
 Opioids:
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Analgesics that will depress the CNS and lower the required amount of anesthetic
agents
Will not cause unconsciousness at therapeutic doses
Addictive
Most are controlled substances
Require extensive DEA paperwork
Relieve continuous dull pain better than sharp and intermittent pain
Morphine sulfate
Major pharmacologic effect is analgesia
Induces a rapid and marked increase in serotonin synthesis
Depresses medullary respiratory, cough, and vasomotor centers
Does not affect motor function
Decreases BMR and body temp (13o F)
Stimulates the vomiting center
Reflex centers of spinal cord stimulated
19
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Use as a preanesthetic agent is confined almost entirely to dogs
Causes variable effects on the brain in other species (excitement)
Metabolized in the liver and eliminated in urine
Has a dose dependant decrease on bile flow
 Does not appear to affect ruminants
Large doses will provoke “rage” in cats
Poor effects on neuropathic pain
Nerve lesion or disease
Meperidine hydrochloride (Demerol, Pethidine)
Analgesic effect 1/10th that of morphine
Rapidly excreted
Reduces salivary and respiratory secretions
Does not cause vomiting
Rapid IV administration not recommended (may cause hypotension &
convulsions)
SC administration 30 minutes prior to anesthesia
Has “notable” local anesthetic ability
Methadone hydrochloride (Methadone, Dolophine)
Synthetic opioid unrelated to morphine
Reversed with opioid antagonist
Stimulates respiration rate
Analgesia lasts 2 to 6 hours
Decreases barbiturate dose by ~50%
Oxymorphone hydrochloride (Numorphan)
Semisynthetic opioid
10 times more potent than morphine
Little respiratory or cough depression
Decreases barbiturate dose ~3366%
Can be used to provide effective epidural analgesia
Fentanyl Citrate
250 times more potent than morphine
Rapid onset of action
Short duration with peak at 30 minutes
Depresses respiration and may persist for hours
Exaggerates response to loud noises
Causes vagalmediated bradycardia unless countered (atropine)
Little cardiac output or bloode pressure effects
If administered with barbiturates may cause bradycardia, hypotension, and
respiratory depression
Carfentanil citrate
10,000 times more potent than Morphine
May be administered by applying to buccal or nasal mucosa
Used primarily for capture of wild animals
Sufentanil
20
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Thienyl analog of fentanyl
5 to 10 times as potent as fentanyl
Elimination halflife is 2 to 2.5 hours
May induce bradycardia
Provides unpredictable anesthesia, bradycardia, hypoventillation, and poor muscle
relaxation in dogs when used alone
When combined with potent tranquilizers and glycopyrrolate it is an effective
neuroleptanesthesic agent
Alfentanil
1/5th to 1/10th as potent as fentanyl
Has more rapid onset of action than fentanyl or sufentanil
Etorphine hydrochloride
Oripavine derivative
80 to 1000 times more potent than morphine (SC)
Can be antagonized with nalorphine or diprenorphine
Used primarily for the capture of wild animals
Butorphanol tartrate (Torbugesic)
Synthetic opioid
3 to 5 times as potent as morphine
Less respiratory depression than morphine
Reaches a “ceiling” where additional doses have little effect
Excellent analgesic when combined with xylazine or detomidine (cattle and
horses)
Antagonizes sedative effects or morphine and oxymorphine
Buprenorphine (Buprenex)
Partial muopioid agonistantagonist
25 to 30 times as potent as morphine (agonist)
Maximum analgesic effect less than morphine
Onset of action relatively slow (2030 minutes)
Causes respiratory depression
Reversed by naloxone and naltrexone
IM administration lasts 68 hours
Epidural administration lasts 1824 hours
Mostly excreted unchanged in feces (proteinbound)
Pentazocine lactate (Talwin)
1/3rd as effective as morphine (in people)
Minimal CV effects
Mild respiratory depressant
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Mediate sedation and analgesia
Produce sedation, muscle relaxation, and analgesia
Not potent respiratory depressants
Not addictive
Act as anticonvulsants
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 Alpha2Adrenergic Agonists:
21
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Have a widerange of drug interactions
Barbiturate, inhalant, and dissociative anesthetic doses should be lowered when
used in combination with Alpha2Adrenergic Agonists
Xylazine hydrochloride (Rompun)
Acts as a sedative and analgesic
Most common sedativeanalgesic in horses and cattle
Combined with ketamine acts as a shortterm surgical anesthetic agent
May be combined with butorphanol to improve analgesia and sedation
Major effects develop in 10 to 15 minutes (IM) or 3 to 5 minutes (IV)
Duration of analgesia is less than 1 hour
IV bolus causes bradycardia and brief hypotension followed by decrease in CO
(1/3) and BP (1/4 to 1/3)
IM administration has less drastic effects
Has poor efficacy in swine
Has a wide margin of safety
Dose increase prolongs effects but does not generally increase the degree of
sedation
May cause emesis in cats and dogs
Increases urine output in cattle, horses, and cats
Causes mydriasis
Excited animals (stress, fear, pain) may evince lowered xylazine effectiveness
Painful procedures should be limited to 10 to 15 minutes after the onset of
sedation
IV overdose or arterial administration may cause seizures and collapse
Can produce 2nd degree heart block
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Relatively harmless arrhythmia originating at or below the AV node
May show respiratory depression
Has a significant local anesthetic effect
Epidural administration creates more profound and longer lasting effects than
lidocaine
Reduces secretion of insulin in the pancreas
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Not usually harmful except in dehydrated patients where hyperglycemia
can lead to transient osmotic diuresis
Will affect blood glucose levels
Detomidine
Developed for horses and cattle
Similar cardiovascular effects to xylazine
Commonly combined with opioids for enhanced sedation and analgesia
May be used as a preanesthetic or combined with ketamine for anesthesia
Medetomidine
More potent and longer lasting than the other Alpha2Adrenergic Agonists
BP and RR are decreased in a dosedependant manner
Alpha2Adrenergic Antagonists:
Used as reversal agents for injectable anesthetics
22
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Yohimbine
Reverses xylazine, ketamine, and pentobarbital combinations when combined
with 4-aminopyridine
Also shown to work well by itself to reverse xylazine
Tolazoline
Reverses xylazine
Partially reverses some anesthetic drug combinations with xylazine
Atipamezole
Selectivity ratio is 200 to 300 times higher than yohimbine
Rapid IV doses may cause death or severe hypotension and tachycardia
May be prevented by slower administration
Tranquilizer-Opioid Combinations:
Used to provide pronounced sedation and analgesia to allow minor surgical
procedures
Fentanyl citrate Droperidol (Innovarvet) is the primary example
Produces neuroleptanalgesia
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State of sedation with analgesia sufficient for minor surgery
Induces intense analgesic actions with relatively short durations
Produces sedation, analgesia, immobilization, respiratory depression, decrease in
BP, and bradycardia
Provides wide margin of safety and easy recovery
Partially reversed with opioid antagonists
 Paralytic (Muscle Relaxant) Agents:
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Provide superior muscle relaxation as an adjunct to general anesthesia
Allow easier intubation and ventilation, improves cardiovascular anesthetic
management, and provide less muscle resistance in long-bone orthopedics and
abdominal surgery (reduces anesthesia dose required to minimize tension)
DO NOT PROVIDE ANALGESIA OR UNCONSCIOUSNESS
Are expressly prohibited for sole anesthetic use by the Guide
Usually require mechanical ventilation due to paralyzed diaphragm and
intercostals muscles
Create more difficult anesthesia management
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Twitching and respiratory signs for maintenance of anesthesia are
minimized
When paralytics are being used the anesthetist should monitor HR, BP, ECG, and
arterial blood gas to gain information on the animal’s physiologic state
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An inadequately anesthetized animal will show signs of tachycardia,
arrhythmias, hypertension,and acidosis
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Mydriasis and lacrimation may be present
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Horses will sweat
Anesthesiologist may also monitor the response of a peripheral nerve to an
electrical stimulus
23
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Interact with some antibiotics, lithium compounds, local anesthetics, barbiturates,
quinidine, propanolol, calcium antagonists, diuretics, immunosuppressants, and
corticosteroids
Guaifenesin (glyceryl guaiacolate)
Affects tonic (supportive) muscles to the greatest degree
Minimally affects respiratory muscles

Differentiates it from other paralytic agents
Used during induction and short periods of parenteral and inhalation anesthesia
May elevate heart rate
Metabolized by the liver and excreted by kidneys
May be combined with xylazine, ketamine, thiopental, and pentobarbital
Neuromuscular (Blocking) Paralytic Agents
Interact with receptors at the neuromuscular junction
Interfere with transmission of signal from motor neuron to muscle
Divided into depolarizing and polarizing agents
 Depolarizing Neuromuscular Paralytic Agents:
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o
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Depolarizing agents mimic the action of acetylcholine
Not antagonized by acetylcholine
Increased amounts of agents AT THE NEUROMUSCULAR JUNCTION will not
prolong the block
Causes initial depolarization of the end plate but do not depart for minutes to
hours
Keeps the motor neuron from repolarizing and firing again
Succinylcholine
Must be refrigerated
Rapid onset
Provides excellent relaxation
Will cause marked fasciculation (twitching) for approximately 30 minutes before
muscles relax
Large doses, repeat doses, or prolonged administration may create a phase II
block
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Characteristic of nondepolarizing blocks
May not be reversible
Has several undesirable side effects
Initial muscle fasciculation and extensor rigidity may cause muscle pain and
stiffness and microscopic muscle damage
May cause hypertension, tachycardia, sinus bradycardia, cardiac arrhythmias, and
cardiac arrest
Rise in intraocular pressure
Increased blood serum potassium
Action prolonged by pregnancy and hepatic disease
Can be potentiated by inhalation and local anesthetics
Cats, swine, and ponies are resistant
Increases intracranial pressure (cats and dogs) despite thiopental or pentobarbital
anesthesia
24
 Nondepolarizing Neuromuscular Paralytic Agents:
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Compete with acetylcholine for receptors
Do not cause muscle repolarization
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Actually prevent it
 Have a slow onset of action
 Will have prolonged action if hepatic or renal function is impaired
 Large doses or prolonged administration time can result in prolonged effects
 Two divisions:
 Steroid analogs: pancuronium, vecuronium, pipecuronium, and rocuronium
 Benzylisoquinoliniums: curare, tubocurarine, metocurine, gallamine, atracurium,
doxacurium, and mivacurium
 Pancuronium
 Lasts 20 to 30 minutes
 Acts as a comparatively longacting relaxant
 Causes increased HR (vagal blockade)
 Prolonged administration will result in a difficult reversal
 Metabolized in liver
 Metabolites have weaker relaxant properties
 Relies on kidney for elimination
 Vecuronium
 More potent and shorter acting than pancuronium
 Prolonged with renal or hepatic failure
 Does not affect heart rate unless extremely large doses are given
 Relatively fast recovery
 Widely used
 Pipecuronium
 Long acting
 Twice the duration of pancuronium
o 2 to 4 times as potent
 Has a rapid onset of action
 May be retained in the kidneys for days
 Does not affect heart rate at up to 100 times the therapeutic dose
 Rocuronium
 20% as potent as vecuronium
 Less dependant on renal clearance
 Has rapid onset
 Increased doses hasten onset but will also prolong the duration of activity
 Rapid recovery
 Cumulative doses not noted (cats)
 Curare (dTubocurarine)
 Long acting
 Increases heart rate
 Metabolized in the liver and excreted by the kidneys
 Small proportion is excreted in bile
25
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Causes vasodilation, hypotension, and tachycardia
Metocurine
Much improved safety margin over curare
Relies on renal excretion with 2% excreted in bile
Gallamine
Relatively impotent
Long acting
Consistently produces tachycardia
Is the only nondepolarizng relaxant that crosses the placenta
Relies on renal excretion
Atracurium
Must be refrigerated
Unstable molecule and breaks down by itself at body temperature
An intermediate musclerelaxant
Not prolonged by renal and hepatic disorders
Widely used
Doxacurium
Long acting
Has no autonomic side effects
Mivacurium
Lasts slightly longer than succinylcholine and 1/2 the duration of vecuronium
Does not have autonomic effects
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Have little effect if a large dose of these nondepolarizing neuromuscular paralytic
agents has just been administered
Best used when spontaneous recovery of muscle strength has begun
Anticholinerases
Edrophonium, neostigmine, pyridostigmine
May cause bradycardia, bradyarrhythmias, and various secretions
4 Aminopyridine and Guanidine
Causes CNS stimulation (restlessness, confusion, and convulsions)
Best combined with acetylcholinesterases
Calcium
Only partially effective
 Reversal agents:
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 Section 2.9: Injectable Anesthetic Agents and Adjuncts
 Injectable Anesthesia:
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Each agent has relatively specific effects
Generally requires a combination of drugs to affect all necessary bodily systems
adequately
Allows specific physiologic targeting by the choice of anesthetic drugs
Inhalant anesthetics increase or decrease all components of anesthesia at the same
time
26
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Includes side effects
Anesthetic agents in general are variable to the individual
Doses are a guide, not an absolute
Remember, opioids ARE NOT anesthetics
 Barbiturates:
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Contain a pyrimidine nucleus
Divided into 4 groups based on duration of action:
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Ultrashort: Hexobarbital, Kemithal, Thiamylal, Thiopental
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Short: Cyclobarbital, Cyclopal, Pentobarbital, Secobarbital
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Intermediate: Allylbarbituric acid, Amobarbital, Aprobarbital,
Butabarbital, Butallylonal, Hexethal, Probarbital, Propallylonal,
Vinbarbital
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Long: Barbital, Diallylbarbituric acid, Mephobarbital, Phenobarbital
Short and ultrashort duration barbiturates are the barbiturates used for clinical
anesthesia
Intermediate and long duration barbiturates are used for sedation and control of
seizures
Depress the CNS neurons
Barbiturate anesthetics can lead to respiratory depression, central and peripheral
cardiovascular depression, decreased blood pressure, decreased basal metabolic
rate, lowered body temperature, decreased cerebral metabolic rate, reduced
cardiac output, reduced stroke volume, and an increase in heart rate
Are hypnotic sedatives
Cross cell walls and the placenta
Cerebrospinal fluid contains less protein for binding than plasma and hence has
lower barbiturate concentration at equilibrium
Ultrashort acting barbiturates are redistributed faster, NOT metabolized faster,
than the short acting barbiturates
Glucose effect: During recovery glucose administration will lead to
reanesthetization
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Dogs are less susceptible
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Rats and mice are not susceptible
IV administration is the preferred route
IP administration does not allow accurate dosage control to effect
Oral administration is variable and usually used for sedation
Administered “to effect”
First 1/3 of estimated dose is rapidly injected
Slow initial injection may cause excitability
Remainder given slowly to effect
Recommended administration is through a catheter in small animals
Perivascular administration will result in “barbiturate slough”
Takes 2 to 4 weeks to heal and will scar
Lidocaine or 2% procaine (12 mL) may be injected into the area to prevent
vasospasm and change the acidity to help minimize damage
27
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Saline may also be infused to further dilute the barbiturate
Corticosteroids, NSAIDs and/or the use of hot packs may also help
Oxybarbiturates:
Phenobarbital Sodium
Long-acting
Effective anticonvulsant
Excreted slowly in urine
Tends to be cumulative
Pentobarbital Sodium
After single IV dose arterial BP decreases and HR increases for 10 to 20 minutes
Prolonged anesthesia leads to decrease in systolic BP, stroke volume, pulse
pressure, central venous pressure, PaO2, pH, CO, and BT
HR, PaCO2, and peripheral resistance increases after 1.5 hours
Deep anesthesia depresses renal function
Effect produced by high doses may closely resemble those of shock
Freely crosses the placenta
No longer used in North America for cows and horses
May show crying, shivering, running motions, and thrashing during recovery
Advised to use tranquilizers for the recovery period
Methohexital Sodium (Brevital)
Ultrashort acting
Contains no sulfur atom
Duration of action due more to redistribution than metabolism
Main danger of overdose is respiratory failure
Recovery is difficult even with preanesthetic sedation
Best followed by standard inhalant anesthesia
Good drug for induction of anesthesia
Thiobarbiturates :
Thiopental sodium
Produces ~12 different metabolic products
86% excreted in urine within 4 days
Initially creates a marked respiratory depression
Five minutes post-administration: increase in heart rate, aortic pressure, peripheral
vascular resistance, and left ventricular pressure
Arrhythmias are accentuated by xylazine, halothane, methohexital and
epinephrine
Cardiovascular effects are reduced if administered along with a lidocaine bolus
Has ultrashort action due to rapid redistribution and localization in fat
Thiamylal sodium
Normal saline suggested as a diluent
Solutions stable for up to 14 days
Less cumulative than thiopental
Tolerance to repeated injections not noted
More arrhythmogenic than thiopental
28
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Less cardiovascular effects than thiopental
Single bolus provides ~15 minutes of surgical anesthesia
May be used alone or in combination with guaifenesin in horses and cattle
May produce apnea
Very safe and nontoxic
Nonbarbiturate Anesthetic Drugs:
Althesin
Combination of the steroids alphaxalone and alphadolone acetate
Has little cumulative effect
Should not be used along with barbiturates
Does not cause damage with perivascular administration
Produces good muscle relaxation
Additional doses are not cumulative
May cause edema of the feet, ears, and muzzle (cats) or allergic reaction
consisting of a decrease in blood pressure and wheals at the injection site (dog)
Causes violent recovery in horses
Chloral Hydrate, U.S.P.
May be administered orally or IV/IP if placed in solution
Oral admin may cause vomiting
Depresses the cerebrum
Subanesthetic doses do not affect motor and sensory nerves
Is a good hypnotic but poor anesthetic
Amount needed for anesthesia is close to the lethal dose
Lasts for several hours
Has weak analgesic action
Fallen out of use for small animals and livestock
Perivascular administration is irritating
Doses vary extensively
Chloralose
Produced by heating anhydrous glucose and trichloroacetaldehyde in a water bath
to produce alphachloralose
Produces minimal CV depression and better maintains active reflexes
Provides less depression of neuronal function of the cortex than pentobarbital
Valuable for long duration nonsurvival experiments
Urethane, N.F.
Prepared by heating urea with alcohol under pressure
Mutagenic, carcinostatic, and carcinogenic
Fallen out of use
Magnesium sulfate
Globally depresses CNS
May be used for euthanasia but only if administered AFTER the animal is
rendered unconscious with another agent
Metomidate (Hypnodil)
A hypnotic with relaxant properties
29
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Induces sleep without analgesia
Has minimal cumulative effects
Etomidate
Does not depress CV or respiratory centers or cause histamine release
Does not trigger malignant hypothermia in swine
Has anticonvulsant properties
Venous pain during injection is common (humans)
May be a preferred drug for traumatized patients or those with CV or respiratory
difficulties
Propofol
Is not a barbiturate, steroid, or euganol
Will support microbial growth and endotoxin production

Unused drug should be discarded after 12 hours
Rapid uptake into the CNS promotes rapid induction
Rapidly redistributed from the brain and metabolized from blood
Promotes quick and smooth recovery
Has minimal analgesic activity at subanesthetic doses

Animal will respond to painful stimuli even under anesthesia
Acepromazine “onboard” will decrease the amount needed
Decreases intracranial pressure
Repeated doses in cats may cause injury to red blood cells
Relatively expensive
Propanidid
Difficult to administer fast enough to cause anesthesia
An eugenal
Extremely short duration of action
Causes severe respiratory depression and hypotension in dogs
Tricaine Methanesulfonate (MS222)
Used for anesthesia of amphibians and fish by bathing, gill spraying, or injection
May be autoclaved
Useful for fish, sharks, rays, etc.
 Dissociative Anesthetics:
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Used to interrupt ascending transmission from the unconscious to the conscious
parts of the brain rather than generalized brain center depression
Characterized by a cataleptoid state in which the eyes remain open with a slow
nystagmic gaze
Provides intense but short duration analgesia
Ketamine
Most common dissociative injectable
Least potent dissociative
Clinically available ketamine is actually a racemic mixture (composed of two
isomers)
Produces doserelated unconsciousness and analgesia
Bolus IV injection rapidly crosses the bloodbrain barrier
30
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Has a rapid onset of action
Termination of effect due to rapid redistribution
pH is 3.5, so this may lead to some tissue irritation after IM injection
Primary effect at the thalamoneocortical projection system
Does not induce seizures and may be an anticonvulsant
Analgesic effects greater for somatic pain than visceral pain
Increases cerebral blood flow, intracranial pressure, CSF pressure, HR, MAP, and
CO
Causes transient decrease in respiratory rate
Hallucinatory behavior may be evident during recovery
Dogs and horses show extensive hepatic metabolism before elimination
Cats eliminate most unchanged via the kidney
Skeletal muscle tone not affected
Often combined with xylazine, guaifenesin, diazepam, medetomidine, or
morphine (or derivative) to mitigate excitatory effects
Survival rate for “shocky” animals better than with Halothane
Telazol
Has a wide margin of safety
Induction and recovery are rapid and smooth
Swallowing, coughing, pedal, corneal, and vomiting reflexes are retained
Good muscle relaxant
Has lingering analgesic effects
May cause increase in HR and respiratory rate
MAP may decrease transiently and then decrease
May be combined with ketamine and/or xylazine
Mixture of tiletamine hydrochloride and zolazepam
Tiletamine hydrochloride
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More effective than ketamine
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Pharmacodynamics similar to ketamine
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Causes excitability in rats and mice
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Large doses produce analgesia and anesthesia
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May produce transient HR and MAP decreases
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Overdose will cause hypoventilation and apnea and may increase urine
output
Zolazepam
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Does not cause anesthesia or tranquilization in cats
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Has minimal CNS depressive effects
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Used to create a mixture that has limited CNS depressant effects
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Does not cause sufficient muscle relaxation or analgesia in swine when
used alone
 Section 2.10: Physical Methods of Anesthesia
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Hypothermia
31
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Heart, brain, liver, and some other vital organs can survive for longer periods at
low temperatures without a portion or all of their blood supply
May be general or localized
Shivering must be controlled initially by another anesthetic agent
Risks profound CNS and vital organ depression
May cause severe drops in blood pressure
Below 28 degrees Celsius heart muscle may show ventricular fibrillation which
will rapidly deplete cardiac muscle stores
Heart may be stopped for 30 minutes with cardioplegic solutions
Will prolong clotting time
Heart-lung bypass may be used to prevent/limit hypoxic brain damage
Three methods
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Surface: Immerse patient in icewater or wrap in an icewater recirculating
blanket
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Body cavity: Pour icedsaline into body cavity (slow)
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Extracorporeal: Run blood through a heat exchanger
Electronarcosis
Delivered via electrodes applied to the head
Activates opioid or nonopioid control centers in the brain
Induction characterized by convulsions unless muscle relaxants are administered
Difficult to monitor and of questionable humaneness both for restraint or
anesthesia
Acupuncture
Points may be stimulated with needles, saline injection, electric stimulation, or
metal implantation
Useful for treatment of chronic pain but not recommended for anesthesia (due to
inadequate analgesia and lack of known needle placement sites for specific
procedures)
 Section 2.11: Local and Regional Anesthesia
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May be used on topical mucous membranes
Lidocaine, proparacaine, benzocaine, tetracaine, and butacaine are examples
Useful for intubation and eye examination/procedures
 20% Benzocaine not recommended for intubation gel
 Cetacaine is 14%
 Recent literature suggests that it may cause methemoglobinemia
(hemoglobin is oxidized and unable to carry oxygen)
May be administered as a solution, in a gel, or as an aerosol
May be used as a topical anesthetic
Ethylchloride will freeze small areas and cause loss of sensation
Potocaine cream penetrate skin
EMLA cream (lidocaine and prilocaine) requires 45-60 minutes for penetration
(in humans)
32
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May be used on muscles exposed at the surgical site
May be used as an injectable local anesthetic
Most reliable and safest method
Lidocaine is the most common
Injected SC or ID
Mepivicaine or procaine (w/o epinephrine) may be used
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Epinephrine may cause local ischemia and necrosis
May be used as a field block
Skin is blocked first and then anesthetic infiltrated into deeper areas
May be used as a local nerve block
Lidocaine is commonly used
Common techniques:
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Ring block: Inject around the circumference of a limb to provide analgesia
for the distal portion
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Brachial plexus block: Injected medially to the shoulder joint
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IV Regional: A tourniquet is placed proximally from the surgical site on a
limb and lidocaine is administered at the site
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<90 minutes duration appears safe
May be used as an epidural anesthetic
Lumbosacral (L7S1) is the common site of epidural administration
Excellent for procedures caudal to the umbilicus
Useful for cesarean section as it will not depress the infant’s systems
Allows conscious animal to care for babies
Check for CSF or blood flow into needle prior to injection
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Blood indicates puncture of the central venous plexus
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CSF indicates subarachnoid puncture
Lidocaine or bupivicaine commonly used
May be injected continuously via threaded plastic catheters
Opioids injected into epidural space induce profound analgesia
Intercostal nerve blocks
This affects at least two adjacent intercostal spaces because of nerve supply
overlap
General muscle blocks
Injected into muscles that will be cut, separated, or subject to extensive
manipulation during surgery
May be used interpleurally
Useful for reducing pain after trauma to ribs or a thoracotomy
Injected into the pleural space
Ineffective if miss-administered into an adjacent space
 Section 12.12: Inhalation Anesthesia Equipment
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Anesthetic Delivery Systems:
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Inhalant anesthetic agents commonly require an anesthesia machine for delivery
of the agent
Ether, methoxyflurane, and chloroform may be administered via a soaked cotton
mask, gauze or placing small animals in a chamber with anesthetic soaked gauze
Difficult to control administration and may be dangerous
Animals may also be placed in a chamber where anesthetic gas is introduced from
an anesthetic machine
The anesthesia machine should either be attached to a passive or active
scavenging system for collection of waste gasses or the animal should be
anesthetized in a ventilated fume hood
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Two types of anesthesia machines; VOC and VIC systems
Vaporizer Out of Circuit (VOC system)
The most common style of anesthesia machine
Allows more precise control over the concentration of the inhalant gas in the gas
mixture administered to the animal
Gas Passage Through a VOC System
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Oxygen is delivered via a tank into the machine through a regulator
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Using a double circuit ventilator, a Y-piece allows oxygen to pass to the
chamber outside the bellows as part of the Driving Gas Circuit
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Oxygen passes through a flowmeter, allowing adjustment to the flow rate
and pressure of oxygen through the system
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Oxygen then passes through an anesthetic vaporizer where the agent is
introduced in known concentrations into the oxygen stream (or other
carrier gas)
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Oxygen/anesthetic mix passes through a unidirectional inhalation valve
into an inhalation breathing tube
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An air intake valve above this valve allows air to enter the system if
oxygen flow is disrupted
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A reservoir bag is attached below to meet peak inspiratory demand and
compliance during exhalation
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Allows assisted or controlled ventilation
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With a double circuit ventilator the reservoir bag is replaced with a tube
leading to the ventilator bellows for collection and pumping of the air
through the breathing circuit
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Oxygen/anesthetic mix is passed into the animal via inhalation or
ventilator pressure
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Animal exhales waste gas
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Waste gas enters the exhalation breathing tube and overflow gas passes
through a popoff valve to an exhaust system
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Popoff valve allows the system pressure to be adjusted
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With ventilators, outflow goes to the ventilator for pressure requirements
and scavenging system is attached to it
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The rest of the gas passes through the absorber and CO2 is absorbed
before the gas mixture continues the circle
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Absorber has a manometer above to measure the pressure in the system
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>20-25 mm Hg is potentially dangerous as it may prevent CO2 absorption
Vaporizer In Circuit (VIC system)
Vaporizer more passively allows anesthetic to be absorbed into the oxygen stream
Does not allow precise control of the agent concentration in the oxygen and thus
to the patient
Interesting in that the faster the animal breathes (spontaneous ventilation) or with
the use of positive pressure ventilation the animal gets an increased amount of
anesthetic agent delivered over a given time period
 Animal begins to recover, breathes faster, gets more anesthesia as
the concentration in the gas mixture increases without any operator
adjustment
No longer produced in the USA
35
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Vaporizers:
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Physics of vaporization
Heat energy is required for vaporization
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Latent heat of vaporization: the number of calories needed to change 1
gram of liquid to vapor
This heat requirement causes cooling of the anesthetic during vaporization
Vapor pressure of an anesthetic is the partial pressure (PP) of the anesthetic gas
above the liquid at equilibrium
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Vapor pressure varies with temperature
Uncontrolled cooling limits the vaporizer’s output
Vaporizers are typically made using materials with a high specific heat that
supplies heat to the liquid and retards cooling
High thermal conductivity also passes heat from the room to the liquid
Copper and bronze are most commonly used due to favorable values of heat
production and transmission
Vaporizers must also compensate for flow, temperature, and pressure
Material supplies a “heatsink”
Some vaporizers may be heated to provide the higher amounts of heat energy
required to vaporize the anesthetic agent; i.e., desflurane
Various methods of backpressure compensation are used
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 Mechanical Ventilation:
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Air enters (A) and compresses bellows and forces air along circuit into patient
system (C)
Overflow gas from the patient exits via popoff valve (E) to scavenger (B)
Adjustment of tidal volume control (F)
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Bellows may be ascending or descending
Ascending is safer as it will collapse if the circuit is opened, descending will
continue functioning
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Operator may not know that there is a problem
Collapsed bellows are immediately apparent
Intermittent Positive Pressure Ventilation (IPPV): Airway pressure is maintained
above ambient pressure during inspiration and falls to ambient pressure to allow
expiration
Conventional Positive Pressure Ventilation (CPPV): Form of IPPV where a preset
tidal volume is delivered at a preset frequency
Positive End Expiratory Pressure (PEEP): Endexpiration pressure is maintained
higher than the ambient pressure
Continuous Positive Airway Pressure (CPAP): Airway pressure is maintained
above ambient pressure during SPONTANEOUS respirations
Intermittent Mandatory Ventilation (IMV): Used during weaning from a
ventilator this allows spontaneous breathing while providing lowered tidal
volumes and/or rates
The periodic “sigh” that the anesthetist provides is also termed IMV
CO2 Absorber
Absorbs CO2 before gas passes to the patient side of the circuit
Canister should be large enough to contain a gas volume equal to or greater than
the patient’s maximum tidal volume around the granules
Commonly filled with sodium lime or barium hydroxide lime
Lime will expend itself and stop absorbing CO2
May change color or harden
Color can change back during storage without allowing further absorption
Weight is a better indicator of absorbent saturation than color
Lime will also heat up if working properly (heat line)
Mapleson Systems
Do not use chemical absorbent for CO2 but instead rely on high flow rates
Requires more gas and promotes hypothermia and drying of the respiratory
system
Commonly called nonrebreathing systems
Useful for smaller species where the system volume of a standard circuit is too
high
Two main styles; Magill and Bain Coaxial Systems
Magill system
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Efficient during spontaneous ventilation
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Fresh gas flow should approximate the patient’s minute volume
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Volume of the tubing and bag should be equal to or greater than the
patient’s tidal volume
37
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Bain coaxial system
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A tube within a tube
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Popoff valve incorporated in the bag
 Scavenging Systems:
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Exposure to waste gasses is a significant concern and health risk
Scavenging systems have three parts
Gas collecting assembly gathers waste gasses from the system, typically the
portion exiting from the popoff valve
Interface prevents transfer of pressure changes in the scavenging system to the
breathing system
Disposal system can be passive or active

Both may eliminate waste gasses by venting to the atmosphere or by
passing the waste gas through activated charcoal devices
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Activated charcoal does not absorb N20
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Passive gasses rely on the pressure within the breathing circuit from
oxygen flow and respiration to push waste gasses through the system
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Active devices typically have draw fans that provide low negative pressure
and actively draw waste gasses through the system
38
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Active devices are generally safer and allow less anesthetic gas to be
released into the room
 Section 12.13: Respiration and Ventilation
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Respiration: the total process whereby oxygen is supplied to and utilized by body
cells and CO2 is eliminated by means of concentration gradients
Ventilation: movement of gas in and out of the alveoli in the lungs
Eupnea: ordinary quiet breathing
Dyspnea: labored breathing
Tachypnea: increased breathing rate
Hyperpnea: fast and/or deep respiration, indicating “overrespiration”
Polypnea: rapid and shallow (panting) breathing
Hypopnea: slow and/or shallow breathing, indicating “underrespiration”
Apnea: transient or longer cessation of breathing
Cheyne-Stokes respirations: initial increase in rate and depth, followed by
slowing followed by brief periods of apnea
Biot’s respirations: sequence of gasping, apnea, and several deep gasps
Kussmaul’s respirations: regular deep respirations without pause
Apneustic respirations: long, gasping inspirations with several ineffective
exhalations
Tidal Volume (VT): volume of air inspired or expired in a single breath
Inspiratory Reserve Volume (IRV): volume of air that can be inspired over and
above the normal tidal volume
Expiratory Reserve Volume (ERV): amount of air that can be expired by forceful
expiration after a normal expiration
Residual Volume (RV): air remaining in the lungs after the most forceful
expiration
Minute Respiratory Volume or Minute Ventilation (VE): VT times Respiratory
Frequency (f)
Pulmonary Capacities:
Inspiratory Capacity (IC): tidal volume plus the IRV. Amount of air that can be
inhaled starting after a normal expiration and distending the lungs to the
maximum amount
Functional Residual Capacity (FRC): ERV plus RV. Amount of air in the lungs
after a normal expiration
Vital Capacity (VC): IRV plus VT plus ERV. Maximum amount of air that can be
expelled from the lungs after first filling them to maximum capacity
Total Lung Capacity (TLC): IRV plus VT plus ERV plus RV. Maximum volume
to which the lungs can be expanded with the greatest possible inspiratory effort
Ventilation Basics
Gas transfer: is the passing of gasses back and forth across a bodily membrane
Dependant on a pressure gradient between alveoli and outside atmosphere
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During inspiration active muscular effort is used to expand the thoracic wall and
contract of the diaphragm
Expiration is a passive process where the chest wall returns to a normal position
Exception is the horse, where abdominal muscle contraction is used (biphasic
mode of exhalation)
Air flow is dependant on the diameter of the passages
Smaller the diameter, the greater the resistance to flow
Alveolar air is the critical component.
Not equal to minute volume as a large portion fills the respiratory passages
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This volume is the Dead Space Volume (VD anat) and fills the Anatomic
Dead Space
Gas is transferred to/from the blood via pressure gradients
Under general anesthesia, nasal and pharyngeal musculature relaxes
May allow obstruction
 Section 12.14: Inhalation Anesthesia
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Differ from all other anesthetic agents because they are administered through and
mostly eliminated from the lungs
They favor rapid and predictable changes in anesthetic depth
Generally require an oxygen source and a patient breathing circuit
Latter generally includes an endotracheal tube/face mask, a means of eliminating
CO2, and a compliant gas reservoir
 Historical Inhalant Agents
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Chloroform
May cause liver failure
Cyclopropane
Explosive
Diethyl ether
Widely used until ~20 years ago
Replaced due to flammability
Fluroxene
Trichlorethylene
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All but nitrous oxide are organic compounds
Subdivided into:

Aliphatic hydrocarbons: Halothane

Ethers (2 organic radicals connected by an oxygen atom): Enflurane,
Methoxyflurane
Found that the lack of an ether group leads to an increased chance of cardiac
arrhythmias
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Reason that all posthalothane agents are ethers
Gas and Vapor are the two physical forms of inhaled anesthetics
 Inhalant Agent Characteristics
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Gas: an agent that exists in gaseous form at room temperature and sea level
atmospheric pressure (nitrous oxide)
Vapor: an agent that is gaseous in form while being a liquid at ambient
temperature and pressure (all others)
Composed of molecules bouncing about at high speed
Impact of bouncing molecules on container walls creates a force called pressure
Boyle’s law: the smaller the container for a given volume of gas, the more
bombardments against the vessel wall in a given area and thus higher pressure
Charles’s law: increase in temperature will give more energy to the molecules, so
that they move more and thus increase pressure as well
Made up of molecules bouncing about at high speed
Dalton’s Law of Partial Pressure: Pressures of each gas in a mixture of gasses
(called partial pressure) in a mixture added together is the total pressure
Quantities of agent can be characterized by pressure, concentration, or mass
Commonly use concentration (% of volume)
Vapor Pressure
All molecules are in motion
Some in surface layer will break free and enter the vapor phase (vaporization or
evaporation)
Will progress to equilibrium
These molecules exert force like a gas
At any specific temperature there is a maximum amount of vapor that can exist
for a given liquid volume (saturated vapor pressure)
Primary difference between gas and vapor is that a gas can mix with another gas
in concentrations up to 100%
Vapor can only exist in concentrations up to the ceiling imposed by the vapor
pressure
Temperature
Heat imparts more energy to liquids, allowing more molecules to escape and thus
increasing amount of vaporized liquid
Boiling point
Temperature where vapor pressure is equal to atmospheric pressure
Liquid becomes a gas
Solubility
Molecules randomly bounce into liquid
Continues until equilibrium outside and inside the liquid is present
Important because agent solubility in body fluid and tissue determines anesthetic
amounts, effectiveness, and pharmacokinetics
Partition Coefficients (PC)
Difference between the concentration of agent in one liquid/area and another at
equilibrium
Blood/brain, gas/blood, blood/lipid, etc.
Pharmacokinetics
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Goal is to place an adequate partial pressure of anesthetic in the brain to cause the
desired level of CNS depression
Agents move down a series of partial pressure gradients (PPG) to the target tissue
as well as other tissues
Agent is delivered with O2 to the alveoli
Must reach appropriate Inspired Concentration
IC is a factor of circuit volume
Larger the circuit volume, the longer it takes the concentration of gas leaving the
vaporizer to be reflected in the animal portion of the circuit
Solubility of the agent in the circuit materials will also have an effect
Greater the amount of agent delivered to the alveoli (function of respiration rate
and pressure) the greater the Alveolar Ventilation
Agent moves along PPG into the blood
A low blood solubility (PC) requires less agent to reach blood equilibrium and
then start passing to other tissues
Once in the blood, agent must travel to target tissues
Greater vascularity in certain tissue, the greater amount of blood available for
agent transfer
Function of cardiac output
Biotransformation
Some agent is metabolized
May help in recovery (older agents)
May cause acute and chronic toxicities in certain organs
Minimum Alveolar Concentration (MAC) is the amount of agent required to
produce immobility in 50% of healthy subjects
Inversely proportional to potency
Refers to % at the alveoli, not at vaporizer or in circuit
Gas Cylinders
Oxygen
Anesthetized animals have higher O2 requirements and have a reduced tidal
volume
Greater oxygen % in breathed gasses important for adequate supply
Can be in supplied in gaseous form or as a highly pressurized liquid
CO2
Usually used for rodent immobilization or euthanasia
May be mixed with oxygen for less irritation (controversial)
Nitrogen
Used for powering drills and other equipment
Breathing Air Mixture
Mix of gasses similar in composition to normal room air
Gas cylinder safety
O2 and N2O gasses support combustion
Sudden release of gas from a broken cylinder may cause injury or propel other
pieces of equipment so as to cause injury
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Broken tank or valve might also create a heavy rocketlike projectile
Gas cylinder safety:
Tanks are typically unbalanced and possess a small base
Tanks should be chained to a wall or cart at all times
Regulators should be capped when not attached to gaslines
Should be stored away from emergency exits and high traffic areas
Note: Tank colors are NOT truly standardized and may vary in color from
manufacturer to manufacturer
Unlabelled tanks should not be used
 Inhalant Anesthetics:
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Nitrous Oxide
Tank is filled with liquid N2O under 750770 psi.
Some gas is present and is taken off when the tank is opened
As gas escapes, more liquid converts to gas until all liquid is removed
Thus, pressure of the gas will not change as gas is removed
When nothing is left in the tank but gas, the pressure decreases as gas is removed
Why weight is better than pressure to gauge amount left in tank
MAC is above 100%
Cannot deliver sufficient N2O for anesthesia and leave room for oxygen
Must be combined with another agent to help lower its required amount
Nitrous oxide/oxygen ratio should never exceed 3:1 or insufficient O2 will be
delivered
Has rapid onset of action due to low blood solubility
Has minimal cardiovascular, liver, and kidney effects
May transfer to organs or body areas and cause pneumothorax, a blood embolus, a
pressure increase in the middle ear, and pneumocephalogram
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When N2O administration is stopped it floods into the lungs, displacing O2
(diffusion hypoxia)
Interferes with CO2 monitoring
Halothane
Good potency
Has high volatility
Rapid onset of action
Can be delivered as up to 33% of an inspired gas mixture (which can be fatal at
the upper level)
Causes respiratory depression
Depresses myocardial muscle
Relaxes vascular smooth muscle
Increases cerebral blood flow (vasodilation)
Mixed with thymol for stability
Thymol is less volatile and will accumulate in devices and causes malfunction
unless regularly cleaned
Ether
The principal inhaled anesthetic agent prior to development of the later
nonflammable agents
Concentrations used for anesthesia are explosive
Patients will release sufficient quantities of ether to be flammable or explosive
even after death
Highly irritating to the respiratory tract
Methoxyflurane
Has low volatility and high blood solubility
Therefore safe in nonprecision systems
Is extensively metabolized
Respiratory depressant
Has slow onset and recovery
Isoflurane
Low solubility and high potency
Rapid induction and recovery
Less cardiovascular effects than halothane
Greater safety margin than halothane in rats
Potent coronary vasodilator
Hyperventilation prior to administration will limit cerebral blood flow increases
Minimal chance of renal or kidney injury
Desflurane
Effects similar to isoflurane
More of a respiratory irritant than isoflurane
Has lower solubility in blood than isoflurane, halothane, or methoxyflurane
Allows rapid equilibrium for quick and precise changes in depth of anesthesia
Very rapid induction and recovery
Has a low boiling point and thus requires a special heated vaporizer
44
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Sevoflurane
Effects similar to isoflurane
Has lower solubility in blood than isoflurane, halothane, or methoxyflurane
Allows rapid equilibrium for quick and precise changes in depth of anesthesia
Very rapid induction and recovery
 Section 2.15: Monitoring Anesthesia
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Why Monitor?
Anesthetic drugs compromise the patient’s physiological homeostasis
Monitoring allows the evaluation of physiological feedback from the animal to
properly maintain the desired level of anesthesia
Allows early notice of trends which may develop into lifethreatening conditions
Ultimately gives the anesthetist the information to provides better and more
precise anesthesia
Proper Monitoring Allows
Adequate anesthesia/amnesia
Adequate analgesia
Adequate immobilization
Monitoring Adequate Anesthesia and Amnesia
Evaluate muscle tone and reflexes
Signs may vary between species and individuals
These signs can vary from minute to minute during a procedure
Information should be evaluated based on the animal’s reactions and parameters
at that instant
Previous readings are useful for trends but should not be relied on over “current”
readings
General anesthetic doses are dependant on the induction drug type, effect,
duration of action, and amount administered and the animal’s health condition
Adequate Analgesia
If the animal is sufficiently anesthetized (unaware/detached from external stimuli)
then it may be concluded that sufficient analgesia is present
Remember, paralytics may cause an animal to appear anesthetized on cursory
exam but still feel pain
Light anesthesia may not completely suppress reflexes or spontaneous movement
even though analgesia is achieved
Adequate Immobilization
Based on muscle tone
Defined based on needs of the surgical procedure
Slight movement that does not interfere with the procedure is acceptable
Intraocular procedures, thoracic procedures, longbone fracture repair procedures,
and procedures involving extensive laparotomies generally need complete muscle
relaxation
Neuromuscular blocking agents may be safer than overly deep anesthesia
45
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Physiological Effects of Anesthetic Drugs
Pharmacodynamic effects may vary but the mechanisms are usually the same
Excessive hypotension, bradycardia, arrhythmias, myocardial depression,
vasodilation, vasoconstriction, hypoventilation, hypoxemia, etc.
Preanesthetic exams (baseline values) should provide clues as to which conditions
are already present as well as to alert the anesthetist to potential trouble areas
Specific physiologic values should be evaluated by looking at the parameter’s
previous trends, combined with other parameters, and with consideration of the
patient’s history
Pulmonary Monitoring
Normal respiratory rates can vary widely
Should be evaluated along with tidal volume and respiratory trends
May indicate an underlying physiologic change
Tachypnea (accelerated breathing)
Too lightly anesthetized
Too deeply anesthetized
Hypoxemia
Hypercapnia
Hyperthermia
Hypotension
Atelectasis
Drug effects
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Individual variation
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Arrhythmic breathing patterns are usually the effect of a medullary
respiratory control problem
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However, some abnormal patterns may be normal in certain species
A Cheyne-Stokes (an abnormal breathing pattern that is first shallow and
infrequent and then increases gradually to become abnormally deep and rapid,
before fading away completely for a brief period. Breathing may be stopped for
about 5 to 30 seconds, before the next cycle of shallow breathing begins) pattern
is normal in horses but may be a sign of congestive heart failure or other heart or
brain disorders
Apneustic breathing (inspiratory hold) may be seen in healthy cats, dogs, and
most species anesthetized with ketamine
Respiratory volume may be estimated visually, by reservoir bag inflation, or by
using a ventilator or ventilometer
Normal tidal volume is 10-20 mL/kg/respiration
Normal total minute ventilation (TMV) is 150-250 mL/kg/min
Alveolar minute volume may range from 20-70% of TMV
Arterial CO2 and O2 levels may be analyzed by taking arterial blood and
measuring with a blood-gas analyzer
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Venous blood has a tissue bed between it and the lungs where gas
exchange takes place and thus is not a good measure of respiratory
function
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Samples should be run immediately or stored in ice water
Partial Pressure of CO2 (PaCO2)
Measures ventilatory status of the patient
Normally ranges between 35 and 45 mm Hg
PaCO2 over 60 mm Hg indicates excessive respiratory acidosis and may warrant
mechanical ventilation
PaCO2 under 20 mm Hg may be a sign of severe respiratory alkalosis and
decreased cerebral blood flow
Venous CO2 is usually 3 to 6 mm Hg higher than arterial CO2
PaCO2 may be estimated by measuring end tidal CO2
A lowered level is hypocapnia
Most often caused by hyperventilation
An elevated level is hypercapnia
May be caused by:
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Excessive anesthesia depth
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Intracranial disease or cervical disease
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Airway obstruction
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Thoracic or abdominal restrictive disease
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Pleural space filling disorder (air or fluid)
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Terminal pulmonary parenchymal disease
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Miss-set ventilator settings
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Hyperthermia
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Recent bicarbonate therapy
Normal level is eucapnia
Endtidal CO2 (ETCO2) is the CO2 sample taken from the breathing circuit at the
end of an exhalation
Accuracy is subject to mechanical factors with the breathing circuit such as
volume, dead pockets, tubing diameter, gas flow, etc.
Usually somewhat lower than PaCO2
Plateau with a drop to the right may indicate a leak in the circuit as the pressure of
inspiration is not held
Animals with ETCO2 over 30-40 mm Hg will usually breathe on their own
Some hyperventilation is necessary during mechanical ventilation to prevent overbreathing the ventilator
Values should be kept between 25 and 30 mm Hg
Towards the end of the procedure, the animal should be weaned off the ventilator
to restart spontaneous respiration.
Gradually slow the rate and/or volume to increase ETCO2 to over 30 to 35 mm
Hg
During open-skull procedures, values between 18 and 20 mmHg will help prevent
brain swelling
 Cardiopulmonary Monitoring
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Partial pressure of O2 (PaO2)
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Measures the oxygenating efficiency of the lungs
Is a measure of the oxygen dissolved in the blood and is related to hemoglobin
saturation (SaO2) but is not the same thing
Usually 80 to 110 mm Hg
Pulse Oximetry
Measures the percentage of oxygenated hemoglobin and the heart rate
Sensor beams infrared light through tissue and records the absorption either of
light passing through the tissue to a receiver on the other side (transmission) or
reflected back to the sensor (reflectance)
Other tissues also absorb light and thus pulse oximeters have a variety of
computational ways to interpret the data
Is broadly accurate for SaO2
Normally SaO2 is 8090% in spontaneously breathing animals and 95100% in
ventilated animals
Numbers reflect animal on 100% oxygen
SaO2 readings are susceptible to lowering by positional factors (slipping away
from tissue, thick tissue, pigment), vasoconstriction, drying of contact surface,
and confusion with respiratory artifact
HR in anesthetized dogs usually ~60 bpm
HR in anesthetized cats usually ~100 bpm
Venous Admixture
Collective term for all of the ways blood can pass from venous return to arterial
supply without being properly oxygenated (hypoxemia)
Equipment problem/decreased oxygen inspiratory supply, hypoventilation,
bronchoconstriction, atelectasis, inhalation toxicity (diffusion impairment), and
anatomic right-to-left shunt
Electrocardiogram (ECG)
Monitoring heart function
Life-threatening situations include
Tachycardia: rates higher than 160-180 bpm in cats and dogs
Bradycardia: rates less than 60-70 bpm in dogs and 100 bpm in cats
Heart Block: loss of or non-P-wave associated QRS complexes
Indicate lack of electrical transmission in the heart
PVC's: Indicate dangerous arrhythmias
Fibrillation: indicates cardiac arrest has begun to occur
P Wave is the impulse conduction from SA Node
QRS Complex is the ventricular depolarization that precedes contraction
T Wave is ventricular repolarization
PR Interval lasts from the beginning of atrial excitation to the beginning of
ventricular excitation
QT Interval is the period of ventricular depolarization and repolarization
U Wave
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Uncertain of origin
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Relatively uncommon
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More common in larger species
ECG Rates and Arrythmias
Bradycardia is slowed heart beat (typically >25% from normal)
Tachycardia is accelerated heart beat (typically >25% from normal)
Arrythmias are abnormal depolarization, repolarization, and/or contraction of the
heart as seen with an ECG
Common Arrythmias
Sinus Tachycardia
P wave seen more closely than normal after the T wave
May be described as “T on P”
Somewhat common and not typically dangerous except in compromised patients
or if it reflects inadequate coronary blood flow
Premature Ventricular Contraction (PVC)
Commonly caused by hypoxemia and/or hypercarbia and traumatic myocarditis
Single PVCs are not usually a problem but a series may result in decreased
cardiac output and coronary perfusion which may result in ventricular fibrillation
Ventricular Fibrillation
A pulseless arrhythmia with irregular and chaotic electrical activity and
ventricular contraction in which the heart immediately loses its ability to function
as a pump
Little or no blood is pumped from the heart
Sudden loss of cardiac output, with subsequent tissue hypoperfusion, creates
global tissue ischemia; brain and myocardium are most susceptible.
Primary cause of sudden cardiac death (SCD)
Ventricular Fibrillation (Cont.)
Can be counteracted by electrical current (defibrillation)
Defibrillation is not always effective and may cause burns and permanent damage
to the heart
Reflexes
Palpebral (blink): begins to be lost at stage 3 of anesthesia
Swallowing: many animals will continue to swallow under light anesthesia
Endotracheal tubes should not be removed until this reflex returns
Pedal Reflex: reaction to pinching a digit or footpad
Ear Flick: Particularly useful in cats
Corneal: Present until stage 3 plane 4 of anesthesia
Laryngeal: May cause laryngospasm in cats
Peripheral Perfusion
Capillary refill time
Measures the time taken for refilling blanched mucus membranes
Observe the color of mucus membranes
CRT should be 12 seconds and gums (when not pigmented) should be pink
Other sites for color are tongue, buccal mucous membrane, conjunctiva of the
lower eyelid, and the mucous membranes about the prepuce or vulva
Pale membranes indicate poor perfusion, blood loss, or anemia
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Purple/blue membranes indicate cyanosis
Central Venous Pressure
Luminal pressure of the intrathoracic vena cava
Generally measuring catheters placed via the left jugular vein into the anterior
vena cava
Don’t touch the endocardium of the right atrium
May stimulate ectopic pacemaker activity
Normally 0 to 10 cm H2O
15 to 25 in laterally recumbent horses
5 to 10 in dorsally recumbent horses
Arterial Blood Pressure
Peripheral artery pulse amplitude quality may not closely match central arterial
blood pressure
Indirect blood pressure
Indirect Sphygmometry
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Monitored with a pressure cuff about an appendage
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Cuff should be 40% as wide as the circumference of the limb
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If too tight, the cuff will partially occlude blood flow and artificially lower
the value
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If too loose, the cuff will require increased cuff pressure for contact and
the value will be artificially high
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Cuff should be inflated until it is at a higher pressure than systolic
pressure, where it occludes the arteries
Doppler piezoelectric crystal
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Crystal is placed over the artery
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Transmits energy whose frequency changes based on the movement of the
underlying tissue
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Closely correlates with direct arterial measurements
Oscillometric
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Measures intracuff pressure over several inflations and deflations
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Provides an averaged reading of systolic pressure, diastolic pressure,
mean, and rate
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The standard style for mechanical blood pressure monitors
Direct Blood Pressure
Involves a cannula surgically placed into an artery
A percutaneous catheter may also be placed into a peripheral artery (pedal,
carotid, femoral)
Generally attached to a aneroid manometer
Fluid filled catheters generally need flushing with heparinized saline or other
solution
Solid state catheters have no lumen but rather a pressure sensor that transmits the
signal electronically
No flushing needed
Cardiac Output
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More relevant to systemic perfusion (flow) than a pressure value
Reduced by hypovolemia, ventricular restrictive disease, decreased contractility,
bradycardia, tachycardia, arrhythmias, retrograde flow (regurgitation), and
stenosis
Generally obtained via thermodilution
Chilled saline of a known temperature and volume is flushed into the artery and
the rapidity of the resultant temperature change is measured
 Temperature
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Anesthetized animals lose the ability to thermoregulate normally
Will lose heat via loss of hair to shaving, the evaporation of prep solutions,
evaporation at and chilling of tissues within surgical incisions, and vasodilation
caused by anesthetic agents/adjuncts
Hypothermia will prolong anesthesia recovery
Should be countered with warmed fluids, heating blankets, and towels/wraps
Hyperthermia is also possible and dangerous
May be due to overheating with heating pads and tables or due to to anesthesia
reactions such as malignant hyperthermia in swine
 Part 3: Analgesia and Pain Management
 Section 3.1: Definitions
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Pain: An unpleasant sensory and emotional experience associated with actual or
potential tissue damage
Suffering: An unpleasant emotional state that is not outwardly represented
originating from either a physical or physiological source
Distress: The external expression by behavior or emotion of suffering that an
observer can see
Algology: The science and study of pain
Allodynia: Pain caused by a stimulus that does not normally provoke pain
Analgesia: Absence of pain in the presence of a stimulus that would normally be
painful
Analgesic: Drug(s) that induce analgesia
Anesthesia: Absence of all sensory modalities, can be local, regional, or total
Anesthetics: Drugs that induce regional or general anesthesia
Causalgia: Syndrome of prolonged burning pain, allodynia, and hyperpathia after
a traumatic nerve lesion, often combined with vasomotor and sudomotor
dysfunction and later trophic changes
Central Pain: Pain associated with a lesion of the CNS
Deafferentation Pain: Pain caused by loss of sensory input into the CNS, as occurs
with avulsion of the brachial plexus or other types of peripheral nerve lesions, or
caused by pathology of the CNS
Dermatome: Sensory segmental supply to skin and subcutaneous tissue
Dysethesia: An unpleasant spontaneous or evoked abnormal sensation
51
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Hyperesthesia: Increased sensitivity to stimulation, excluding the special senses
Hyperalgesia: Increased response to a stimulation that is normally painful
Hypoalgesia: Diminished sensitivity to noxious stimulation
Hypoesthesia: Diminished sensitivity to stimulation, excluding the special senses
Neuralgia: Pain in the distribution of a nerve or nerves
Neuritis: Inflammation of nerve cells or nerves
Neuropathy: Disturbance of function or a pathologic change in a nerve
Nociception: Reception, conduction, and CNS processing of nerve signals
generated by the stimulation of nociceptors. It is the physiologic process that
when carried to completion results in the conscious perception of pain
Nociceptor: Receptor preferentially sensitive to a noxious stimulus or to a
stimulus that would become noxious if prolonged
Nociceptor Threshold: Minimum strength of a stimulus that will cause a
nociceptor to generate an impulse
Noxious Stimulus: Stimulus that is actually or potentially damaging to tissue or is
of a quality or intensity to trigger nociceptive reactions
Pain Threshold: The least experience of pain that a subject can recognize. In most
cases is higher than the nociceptor threshold. Relatively constant among species
and individuals
Pain Tolerance: Greatest level of pain that a subject will tolerate. Varies
considerably between species and individuals
Pain Tolerance Range: Difference between the pain detection threshold and the
pain tolerance threshold
Paresthesia: Spontaneous or evoked abnormal sensation. Not painful, as opposed
to dysethesia
Radiculalgia: Pain along the distribution of one or more sensory nerve roots
Radiculopathy: Disturbance of function or pathological change in one or more
nerve roots
Radiuclitis: Inflamation of one or more nerve roots
Reflex: Involuntary, purposeful, and orderly reactions to stimulus. The anatomic
basis for the reflex arc consists of a receptor, a primary afferent nerve fiber
associated with the receptor, a region of integration in the spinal cord or brain
stem and a lower motor neuron leading to an effector organ (skeletal or smooth
muscle or glands)
Reaction: Combination of reflexes designed to produce a widespread movement
in relation to the application of a stimulus. Reactions are mass reflexes not under
voluntary control and therefore do not involve the cerebral cortex
Response: Willful movement of the body or parts of the body that requires
involvement of the somatosensory cerebral cortex
Somatic: Describes input for body tissues other than viscera
Somatic Pain: General nociceptor based pain
Visceral Pain: Differs from somatic pain:
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Cannot be evoked from all organs (such as the liver and kidneys)
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Not evoked by burning and cutting
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Poorly localized
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May be from nociceptors or other receptors that may have other functions
“WindUp”
Nociceptors do not demonstrate fatigue with repeated stimulation
Rather, they display enhanced sensitivity, lowered threshold of stimulation, and
prolonged and enhanced response to stimulation
Following a barrage of afferent nociceptor impulses hypersensitization of dorsal
horn cells occurs, resulting in an increased rate of discharge (windup)
In short, windup allows increased sensitization in nerve tissue to noxious
stimulus, a sensitivity that can expand in a receptive field to include distant nerves
This creates greater pain from a stimuli than it might otherwise cause
Think of it as an avalanche
Preventing windup can decrease perceived pain and allow for less analgesic
administration
Windup can be prevented through the use of local preemptive analgesics and/or
the prompt or preemptive use of general analgesics
Response to Pain and Injury
Stress responses associated with pain are still present unless blocked by epidural
or intrathecal anesthetics
Peripheral nerve blockage is not as effective
Systemic opioids have little effect
These responses can also be obtunded or largely prevented by the use of
preventative general or local analgesics
Nociceptor stimulation of medullary centers results in hyperventilation, increased
hypothalamic neural sympathetic tone, and increased secretion of catecholamines
and other endocrine hormones
Increases cardiac output, peripheral vascular resistance, blood pressure and
myocardial oxygen consumption
Cortisol and other hormones are released which causes increased blood glucose
and ketone levels and increases the rate of metabolism and oxygen consumption
Magnitude and duration of these effects parallel the degree of tissue damage
These same physiological responses occur in properly anesthetized or
unconscious patients but do not result in the sensation of pain due to a
nonfunctioning cerebral cortex
Pain also causes anxiety and fear
These psychological attitudes enhance the stress response
Cause cortically mediated increases in blood viscosity, clotting time, fibrinolysis,
and platelet aggregation
Increase cardiac work, cardiac output, oxygen consumption postsurgery when the
cardiac reserve is diminished due to the procedure
May lead to intense vasoconstriction which leads to ischemia, tissue hypoxia, and
release of substances toxic to the myocardium
May result in renal failure
Severe posttraumatic or postoperative pain may initiate shock
Control of Pain and Injury
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All of this may lead to retarded postsurgical healing
The stress response can be attenuated through adequate pain relief and supportive
therapy
Initially pain may be controlled with systemic administration of opioids and
alpha2adrenergic agents
Longterm control may require epidural or spinal administration of these drugs,
perhaps combined with local anesthetics
In addition, the results of the stress response and tissue reaction to trauma may be
treated;
Cardiovascular function may be supported by administration of fluids, blood, and
blood products
Parenteral nutrition may be supplied
Splints and bandages may reduce swelling which results in pain as well as
immobilizing the damaged area to prevent the animal causing itself pain
Corticosteroids and nonsteroidal antiinflamatories may be used
Management and Control of Pain
Structures involved in the sensation of pain are very similar in humans and
animals
Reasonable to assume that if something is painful in people, is damaging or
potentially damaging to tissues, and/or induces escape or adverse emotional
responses in the animals behavior (signs of distress, avoidance behavior,
vocalization, changes in body posture) it should be considered painful to the
animal
If a procedure may result in stimuli likely to cause pain it is appropriate to
administer preventative analgesics
Accurate selection and dosage will result in the relief of pain without severe
respiratory depression
Clinical analgesia is not the absence of pain but the clinical reduction of the
intensity of pain to a tolerable level
Balanced analgesia is the result of administration of analgesic drugs in
combination and at multiple sites to induce analgesia by altering more than one
part of the nociceptive process
Preoperative analgesia is highly effective as it;
Prevents spinal neuroplasmic changes (Windup)
Suppresses the neuroendocrine response to pain
Improves tissue healing and mobility
Is the most effective means of controlling postoperative Pain
Analgesia may be achieved by obtunding or interrupting the nociceptive process
 Interrupting the Nociceptive Process Locally

The four parts of the nociceptive process:

Transduction is the translation of noxious stimuli into electrical nerve
impulses at the peripheral nociceptor

Reduced with nonsteroidal antiinflamatories
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Transmission is the propagation of nerve impulses through the nervous
system
Local anesthetic blockage of peripheral nerves
Epidural or subarachnoid analgesics
Four parts that may be affected
Modulation: Areas where nociceptive transmission is modified by
endogenous descending analgesic systems (opioid, serotonergic and
nonadrenergic) which inhibit spinal dorsal horn cells
Epidural or intrathecal opioids
Administration of alpha2agonists
Perception is the final conscious subjective and emotional experience of
pain
Not controllable in animals
In humans, meditation and other metal techniques may be used
 Section 3.2: US Regulations
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USDA (Animal Welfare Act)
Applicable section is from the Regulations and Standards in the Code of Federal
Regulations (CFR) in Title 9 C.F.R., Chapter 1, Subchapter A Animal Welfare,
Section 2.31
Defines a painful procedure as “any procedure that would reasonably be expected
to cause more than slight or momentary pain or distress in a human being to
which that procedure was applied, that is, pain in excess of that caused by
injections or other minor procedures”
Requires that the IACUC ensure that distress and pain will be avoided or
minimized to the degree possible
USDA (Animal Welfare Act)
“Procedures that may cause more than momentary or slight pain or distress to the
animals will:
(A) Be performed with appropriate sedatives, analgesics or anesthetics, unless
withholding such agents is justified for scientific reasons, in writing, by the
principal investigator and will continue for only the necessary period of time;
(B) Involve, in their planning, consultation with the attending veterinarian or his
or her designee;
(C) Not include the use of paralytics without anesthesia”
Requires veterinary consultation or guidance concerning procedures involving
pain and distress
In the event that the IACUC committee determines that there are justified
scientific reasons for the withholding of analgesic drugs these procedures will be
allowed for the minimum necessary period
NIH (Guide for the Care and Use of Laboratory Animals)
Less specific than the USDA
55
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References the book Recognition and Alleviation of Pain and Distress in
Laboratory Animals by the Committee on Pain and Distress in Laboratory
Animals
States that different species express pain and suffering in different ways so
personnel must be familiar with species specific and individual expressions of
pain
Specifies that sedatives, anxiolytics, and neuromuscular blocking agents are not
analgesics and must not be used as such
PHS (Public Health Service)
Implements the Policy on Humane Care and Use of Laboratory Animals (which
implements the Health Research Extension Act of 1985 and the U.S. Government
Principles for the Utilization and Care of Vertebrate Animals Used in Testing,
Research, and Training)
 Section 3.3: Recognizing and Assessing Pain
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Difficult to quantitatively measure
Requires careful observation and experience in the behavior of the species as well
as the individual animal’s behavior
Many animals will not exhibit obvious signs of mild to moderate pain
Some signs of pain may also be seen in healthy animals
Cats hissing and scratching
Nonhuman primate aggression
Pain may also be seen physiologically
Vasoconstriction
Increased heart rate, blood pressure, and cardiac output
Rapid, shallow breathing
Increased plasma concentrations of epinephrine, norepinephrine, cortisol, glucose,
glucagon, lipids, ketones, and amino acids
Decreased plasma concentrations of phosphorus, magnesium, testosterone, insulin
Signs of Mild to Moderate Pain
Mouse Partially closed eyelids, rough hair coat, hunched posture, scratching,
increased aggression and apprehension, vocalization when handled, selfmutilation
Rat Partially closed eyelids, rough hair coat, scratching, increased aggression and
apprehension, vocalization when handled, porphyrin staining around eyes and
nose
Guinea Pig Sunken and dull eyes, respiratory changes, increased timidity and
sleepiness, arched back, increased vocalization when handled
Rabbit Ocular discharge, constipation or diarrhea, depression, excessive
grooming, stretched posture, tooth grinding, dull attitude or aggression
Nonhuman Primate Most signs hidden, decreased activity and food and water
consumption
Dog Decreased alertness, stiff posture, panting, licking, biting, increased
aggression and vocalization
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Cat Increased aggression, decreased food consumption, excessive
licking/grooming
Pig Changes in gait and posture, increased handling avoidance, increased
vocalization
Sheep/Goat Lying with extended legs, stamping feet, mild ataxia, depression,
restlessness, tooth grinding, increased aggression

Sheep are more stoic and less prone to display signs of pain
Signs of Severe or Chronic Pain
Mouse Weight loss, dehydration, soiled coat, sunken eyes, sunken or distended
abdomen, hunched posture, ataxia, hypothermia, decreased vocalization, wasting
of back muscles
Rat Closed eyes, weight loss, dehydration, soiled coat, sunken or distended
abdomen, ataxia, hypothermia, decreased vocalization, wasting of back muscles,
incontinence, a recumbent position with tucked head, selfmutilation
Guinea Pig Weight loss, scaly skin, dehydration, decreased timidity,
unresponsiveness, excessive salivation, increased barbering, loss of righting
reflex, decreased vocalization, hypothermia
Rabbit Tooth grinding, weight loss, dehydration, wasting of lower back muscles,
fecal staining, decreased night feces production, general unresponsiveness
Nonhuman Primate Huddled or crouching posture, clenching or grinding teeth,
anorexia, weight loss, decreased grooming, decreased socialization, increased
aggressive attention from other NHPs
Dog Crouched posture, unwillingness to move, depression, increased aggression,
vocalization when handled, increased restlessness
Cat Hunched, crouching, or stretched posture, increased aggression, anorexia,
weight loss, vocalizing, wild escape behavior, unkempt appearance, stiff gait
Pig Depression, unwillingness to move, attempts at hiding, anorexia, decreased
socialization
Sheep/Goat Rolling, frequent looks or kicks to abdomen, falling over, walking
backward, rapid and shallow respirations, weight loss, tooth grinding, grunting,
vocalization at handling, rigidity, an unwillingness to move
 Section 3.4: Analgesic Drugs
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Have as their primary effect the suppression of pain
Markedly variable effects among different species for some classes of drugs (i.e.,
opioids) due to concentrations of receptors that are independent of
pharmacokinetics of the drug
Six main types of analgesic drugs:

Opioids
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Salicylates
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Paraaminophenol derivatives

Nonopioid, nonsalicylate
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Local anesthetic agents

Alpha2adrenergic agents
57
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These are somewhat arbitrary categories and may differ between different
references
Opioids
Morphine, meperidine, methadone oxymorphone, pentazocine, butorphanol,
nalbuphine, burprenorphine, fentanyl
Induce CNS depression accompanied by miosis, hypothermia, bradycardia,
respiratory depression in primates, dogs, rats, and rabbits
Induces CNS stimulation, mydriasis, panting, tachycardia, and hyperkinesis in
horses, cats, ruminants, and swine
Depress respiratory and cough centers
May induce nausea and vomiting
Mice and rats quickly develop tolerance
Well absorbed from GI, IV, SC, IM, IT, and in some cases even transdermally
Raise the pain threshold or decrease the perception of pain at the CNS
Alter the emotional component of pain to make it more tolerable
Drugs of choice for severe, acute pain
Most provide analgesia within 30 minutes
Have relatively short half-lives
Usually on the order of 24 hours
Butorphanol: 45 hours
Buprenorphine: 812 hours
Fentanyl transdermal systems
Require application at least 12 hours prior to analgesia need for adequate blood
levels
Diffusion increased significantly by heat
Most are Schedule II Narcotics
Salicylates
Aspirin is the primary salicylate
Initially stimulate the CNS followed by depression
Stimulate respiration
May induce nausea and vomiting
Usually administered orally
Half-life dose dependant, larger the dose the longer the half-life due to liver
salicyluric acid production limitations
Are NSAIDs (Nonsteroidal antiinflammatory drug)
Inhibit prostaglandin production at damaged tissue
Prostaglandins increases nociceptor sensitivity to stimuli
Effective against lowtomoderate intensity pain
Not effective against hollow viscera pain
Paraaminophenol Derivatives
Acetanilid, acetaminophen, phenacetin
Similar to aspirin
Weak antiinflammatory effects
No CV or respiratory effects at therapeutic levels
58
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Usually administered orally
Are NSAIDs
Nonopioid, Nonsalicylate
“Everything else”
Phenylbutazone, dipyrone, meclofenamic acid, flunixin, carprofen, ketoprofen
Better tolerated in humans than aspirin
Prolong bleeding times
Biotransformed in liver and excreted in urine
Local Anesthetic Agents
Procaine, lidocaine, mepivicaine, tetracaine, bupivicaine
Used as a local anesthetic to prevent nociceptor transmission
Bupivicaine has quick onset and 46 hours duration of action
Lidocaine has quick onset and short duration of action <2 hours
Analgesia is complete at the administration sites
Alpha2adrenergic Agents
Xylazine, detomidine, medetomidine, and romifidine
Sedative hypnotics
Are potent analgesics
Decrease norepinephrine release
Combined with opioids results in enhanced and prolonged analgesia in dogs and
cats
 Part 4: Surgical Regulations and Record Keeping
 Section 4.1: US Regulations
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The Animal Welfare Act (AWA)
Passed by Congress in 1966
Administered by the United States Department of Agriculture’s (USDA) Animal
and Plant Health Inspection Service (APHIS)
Regulations administered are called the Animal Welfare Regulations
Published in Title 9 of the Code of Federal Regulations
The Health Research Extension Act (NIH) (PHS)
Taken from policy guidelines established previously by the Public Health Service
(PHS) and National Institutes of Health (NIH) in 1985
Contained in the National Regulation Council’s Guide for the Care and Use of
Laboratory Animals (commonly referred to as the Guide) and the PHS’ Policy on
Humane Care and Use of Laboratory Animals
There are minor differences between the two
PHS policy specifically implements the “U.S. Government Principles for the
Utilization and Care of Vertebrate Animals Used in Testing, Research, and
Training” developed by the Interagency Research Animal Committee
Good Laboratory Practices (GLPs)
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Applies to all research and safety studies funded or reviewed by the FDA
EPA has somewhat similar regulations
While not directly referencing surgery, these regulations vastly increase the
required amount of record keeping
Apply to FDA reviewed studies where surgical procedure, device, or compound
administration is a study component
“If it’s not recorded, it didn’t happen”
What Animals are Covered?
AWA states that protected species are all mammals (dogs, cats, NHPs, Guinea
Pig, hamster, rabbit) used for research, teaching, testing, experimentation,
exhibition purposes, or as pets.
Exclusions are birds, rats (Rattus) and mice (Mus), and farm animals not used for
research purposes
However, the Guide covers all species used as laboratory animals
 Section 4.2: US Accreditations and Guidelines
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Association for the Assessment and Accreditation of Laboratory Animal
Care (AAALAC International)
Formed in 1965
Offers an accreditation program for qualified institutions
AAALAC accreditation is not a requirement for facility operation
Standards must be maintained and verified by periodic inspections or
accreditation is lost
Uses the Guide as part of its standard for program evaluation
Guidelines for Animal Surgery in Research and Teaching (GASRT)
Required 4 years of effort
Originated with the AVMA but stalled at the issue of non-veterinarians
performing surgery
The AVMA board approved the original report up to the section on personnel and
sent the remainder to the American Society of Laboratory Animal Practitioners
(ASLAP)
Guidelines for Animal Surgery in Research and Teaching (GASRT)
ASLAP reviewed and published these guidelines in the September 1993
American Journal of Veterinary Research
Emphasized the importance of veterinary participation and oversight in animal
research while allowing surgical procedures to be performed by qualified
nonveterinary surgeons
American College of Veterinary Anesthesiologists (ACVA)
Released Suggestions for Monitoring Anesthetized Patients in 1994
Published in the Journal of the American Veterinary Medical Association
(JAVMA, Vol. 206, No. 7, 936937.)
Covers anesthetic monitoring practices and record keeping
60
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Oriented toward clinical veterinarians, however often adopted to cover research
animal anesthesia as well
Also released the guideline paper Treatment of Pain in Animals
Academy of Surgical Research (ASR)
Published as the Guidelines for Training in Surgical Research in Animals in
the Journal of Investigative Surgery (JIS, Volume 2(3):263268, 1989)
Published guidelines for surgery and surgery training on laboratory animals
Referenced in the Guide
 Section 4.3: Surgical Regulations and Guidelines
 Major and Minor Procedures:
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Major Procedure
AWA and the Guide state that any surgical intervention that penetrates and
exposes a body cavity or produces substantial impairment of physical or
physiologic functions
The Guide gives examples such as laparotomies, thoracotomies, craniotomies,
joint replacements, and limb amputations
Minor Procedure
Guide states that a procedure that does not expose a body cavity and causes little
or no physical impairment (such as wound suturing; peripheralvessel cannulation;
such routine farmanimal procedures as castration, dehorning, and repair of
prolapses; and most procedures routinely done on an "outpatient" basis in
veterinary clinical practice).
AWA does not define
 Pain and Distress
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AWA states that any procedure that could be reasonably expected to cause more
than slight or momentary pain or distress in a human is to be considered painful

Defined as in excess of that caused by minor procedures such as injections

Requires that the IACUC committee ensure that distress and pain will be
avoided or minimized

Requires veterinary consultation or guidance concerning pain relieving
drugs

Requires that any procedure that violates the above should be performed
with appropriate analgesics, anesthetics, or tranquilizers
PHS’s “U.S. Government Principals for the Utilization and Care of Vertebrate
Animals Used in Testing, Research, and Training” echoes the AWA on the use of
analgesics
Guide is less specific than the AWA

References Recognition and Alleviation of Pain and Distress in
Laboratory Animals (1992) by the Institute for Laboratory Animal
Research
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States that different species express pain and suffering in different ways so
personnel must be familiar with species specific and individual
expressions of pain

Specifies that sedatives, anxiolytics, and neuromuscular blocking agents
are not analgesics and should not be used as such
Euthanasia
AWA and PHS require that animals that suffer chronic or severe pain or distress
should be humanely euthanized at the conclusion of the procedure or, if
applicable, during the procedure
Anesthetics, Analgesics, Tranquilizers, and Paralytics
AWA

Same provisions as written for analgesics

Prohibits the use of paralytics without anesthesia
Guide

States that the choice of anesthetic agents should reflect professional
judgement

Sedatives, anxiolytics, and neuromuscular blocking agents are not
sufficient for anesthesia but may be used in combination with anesthetic
agents

Care must be taken as anesthetic depth may be difficult to assess

Recommends monitoring autonomic nervous system changes

Recommends that an appropriate level of anesthetic be defined for the
procedure without blocking agents

Guidelines for Animal Surgery in Research and Teaching (GASRT)

Discusses local, regional, and general anesthesia

Discusses types of inhalation and injectable anesthetic agents

Reaffirms the concern with improper use of muscle relaxants
Pre and Postoperative Planning and Care
AWA states that pre and postoperative care will be provided in accordance with
established veterinary and nursing procedures
Guide recommends the “team-concept” as often increasing the likelihood of a
successful surgical outcome and that a continuing and thorough assessment of
surgical outcomes should be preformed

Modification of standard techniques is allowable as long as it does not
compromise the well being of the animals

Presurgery planning should include input from all members of the surgical
team
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Identify responsible personnel
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Identify roles and needs

Identify required equipment and supplies
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Identify the facilities involved

Discuss preoperative animal healthassessment and postoperative care

Investigator and veterinarian share responsibility for postoperative care

While recovering from anesthesia, animal should be kept in a clean, dry
area and observed often by trained personnel
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During recovery, attention should be paid to body temperature,
cardiovascular and respiratory function, and signs of pain and distress

Postoperatively animals should be observed for intake and elimination,
signs of postoperative pain, infection, and the appearance of the incision(s)

Mandates good care and timely removal of staples, sutures, clips, and
bandages
Multiple Major Survival Surgery
AWA allows only if it is justified for scientific reasons by the principal
investigator in writing, is required as a routine veterinary procedure or to protect
the health or wellbeing of the animal as determined by an attending veterinarian,
or a USDA administrator determines that it fulfills appropriate special
circumstances
Guide discourages it but permits it when scientifically justified and approved by
the IACUC if:

Multiple surgeries are related components of a research project or

Will conserve animal resources or

Needed for clinical reasons

Cost savings alone is NOT an adequate reason

Requires that the IACUC should pay particular attention to the animal’s
wellbeing through continuing evaluation of outcomes

PHS policy is similar in tone
AAALAC strongly discourages it but permits it if scientifically justified and
approved by the IACUC if they are related components of a research project and
deemed essential

Cost savings alone is NOT an adequate reason
Aseptic Technique
AWA states that all survival surgery will be performed using aseptic procedures
including:

Surgical Gloves
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Masks
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Sterile Instruments

Aseptic techniques
Guide states that all major survival surgery will be performed using aseptic
procedures including:

Clipping of hair at and disinfection of the surgical site

Preparation of the surgeon

Decontaminated surgical attire

Surgical scrub

Sterile surgical gloves

Sterile Instruments, supplies, and implants

All major survival surgery will be performed using good surgical
technique including general asepsis, gentle tissue handling, minimal
dissection of tissue, appropriate use of instruments, accomplishment os
hemostasis, and correct use of suture materials and patterns
63
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Minor procedures and those involving rodents may use less stringent
measures but still require aseptic procedures and instruments
Facilities
AWA states that major non-rodent procedures must be conducted only in facilities
intended for the purpose and maintained under aseptic conditions and that minor
and rodent procedures do not require a dedicated facility but must be performed
using aseptic procedures.
Guide states that for rodents the facility may be small and simple and should be
managed to minimize contamination
Guide states that for nonrodents:

Common functional components are

Surgical support
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Animal preparation
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Surgeon’s scrub
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Operating room
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Postoperative recovery

Areas are commonly separated by physical barriers but may be achieved
with distance or timing of appropriate cleaning and disinfection between
activities

Reduce traffic and personnel

Rooms should be designed for ease of cleaning and disinfection and
appropriate ventilation

Only required equipment and supplies should be kept in the operating
room and storage minimized
 Section 4.4: Surgical Records
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USDA states that records must be maintained for the annual report and for
IACUC functions
Guide recommends maintaining the history of surgical procedures and
postoperative care, especially for dogs, cats, nonhuman primates, and farm
animals

“Reading between the lines” good record keeping is useful for the
continuing assessment of surgical outcomes
ACVA states that all drugs administered must be recorded, noting the dose, time,
and route of administration and that monitored variables (minimum of heart rate
and respiratory rate) must be recorded every 10 minutes (minimum) during
anesthesia
GLP regulations require that for surgical protocols performed under GLP
regulations, documentation must exist that shows that all parts of the protocol
were followed

i.e., if the protocol says that Ketamine will be administered IM there
should be documentation that this was done
Farm animals
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Guide states that procedures should generally follow the standard guidelines

Some minor and emergency procedures may be performed under less
stringent conditions

Still require the use of appropriate aseptic techniques, sedatives,
analgesics, anesthetics, and conditions but may not require the intensive
settings, facilities, and procedures detailed in the Guide for other animals
AAALAC recommends following the Guide

Subject to the same general ethical considerations as any other animal

Decisions should be made by the IACUC

Agricultural research should follow The Guide for the Care and Use of
Agricultural Animals in Agricultural Research and Teaching
 Part 5: Surgical Techniques
 Section 5.1: Tissue Handling
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Less tissue trauma leads to more rapid healing
Handle tissues gently and as little as possible
Retractors should be placed to avoid excessive tension
May impair blood or lymph flow which changes local physiological state
Dry tissue is dead tissue, keep it moist with irrigating saline, LRS, TisUSol, etc.
Nonessential material should be removed
Wounds with excessive debris should be thoroughly lavaged with an appropriate
sterile fluid (isotonic saline, LRS, TisUSol, etc.) to flush them away
Hemostasis
Bleeding should be stopped whenever possible
Excessive bleeding may cause hematomas or increase dead space
Hematomas prevent wound apposition and retard healing
Blood is a natural food for microorganisms and a large clot will help protect them
from the body’s immune system
Bacteria inside the clot will be protected
Bleeding may be slowed or stopped by applying pressure, clamping,
electro/thermocautery, and with various chemicals
Excessive pressure may lead to tissue necrosis
Dead Space
Dead Space is an open area in closed tissue
Filled with room air, it prevents tissue apposition, provides a space for blood and
other fluid influx, and may harbor microorganisms
 Section 5.2: Wound Healing
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Skin and fascia are the strongest tissues but regain tensile strength quite slowly
Stomach and small intestine are weak tissues, but heal quickly
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Wound Healing Phases
Phase 1 (day 0 to day 4)

Inflammatory response causes an outpouring of tissue fluids, accumulation
of cells and fibroblasts, and increased blood supply

Leukocytes produce enzymes to dissolve and remove damaged tissue
debris

Fluids flow into the wound and a scab forms

Localized edema, pain, fever, and erythema present

Basal cells migrate over the incision from the skin to cover the wound

Closure material is the primary source of tensile strength
Phase 2 (day 5 to 14)

Fibroblasts begin forming collagen fibers in the wound

Beginning of the return of tensile strength

Fibroblasts migrate toward the wound site

Begin forming collagen fibers

Tensile strength rapidly increases

Lymphatics recanalize

Blood vessels bud
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Granulation tissue forms
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Capillaries develop
Phase 3 (day 14 until done)

Sufficient collagen is now laid down to withstand normal stress

Tensile strength continues to improve for as long as one year

Skin regains 70 to 90% of its original strength

Collagen content remains constant but crosslinks with other fibers

Scar is formed which grows paler as new vessel construction tapers off

Wound contraction occurs over a period of weeks or months
 Section 5.3: Types of Wound Closure
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First Intention: Wound edges brought together during closure at the time of
surgery
Second Intention: Wound is left open and heals from the bottom up

Slower than first intention and creates more granulation and scar tissue
Third Intention: Wound is initially not closed and remains open until a
granulation bed formed, then the granulated tissue is closed using standard
techniques

Useful in infected wounds where the wound is left open until the infection
is controlled

Infected tissue should not be closed or it may dehiss

Infection is resolved naturally, or with topical and systemic treatments
 Section 5.4: Classification of Wounds
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Clean is a standard aseptic surgical wound
Clean-contaminated is a clean wound that is contaminated by entry into a viscus
resulting in minimal spillage of contents
Contaminated is a wound that has become infiltrated with contaminants from
lacerations, fractures, gross spillage from the GI tract, or a break in aseptic
technique

Within 6 hours of initial colonization a wound can be infected
Dirty-infected is caused by perforated viscera, abscesses, or a prior clinical
infection
Ongoing infection at time of surgery may lead to a 400% increase in infection
rates
 Section 5.5: Wound Closure
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Sutures
The ideal suture material:
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All-purpose, composed of material which could be used in any surgical
procedure (the only variables being size and tensile strength)

Sterile

Nonelectrolytic, noncapillary, nonallergenic, and noncarcinogenic
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Nonferromagnetic, as is the case with stainless steel sutures
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Easy to handle
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Minimally reactive in tissue and not predisposed to bacterial growth
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Capable of holding securely when knotted without fraying or cutting
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Resistant to shrinking in tissues
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Absorbed with minimal tissue reaction after serving its purpose
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Doesn’t exist!
Surgeon should select suture materials for:
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High uniform tensile strength (quality)
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Permitting use of finer sizes
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Suture should be the smallest diameter that will do the job
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Consistent uniform diameter
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Sterility
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Pliable for ease of handling and knot security
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Freedom from irritating substances or impurities for optimum tissue
acceptance
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Predictable performance
Size
Generally stated in “oughts”; i.e., 3-0, 5-0, etc.
2-0 is larger than 4-0, 0 is larger than 2-0, etc.
Some suture and wire is larger than 0, then numbered 1 and higher
2 is larger than 1, 6 is larger than 1, etc.
From smallest to largest:
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7-0, 3-0, 0, 1, 3, 7, etc.
Monofilament suture:
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Is a single strand
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Passes through tissue easily, won’t harbor microorganisms
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Ties easily
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May be weakened by crushing (clamping in forceps or needle holders)
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Has more “memory”
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Continues to hold the shape as it lay in the package
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Good for percutaneous sutures as the smooth surface is less prone to
drawing microorganisms into the tissue
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Knots may slip over time due to the comparative slipperiness of the suture
Multifilament suture:
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Is a bundle of strands, like rope
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Affords greater tensile strength, pliability, flexibility, and knot security
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May harbor microorganisms and “wick” them down the suture
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Should not be used for percutaneous sutures
Absorbable suture maintains strength temporarily but gradually loses tensile
strength and is eventually mostly or completely absorbed
Nonabsorbable suture will retain tensile strength and not be absorbed
Many nonabsorbable sutures (silk) will lose some tensile strength over time
Useful for device fixation, areas of extreme tension, slow healing areas, or
percutaneous skin sutures
Selected for procedures where the suture should be permanent
Surgeon’s Knot
An initial double throw followed by one or two single throws is generally
sufficient
Extra throws do not add appreciable strength to the knot and may, in fact, weaken
it while adding extra bulk
The exception is nylon monofilament sutures, where two successive double
throws are useful to prevent slippage
 Section 5.6: Suture Patterns
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Simple Interrupted
Maintains strength and tissue position if one portion fails
Requires more time and suture material
Has minimal holding power against stress
Horizontal Mattress
Tension suture
Useful in skin of dog, cow, and horse
Rapid and involves less suture material
Difficult to apply without excessive eversion
Should pass just below the dermis
Tightness should be such that the skin edges just meet
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Vertical Mattress
Tension suture
Stronger than the horizontal mattress
Time consuming and requires more suture material
Cross-mattress
Tension suture
Brings tissue into good apposition
Useful in suturing stumps (amputations)
Also useful for rib apposition and abdominal muscle closure
Gambee or Crushing
Useful in intestinal anastamoses
Permits minimal leakage
May reduce fluid passage through the lumen underneath
Crushing is similar to a vertical mattress pattern
Simple Continuous
Usually used for lines no longer than 5”
Involves one diagonal pass and one perpendicular pass
Provide minimal tension holding but hold tissue together in good apposition
Creates a good seal
More prone to failure if any portion is broken
Running
Both deep and shallow passes advance
Regularity more difficult
Slightly faster than a simple continuous pattern
Weaker than a simple continuous pattern
Ford Interlocking
More stable in the event of partial failure or breakage
Provides greater tissue stability
Uses more suture material
Lembert
Closes hollow viscera
Provides inversion and creates a good fluidtight seal
Halsted
Combination mattress and Lembert pattern
Connell
Begun with a single inverting vertical mattress suture
Continues for the length of the incision
Cushing
Modified Connell where the needle and suture do not enter the lumen
Provides a better fluidtight seal than the Connell pattern
Parker-Kerr
A single layer of Cushing covered by a single layer of Lembert
Used for infected uterine stumps and some bowel closures
Provides complete clamping to prevent leakage during suturing
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Rochester-Carmalt forceps are used to clamp the lumen shut and then slowly
withdrawn while placed suture is tightened to prevent spillage of contents
Guard
Modified Cushing
Closes incisions of the rumen, intestine, and uterus
Needle does not enter the lumen
Starts slightly higher than start of incision
Inverting pattern
Continuing Everting Mattress
Provides increased strength
Rapid placement
Subcuticular
Does not penetrate the surface of the skin
Rapid and uses little suture material
Used to close the uppermost layer of the skin incision
Requires no suture removal
Subcutaneous
May use simple interrupted, simple continuous, or horizontal mattress
Simple continuous is fast and eliminates dead space
Quilted
Exteriorized skin suture through plastic tubing to resist excessive tension and
stress
Useful for high-tension closures
Far-far, Near-near
Tension pattern
Overlapping suture pattern provides extra strength but requires extra suture
material
Near-far, Far-near
Tension pattern
Overlapping suture pattern provides extra strength but requires extra suture
material
Mayo Mattress
Useful for midline abdominal closures, abdominal hernia repair, and secondary
cleft palate repair
Bunnell
Used for apposing tendons
Requires a high degree of closure strength
Uses nonabsorbable suture
Uses a doublearmed suture
Modified Bunnell
Used for apposing tendons
Requires a high degree of closure strength
Uses nonabsorbable suture
Uses a singlearmed suture
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Cerclage Wiring
Used for fracture repair
Wire/pin placed in the bone center to hold it together
Wire winds about the bone under the periosteum
Hemicerclage
Wire goes through holes drilled in the bone
Suture Patterns for Specific Tissues
Skin: simple interrupted, horizontal mattress, vertical mattress, continuous
apposing or everting
Subcutaneous tissue: simple continuous
Fascia simple continuous (primary), simple interrupted, vertical mattress, farnear,
nearfar, Mayo mattress
Peritoneum: simple continuous (two layers), and simple interrupted
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Very thin and fragile in horse, close muscle instead
Vessels: simple interrupted and simple continuous
Viscera: direct appositional Cushing suture
Muscle: simple continuous, simple interrupted, and horizontal mattress
Tendons: Bunnell
Bone: hemicerclage and cerclage
 Part 6: Basic Anatomy and Physiology
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Functional Organ Systems
Skin
Muscular
Connective Tissue
Skeletal
Cardiovascular
Respiratory
Gastrointestinal
Nervous
Filtration and Excretory
Lymphatic
Sensory
Reproductive
Endocrine

Covers the body and connects to the mucous membranes of the digestive,
respiratory, and urogenital tracts as well as the conjunctivae of the eyelids, the
lacrimal duct, and the typanic membrane
Acts as a physical barrier between the environment and underlying tissues
Assists in regulation of temperature and hydration as well as sensation
Consists of the epidermis, dermis, and a subcutaneous layer of adipose tissue
 Skin
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Consists of connective tissue bed containing blood vessels, lymphatics, muscles,
and nerve endings covered by a stratified squamous epithelium
 Muscles
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Three types:
Smooth found in the walls of hollow organs and in blood vessels and is under the
control of the autonomous nervous system
No striations
Cannot be voluntarily controlled
Spindle shaped and without striations
Makes up almost all visceral muscle except cardiac muscle
Lines the interior of blood vessels
Used for slow, steady contractions
Involved in the movement of food and waste products in the GI tract and bladder
Involved in vasoconstriction
Organized into sheets of fibers surrounded with endomysium and connected by
strands of collagen and elastin
Cardiac forms the bulk of the heart and is optimized for rhythmic contractions
under the control of the autonomic nervous system (ANS)
Found only in the heart
Striated (but shorter than skeletal)
Cannot be voluntarily controlled
Works in steady, rhythmic fashion
Controlled by the heart’s pacemaker
Short and branched
Surrounded by endomysium and connected by intercalated discs
Skeletal forms bundles surrounded by connective tissue envelopes largely
controlled by the somatic nervous system (SNS)
Longest muscle cell types
Striated
Can be voluntarily controlled
Made of hundreds to thousands of individual muscle cells called fibers
Muscle fibers are enclosed in connective tissue called endomysium
Fibers are gathered into bundles called fascicles bound by perimysium
Fascicles are bound together by epimysium
Origin is the more fixed point of muscle attachment
Insertion is the more movable point of muscle attachment
In limbs, the insertion is always distal to the origin
Movement types
Extensor opens a joint or straightens the bone alignment
Flexor closes a joint or angulates the bones
Adduction moves the extremity toward the median plane (MP)
Abduction moves the extremity away from the MP or the axis of the limb
Circumduction moves an extremity in a plane represented by a cone
Rotation moves a part along its long axis
72
 Connective tissue:
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Provide routes for nerves and blood vessels
Envelope, separate, or connect muscles, nerves and blood and lymphatic vessels
May blend with the periosteum of bone
Periosteum connective tissue covering bone
Perichondrium connective tissue covering cartilage
Peritoneum a serous membrane largely made of connective tissue
Parietal peritoneum covers the abdominal, pelvic, and scrotal cavities
Visceral peritoneum covers the abdominal, pelvic, and scrotal organs
Connecting peritoneum connects organs to other organs or the parietal
peritoneum
Common dorsal mesentery peritoneal fold which incorporates most of the
abdominal organs
Pericardium fibrous sac that envelopes the heart
Mediastinum fibrous sheet that separates the two sides of the thoracic cavity and
incorporates the heart, thymus, vena cava, and aorta
Pleurae serous membranes that line the thoracic cavity and cover the lungs
Meninges Protective membranes covering the brain and spinal column
Dura mater thick, fibrous, and the most superficial of the meninges
Arachnoid membrane delicate and lines the deep surface of the dura mater
Pia mater delicate and coats the surface of the brain, spinal cord, nerve roots, and
the optic nerve
 Skeleton:
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“The framework that the body hangs on”
Supports and protects the body
Provides attachment points for the muscles and acts as levers for motion
Made up of individual bones connected by ligaments and muscles
Bones
Two types of bone tissue
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Compact bone: Dense tissue that forms the outer shell of all bones
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Spongy bone: Filled with pockets and lays in between most compact bone
surfaces
Types of bones
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Long bone consists of a shaft (diaphysis) with two extremities (proximal
and distal epiphysis)
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Includes all bones in the limbs except the patella and those of the wrist
and ankle
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Short bone is roughly cubelike, primarily spongy bone surrounded by a
thin layer of compact bone
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Bones of the wrist and ankle
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Sesamoid bone is a short bone embedded in a tendon or joint capsule
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i.e., the patella
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Flat bone is a thin bone with spongy bone called diploe encased in
compact bone
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The sternum, the ribs, and most bones of the skull
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Irregular bone – bones that don’t fit into the previous categories
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Vertebrae, pelvis, some skull bones
Structure of a flat bone, outside to inside
Periosteum, a fibrous tissue connected to the bone by Sharpey’s fibers
Compact bone
Spongy bone which contains either red bone marrow or a medullary cavity
(containing yellow bone marrow)
The medullary cavity in spongy bone as well as the internal termination of the
compact bone is lined with a fibrous tissue called endosteum
General Information
Bone acts as a storage site for calcium and phosphorus
Bone components produce both red and several types of white blood cells
The skull is made of the incisive, nasal, maxilla, zygomatic, lacrimal, frontal,
palatine, pterygoid, sphenoid, parietal, occipital and temporal bones
Occipital bone has sagittal and nuchal crests
Radius and tibia are the main weight supporters of the lower limbs
Consists of ~321 bones in the dog
50 separate bones for the skull and hyoid
50 vertebrae
7 sternum and the xiphoid process
26 ribs
90 bones in the forelimbs
96 bones in the hindlimbs
1 Os penis in the male
Joints are where bones are joined by fibrous, elastic, and/or cartilaginous tissue
Ligament – fibrous tissue connecting bone to bone
Tendon – fibrous tissue connecting muscle to bone
May be categorized by functionality or structure
Function
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Synarthroses – permits no movement
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Amphiarthroses – permits slight movement
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Diarthroses – permits free movement
Structure
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Fibrous bones are joined by fibrous tissue, no joint cavity exists (skull
sutures, teeth) and provide little or no movement
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Cartilaginous bones are united by cartilage, no joint cavity exists
(Epiphyseal disc, intervertebral disc), and permits compression or
stretching
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Synovial bones are separated by a joint cavity and permits significant
movement
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Synovial joints may be plane, ball-and-socket, ellipsoidal, hinge, condylar,
trochoid, or saddle joints
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5 main components of synovial joints:
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Articular cartilage covering the bone at the joint
Has limited regeneration capabilities
Articular capsule encloses the joint in an outer fibrous capsule and an
inner synovial membrane
Hip and knee joints have a fatty pad between the fibrous capsule and the
synovial membrane or bone
Joint cavity is the potential space within the articular capsule that is filled
with a nutrient and waste transporting fluid called synovial fluid
Synovial fluid is a lubricant made of hyaluronic acid thinned by interstitial
fluid from blood plasma
Reinforcing ligaments reinforce and strengthen the joint (intrinsic,
extracapsular, intracapsular)
 Nervous System
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Brain
Composed of cerebrum, cerebellum, and brain stem
Cerebrum primary site of cognitive and sensory functions
Cerebellum coordinates movement and posture
Brain stem source of all cranial nerves except the olfactory nerves and is
continuous with the spinal cord
Divided into two systems; central nervous system (CNS) and peripheral nervous
system (PNS)
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In reality it is a single integrated system which science has arbitrarily
divided
CNS consists of the brain and spinal cord
Processes sensory information and sends commands
PNS is everything else
Sensory (afferent) division conveys impulses from sensory organs to the CNS
Motor (efferent) division transmits impulses from the CNS to muscles and glands
Efferent Division
Divided into two systems
Somatic Nervous System (SNS) conducts impulses to muscle fibers and allows
voluntary control
Autonomic Nervous System (ANS) regulates smooth muscles, cardiac muscles,
and glands
ANS divided into two systems;
Sympathetic Division
Originates from the spinal cord between T1 and L2
Parasympathetic Division
Originates from the brain stem and sacral region of the spinal cord
Sympathetic and parasympathetic regulate each other
Brain floats in cerebrospinal fluid
Contains inorganic ions, protein, sugar, and a few misc.cells
Derived from blood and returns to blood stream via arachnoid villi and lymphatics
Spinal cord
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Extends from the brain stem through the vertebral canal
Conducts signals to and from the brain
Acts as a reflex generator
Processes information and discharges commands
Has a central canal that carries cerebrospinal fluid
Neurons
Have a body (soma) that contains the nucleus and cytoplasm
Dendrites are small branches extending from the soma that act as receptive sites
to conduct electrical signals toward the soma
The axon stems from the soma and transmits nerve impulses away from the soma
to axonal terminals
Axonal terminals conduct signals to muscles, glands, and other nerves
Nerves
A nerve fiber (neuron) is surrounded by fibrous tissue called endoneurium
Nerve fibers are bound into bundles with perineurium to form fascicles
Fascicles and blood vessels are bound into nerves by epineurium
In the CNS nerves are termed tracts
Nerves are highly variable in structure and may differ from these descriptions
 Cardiovascular System:
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Heart
Made up of 4 chambers
Deoxygenated blood enters the right atrium via the vena cava
Blood is then pumped through the right atrio-ventricular valve (a tricuspid valve
although it consists basically of two cusps) into the right ventricle
Blood is then pumped through the pulmonary valve into the pulmonary artery, to
the lungs for oxygenation, back through the pulmonary veins, and into the left
atrium
Blood is pumped through the left atrio-ventricular (bicuspid or mitral) valve into
the left ventricle
Blood is pumped to the aorta and then throughout the body
Heart is kept supplied with blood via the right and left coronary arteries which
divide into the various branches (right marginal branch, circumflex branch, left
marginal branch, etc.) that supply the heart
Acts as the primary pump of the cardiovascular system
Contraction involves the Sinoatrial (SA) Node, Atrioventricular (AV) Node, AV
Bundle (Bundle of His), right and left branches, and Purkinje fibers
SA Node is a pacemaker that depolarizes in a sinus rhythm to begin the
contraction of the atria and conducts the signal via the atria to the AV Node
AV Node delays the impulse to allow the atria to fully contract and then transmits
the signal
AV Bundle transmits the signal to the branches which then transmit it to the
Bundle of His which is made up of Purkinje fibers
Purkinje fibers transmit the signal evenly throughout the ventricles to ensure even
contraction in a wringing manner towards the atria
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Contraction does not require outside stimuli but can be regulated by the ANS
Cardiac Cycle
Systole is the contraction period of the heart
Diastole is the resting period
Mid to late diastole involves low blood pressure in the heart and blood passively
flowing through the atria into the ventricles
AV valves are open
Atrial Systole involves the atria contracting
Ventricular Systole starts as the atria go into diastole and involves ventricular
contraction
Momentarily all valves are closed and ventricular pressure rises sharply
Early Diastole is where the ventricles begin to relax
Cardiac Output
Amount of blood pumped out by each ventricle in 1 minute
Heart Rate times Stroke Volume
Stroke Volume is the volume of blood pumped by the left ventricle for each
contraction
Heart Sounds
“Lupdub” sound results from the valves closing
“Lup” is AV valve closure
“Dub” is the semilunar valves closing
Unusual sounds are termed murmurs
Vascular System
Distribution of blood
The bulk (70%) of the blood is in the venous system with only 10% in the arterial
system
Blood leaves the heart via the aorta and cardiac arteries
Arteries carry blood to smaller arterioles
Arterioles carry blood to capillaries
Oxygen is supplied to the tissues around the capillaries
Capillaries return deoxygenated blood to venuoles
Venuoles carry blood to veins
Veins carry blood to the vena cava
The vena cava returns blood to the heart
Arteries and Veins
Tunica Intima is the inner surface of the vessel consisting of a single layer of
endothelium with a basement membrane
Tunica Media is made of smooth muscle and elastic fibers
Layer is much thicker and stronger in arteries
Tunica Adventitia is made of collagen fibers
Capillaries
Made of endothelial cells and a sparse basal intima
Primary site of oxygen exchange between the blood and body tissue
Aorta
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Carries all oxygenated blood from the heart
Extends cranially before making a 180 degree halfcircle to proceed caudally
Arbitrarily divided into the ascending aorta, aortic arch, descending aorta
(thoracic and abdominal aorta)
Arteries
Originate from the aorta
Main surgical arteries are:
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Brachiocephalic trunk: Originates at aortic arch and feeds both common
carotid arteries and the right subclavian artery
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Left and right common carotid arteries: Originate at the brachiocephalic
trunk and branch to become the internal and external carotid arteries at
C1C2
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Left subclavian artery: Originates at the aortic arch
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Right subclavian artery: Originates at the brachiocephalic trunk
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Subclavian arteries continue as the axial arteries which feed the forelimbs
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Axial arteries: Continue as the left and right brachial arteries which feed
the forelimb
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Celiac artery: Originates at the abdominal aorta and branches into the
hepatic, gastric, and splenic arteries
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Cranial and caudal mesenteric: Originate at the abdominal aorta and feed
the intestines
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Left and Right renal arteries: Originate at the abdominal aorta and feed the
kidneys
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Left and right external iliac arteries: Branch from the termination of the
abdominal aorta and continue as the left and right femoral arteries
Veins
Return deoxygenated blood from the capillary beds to the heart
Main surgical veins are:
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Left and right femoral veins: Transport blood in the hindlimbs to the
external iliac vein
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Left and right external iliac veins: Continue the femoral veins and join the
common iliac when joined by the internal iliac vein

Common iliac veins: Connects to the caudal vena cava
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Portal vein: Collects blood from pancreas, spleen, and all of the GI tract
save the anal canal and connects to the liver and thence to the hepatic
veins that connect to the caudal vena cava
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Left and right external jugular: Continues the internal and external
maxillary veins and connects to the brachiocephalic veins
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Cephalic vein: Connect to the brachiocephalic vein and provide flow from
the forelimbs and is situated on the lateral aspect of the forelimb
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Brachial vein: Connecst to the brachiocephalic vein and provide flow from
the forelimbs and is situated on medial aspect of the forelimb
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Left and right subclavian veins: Drain into the cranial vena cava
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Vena Cava: Collects venous blood and drains into the right atrium and is
arbitrarily divided into cranial and caudal vena cava at the diaphragm
before it drains into the heart
 Respiratory System:
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Transports oxygen from the outside environment to the blood stream
Parts of the respiratory system
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Pharynx: The main passageway from the nose and mouth

Larynx: Musculocartilaginous organ that protects the entry to the trachea
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Parts of the respiratory system

Trachea: Flexible, wall of smooth muscle surrounded by Cshaped rings of
hyaline cartilage
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Passageway for air to the left and right principal bronchus
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Bronchus: Divides into lobar bronchi which then divide into segmental
bronchi which further divided into the alveoli
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Lung: Organ containing the bronchus, bronchi, and alveoli

Are passive organs, inflation being due to the diaphragm
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Each lung lies in an essentially potential cavity called the pleural
cavity
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Is a thin film of moistening fluid
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Becomes a true cavity in a pneumothorax
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Left is slightly smaller than the right due to the heart’s position
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Made up of highly vascularized tisse filled with alveoli
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May be visualized as a collection of millions of tiny bubbles
surrounded with elastic connective tissue (stroma)
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Alveoli: Site of oxygen transfer to the blood
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Diaphragm: Muscular wall that separates the thoracic and abdominal
cavities and creates negative pressure in the thoracic cavity to inflate the
lungs
 Gastrointestinal System:
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Pharynx: Passageway from the mouth to the Esophagus
Esophagus: Passageway from the pharynx to the stomach
Stomach: Site of storage and mixing of food and adds digestive enzymes
Small Intestine:
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Duodenum: First and most fixed portion of the small intestine as it leaves
the stomach
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Jejunum: Next portion of the small intestine
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Ileum: Last portion of the small intestine and connects to the ascending
colon portion of the large intestine
Large Intestine
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Cecum: Does NOT connect the ileum and large intestine and is a
diverticulum of the colon
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Colon: Connects to the rectum
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Rectum: Connects to the anal canal which exits the body
 Filtration and Excretory System
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Eliminates waste products from the body
Liver
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Largest gland in the body
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Produces bile
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Stored in the gall bladder
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Releases endocrine substances into the bloodstream to assist in the
metabolism of fats and sugars
Gall bladder: Stores and concentrates bile
Pancreas: Secretes pancreatic juice for digestion, produces insulin in its islet cells,
and has two lobes
Kidney: Primary filter for blood and produces urine which is carried by ureters to
the bladder
Bladder: Stores urine prior to urination and excretes urine via the urethra
 Lymphatic System:
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Returns fluid and protein lost from blood in the capillary beds
Lymph nodes, spleen, thymus, and the tonsils are phagocytic and extract foreign
bodies
Produce and circulate cells that are responsible for the bodies immune response
Thymus: Located cranial-ventrally from the heart
Spleen: Lays parallel to the greater curvature of the stomach
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Eye: Responsible for vision
Ear: Responsible for hearing
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Male genital organs
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Scrotum: Skin pouch that encloses a testis
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Testes: Male gonads that produces spermatozoa
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Prostate gland: Accessory sex gland
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Penis: Composed of the roots, body, and glans
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Os penis: 10 cm long bone in the glans penis of the dog
Female genital organs
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Ovaries: Paired organs that produce ova
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Uterine tube: Transports ova to the uterus
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Uterus: Conducts sperm to the uterine tube and consists of a neck and two
horns
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Vagina: Dilatable canal from the uterus to the vulva
 Sensory Specific Organs
 Reproductive System:
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 Part 7: Surgical Instruments
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The purpose of this module is to illustrate the most common instruments and give
some recommendations for their use
It should be noted that individual surgeons may use instruments in nonstandard
ways
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This is acceptable so long as the animal and procedure are not compromised
Forceps
 Typically, forceps that require squeezing are used on tissue and those with finger
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rings and locking mechanisms are used on nonliving tissues
Adson Forceps
Have three teeth
Useful for gripping tissue
Adson-Brown Forceps
Used for gripping tissue
Less traumatic to tissue than non-toothed forceps
Requires less crushing pressure to maintain a grip than non-toothed forceps which
leads to less vascular damage
Mayo (Russian) Forceps
Useful for gripping delicate tissue
Thumb forceps
General purpose tissue gripping forceps
Should not be used for “slippery” tissues since excessive gripping pressure will
cause vascular damage
Tuttle thoracic tissue forceps
Used for gripping delicate and “slippery” tissues
Ringtip distributes the pressure on the tissue
Lack of teeth prevents punctures into vessels or lung tissue
Singley tissue forceps
Used similarly to Tuttle thoracic tissue forceps in the abdomen
Prevents punctures into the GI tract
Debakey thoracic forceps
Large number of teeth distributes the pressure to help avoid punctures
Cushing neuro tissue forceps
Delicate tipped forceps for gripping AROUND nerves
Not used for gripping the actual nerve
Jewelers forceps
Used for delicate gripping
Does not grip tightly
Babcock tissue forceps
Used for atraumatic tissue holding of tissues that cannot be perforated, such as the
intestines
Allis tissue forceps
Teeth tightly grip soft tissue
Chester and Ballenger sponge forceps
Hold gauze sponges for applications in body cavities
Crille hemostatic forceps
Have grooves running from tip to hinge
This allows less slippage when tension is applied perpendicularly to the jaws
Kelly hemostatic forceps
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Have grooves running side to side of the jaws
This allows less slippage when tension is applied parallel to the jaws
Mosquito hemostatic forceps
Similar to but with smaller jaws than Kelly forceps
Useful for gripping small bleeding vessels
Hartman mosquito hemostatic forceps
Smaller versions of Mosquito forceps
Mixter thoracic forceps
Kelly-style forceps with a sharp angle towards the tip of the jaws
Useful for gripping bleeding vessels at an angle
Useful for positioning ligatures around vessels
Collin gallbladder forceps
Relatively atraumatic forceps used for retraction and gripping of the gall bladder
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Backhaus towel forceps
Used for clamping sterile drapes or towels together when creating a sterile field
May also be used to clamp sterile drapes directly to the skin
Roeder towel forceps
Have ball-stops to prevent towel slippage up the pins
Edna towel forceps
Grip towels without puncturing them due to flat pins
Must not be used on skin due to crush damage
Jones cross-action towel forceps
A variation on Backhaus towel forceps
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Mayo dissecting scissors
Used for dissection of tissue
Often used for cutting sutures and sterile paper drapes
Operating scissors
Used for cutting suture and sterile paper drapes
Metzenbaum dissecting scissors
The primary scissors used for tissue dissection
Also useful for cutting tissue
Strabimus (“baby metzenbaums”)
Used for fine dissection of tissue
Stevens Tenotomy scissors
Designed for cutting or dissection of a tendons and often used for fine dissection
in other tissues
Iris scissors
Designed for fine dissection in the eye
Often used for very fine dissection and creation of phlebotomies and arteriotomies
Wire scissors
Used for cutting orthopedic and approximation wire
 Towel Clamps
 Scissors
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Lister bandage scissors
Used for cutting bandage material
Flared tip prevents catching tissue
Weck Spencer suture scissors
Have a cutout semicircle in the lower blade tip to allow it to slip under a tight
suture
 Needle Holders
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Mayo Hegar needle holder
Holds a suture needle for wound closure
Olsen Hegar needle holder
Contains scissor blades to allow easy suture cutting
Finochietto and Debakey thoracic needle holders
Have specialized tips and/or mechanisms to allow easier deep tissue suturing
Castroviejo micro needle holder
Used for delicate suturing and holding very small suture needles
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Gelpi retractors
Used for holding open incisions for better visibility
Weitlaner retractors
Used for tissue retraction with a more distributed opening of that tissue than with
Gelpi retractors
Senn retractor
Used for manual tissue retraction
Bernay finger rake retractors
Used for manual retraction of tissue
Volkmann rake retractors
Similar to Bernay retractors with a larger handle for improved handling
Ochsner ribbon retractor (malleable)
Highly bendable strip of metal that allows bending into whatever configuration
will allow the best retraction
Primarily used for abdominal retraction
Parker retractors
Nonflexible retractors
Commonly used for abdominal retraction
Deaver Retractors
Used for abdominal retraction
Mayo abdominal retractor
Used for abdominal retraction
O’Sullivan, O’Connor and Wexler abdominal ring retractors
Used for holding multiple abdominal retraction paddles for handsfree retraction
Love nerve retractor
Used for holding individual nerves or fibers
Balfour retractors
Used for thoracic retraction
 Retractors
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Finochietto rib spreader
Used for spreading ribs for thoracic access
Bailey rib approximator
Used for bringing ribs together for closure following a thoracic procedure
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Cooley cardiovascular clamps
Used for isolating sections of major vessels
Partial clamping will isolate sections while allowing blood flow around the
clamped section
Renal clamps
Used for clamping renal vessels
Serrefines (bulldog) vascular clamp
Used for clamping superficial vessels
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Yankauer suction tube
Used for suctioning fluids out of the surgical field
Debakey suction tube
Another style of suction tip
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Periosteal elevators
Used for retraction of the periosteum
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Lebsche sternum knife, mallet, Stille-Liston bone cutting forceps
Used for cutting or splitting bone during orthopedic procedures
Pilling-Ruskin, Beyer, and Jansen-Zaufel rongeurs
Used for “chipping” off small pieces of bone
Bruns bone and Spratt mastoid curettes
Used for scraping and carving bone
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Emesis basin
Designed for collecting vomit
Often used for holding damp sterile sponges
Sponge bowl
Used for holding sponges and sterile fluids
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Silverman style
Used for collecting tissue samples
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Used for absorption of fluids in a surgical field
 Clamps
 Suction Tubes
 Elevators
 Orthopedic
 Bowls
 Biopsy Needles
 Sponges
 Part 8: Sterilants, Disinfectants, and Antiseptics
84
 Section 8.1: General
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Sterilization: The physical or chemical destruction of all microbial life including
highly resistant bacterial spores
Disinfection: The inactivation of most pathogenic organisms except for some
highly resistant forms (spores) on inanimate surfaces and implies the destruction
of the vegetative forms of bacteria but not spores
Antiseptic: A substance that inhibits or destroys microorganisms on or in living
tissue
Asepsis: A state of freedom from infection
Aseptic technique: The steps required to prevent contamination of the surgical site
with infectious agents
 Methods of sterilization
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Filtration
May be used for gasses or liquids
Involves the separation of particulate matter of known sizes using a membrane
Commonly used for pharmaceutical liquids
Useful for heat sensitive media, offers high through-put, and provides absolute
sterilization
Unable to differentiate between similarly sized particles
Radiation
Usually gamma radiation from Cobalt60
Provides penetration through relatively impervious materials (i.e., metal and
plastic)
Leaves no chemical residue
Can start a structural change in materials, especially some polymers, that may
continue to develop over months
Usually used by manufacturers due to cost of the process
Thermal
Most common form of surgical sterilization
Believed to denature bacterial proteins
Sterilization is a function of time and temperature
Two types, dry and wet
Dry heat (i.e. hotbead sterilizer) used on moisture sensitive materials such as oils,
powders, and petroleum products
Causes protein oxidation which requires longer exposure or higher temperatures
Wet heat (boiling water and autoclave) kills bacteria via the coagulation of critical
proteins
Boiling water
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A poor sterilant at ambient pressure
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Has a relatively low temperature
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May be enhanced by the addition of sodium hydroxide or sodium
carbonate
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Destructive to instruments, especially glassware and rubber
Autoclave
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Involves superheated steam under pressure to allow higher temperatures
than normal steam can provide
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Requires materials and wrapping that are not damaged by heat, moisture,
and pressure and are permeable to the steam.
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Requires complete saturation of the surgical pack for effective sterilization
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i.e., 121 degrees C for 13-15 minutes (5-10 minutes plus 3-8 minutes as a
safety margin)
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Larger or denser packs require more time for adequate saturation with
steam
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Time for the autoclave to reach temperature and saturate the pack is the
heat-up time
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Prevacuum autoclaves achieve this heat-up time in 12 minutes
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Can be used for emergency “flash” autoclaving
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Also reach higher temperatures and so require shorter exposure times (131
degrees C for 3 minutes)
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Loads should be vented for ~10 minutes following a cycle to prevent
condensation
Liquid Chemical
Important to differentiate between sterilants and disinfectants
Sterilants are designed to kill all microorganisms, disinfectants are not
Disinfectants are NOT adequate for instrument and implant/catheter sterilization
Chemical sterilants are regulated by the FDA as medical devices

EPA involved as well
Approved chemical sterilants will say on the bottle that they are sterilants
Nonsterilant chemicals will have disinfectant written on the bottle and should not
be used for instrument or device sterilization
Cold sterilants work by contact, care should be taken that all surfaces are in
contact with the solution
Flush sterilant through catheters, open all latches, etc.
Cold sterilants are tissue irritants and require complete rinsing (sterile water or
saline) of sterilized objects to remove all chemicals prior to tissue contact
Aldehydes
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Glutaraldehyde
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Requires >12 hours of full immersion for sterilization of resistant spores
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Noncorrosive
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Activated solutions have less than 2 week shelf life
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Toxic to skin, eyes, respiratory tract
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Glutaraldehyde solutions come in different strengths

Only those classed as a sterilant should be used for instrument or device
sterilization
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Formalin
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37% aqueous formaldehyde
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Requires >24 hours of full immersion for sterilization of resistant spores
Toxic to skin, eyes, respiratory tract
Hydrogen Peroxide
6% aqueous solution with >30 minute exposure may kill some resistant
spores in addition to less hardy microorganisms
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Potentially explosive at high concentrations
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Corrosive
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Irritant to skin and eyes
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Peracetic acid (35%)
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Steris System 1
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Automated process suitable for endoscopic equipment
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Fast (3045 minutes) and has environmentally friendly byproducts
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Useful only for small loads of instruments and provides no sterile
packaging, must be used immediately upon cycle completion
Gas Chemical
Requires an enclosed chamber similar to an autoclave
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Ethylene Oxide (ETO)
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Colorless gas
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Flammable, explosive, toxic, and irritating to skin and mucus membranes

Destroys metabolic pathways by alkylation

Typically requires 12 hours of exposure

Time is inversely proportional to pressure

Requires ~24 hours of ventilation after cycle

Hydrogen Peroxide
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Safer than ETO to the user
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Requires little ventilation and shorter exposure times
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Cannot be used with absorbent materials such as paper or cloth

Will condense into water and soak the packaging, preventing gas contact
and allowing poststerilization “wicking” of microorganisms through the
packaging
 Section 8.2: Sterilization Procedures
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All instruments must be thoroughly cleaned prior to sterilization
Organic debris can dramatically extend the required time for sterilization
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i.e. Glutaraldehyde sterilization time increases from 12 hours to 48 hours
in the presence of organic debris
For most forms of sterilization instruments should be dry
Not as important for steam autoclaving
Some residual moisture is important for ETO sterilization
Sterilization indicators should be used to verify proper sterilization of items
Sterilization sleeves have indicators on them
Packs should use indicators inside the inner wrap and under or inside any
containers or large objects
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Instruments should be open and accessible to steam or gas
Open instruments allow steam or gas access to hinges and clasps
Upside down bowl filled with gauze may not allow steam or gas to penetrate,
leaving unsterilized items in the pack
Items should be placed so as to not puncture the wraps or sleeves
Packs and sleeves should be dated on the day that sterilization is completed
Paper/plastic wrapped items/packs are typically sterile for 6 months when stored
in closed cabinets
Cloth wrapped items are considered sterile for 8 weeks when stored in closed
cabinets
Packs and sleeves that get wet or are punctured should be considered nonsterile
If there is any doubt about sterility, consider it nonsterile
Steps for Wrapping Packs

Step 1: Lay Instruments on tray and place on two paper or cloth drapes

Step 2: Fold corner of first drape tightly over the instruments, fold back to
prevent overlap
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Step 3: Fold the side corners of the first drape tightly over the instruments,
fold back to prevent overlap
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Step 4: Fold opposite corner of first drape over and tuck into the space
created by the other three folds
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Step 5: Pack should be tightly wrapped with the first drape
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Step 6: Repeat steps 15 with the second drape, working from the opposite
side
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Step 7: Tape the 2nd drape with indicator tape and label with contents and
date of sterilization
 Section 8.3: Disinfection
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Primarily chemical
High-level disinfectants used for instrument disinfection between rodent
procedures, some oral procedures, and for delicate endoscopic equipment that
cannot be sterilized
Intermediate and some low-level disinfectants should be used for cleaning
surfaces in surgery
Disinfectants rated as high, intermediate, or low based on efficacy against
microorganisms
 High-level Disinfectants
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Used for instrument disinfection between rodent procedures and for critical
surface cleaning
Aqueous Iodine
Contains higher levels of free iodine
Cytotoxic
Stains surfaces
30 minutes of exposure for disinfection
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Aldehydes
30-45 minutes of exposure for disinfection
Sodium hypochlorite (bleach)
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Toxic
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Corrosive
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3,000 ppm for 45-60 minutes for disinfection
Phenol compounds (carbolic acid)
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No longer commonly used
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30 minutes for disinfection
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Intermediate-level Disinfectants

Used for cleaning surfaces
Iodophor (Povidone iodine)

Iodine complexed with surfactants or polymers for slower release of free
iodine

Dilution lowers cytotoxicity and increases bactericidal activity

Rapidly deactivated in the presence of organic matter
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Residual activity of 46 hours
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May be mildly irritating
Chlorhexidine
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Rapid onset and long residual activity (8-12 hours)
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Not deactivated by organic matter
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Nonirritating
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Considered superior to Iodophors due to residual action even when dried
 Low-level Disinfectants:
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Alcohols (Isopropyl)
Bactericidal
Ineffective against most spores and fungi
Minimal residual effects and inhibited by organic debris
Cytotoxic
Degreaser
30 minutes exposure for surface decontamination
Quaternary Ammonium (Quat, Zephiran)
Bactericidal
Work by dissolving outer coatings on some pathogens
Some bacteria, including Staphylococcus aureus and Pseudomonas, have
common resistant strains
Ineffective against spores and some viruses
May support growth of some types of bacteria
Per CDC, is not an appropriate sterilant
Low toxicity in stable solutions
10-30 minutes for surface decontamination
 Antiseptics:
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Commonly used for surgical site preparation on the patient and for surgeons to
scrub hands and forearms prior to gowning and gloving
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Intermediate level disinfectants are often acceptable antiseptics
Principal antiseptics
Chlorhexidine
Considered more effective than the Iodophors
Available as tinctures, solutions, and detergents
Works by contact time, requires sufficient skin contact duration for effect
Iodophors
Available as tinctures, solutions, and detergents
Works by contact time similar to chlorhexidine
Principal antiseptics
Alcohol
Useful for low-level antisepsis
Has minimal residual effects
Evaporates rapidly and leaves no residue
Inhibited by organic debris
Not sufficient as the primary antiseptic per standard human and veterinary
surgical texts
Useful in conjunction with Iodophors or chlorhexidine
Breaks up surface oils and surface tension
 Part 9: Principles of Aseptic Surgery
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Aseptic Technique: A series of techniques used in the conduct of surgery that
prevent the contamination of the surgical site with infectious agents
This is not an absolute as surgical procedures almost always introduce
contaminants into the field
The goal is to lower the concentration of microorganisms to below the level
required for an infection to start
Aseptic Technique
Major bacteria involved in surgical wound infections are
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Staphylococcus aureus
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Streptococcus pneumoniae
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Pseudomonas multivorans (not a bacteria)
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Coagulasenegative Staphylococci
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Enterococcus spp
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Escherichia coli
In general, bacteria do not directly affect tissue cells
Bacterial waste products such as endotoxins and cytotoxins damage and kill cells
The body provides bacteria with food, shelter, humidity, and warmth
Generally, bacteria are localized until they gain entrance to the bloodstream, then
they become systemic infections
The body fights extracellular bacteria and other organisms in an antibody
mediated immune response
Briefly, antibodies recognize foreign bodies and call in phagocytes
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These phagocytes invaginate (envelope) and kill the bacteria, dying in the process
Immune response causes an increase in temperature, production of pus, and influx
of serous fluid
Surgical infections retard healing by:
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Damage from toxins
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Physical debris
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Changes in local circulation
Patient
Surgical preparation
Clean the site if needed
Some animals, especially livestock, may have large amounts of contaminants
(feces, dirt, bedding material) on their fur/skin
These contaminants may be removed prior to surgery with bathing or washing
Be aware that getting the animal wet may reduce their temperature, especially if
already anesthetized
Bathing is best performed the day prior to surgery
Surgical preparation
Remove excess hair
Hair should be clipped close to the skin around any potential incision sites.
An area should be clipped around this incision sufficient to create a surgical field
In rodents, this should be a minimum of 13 cm from the incision site
In larger animals, this should be a minimum of 46 cm from the incision site
Shaving with a blade is not generally recommended as skin trauma may lead to
increased bacterial counts
Clipping hair the day before surgery is associated with higher bacterial counts due
to skin trauma and should generally be avoided
All hair should be removed from the animal and prep site with a vacuum
For rodents, sticky tape may be used to remove hair instead of using a vacuum by
pressing the tape to the clipped hair
It is recommended that gloves be worn for the following steps to minimize
contamination from the technician’s hands
Correct attire should also be worn (discussed later)
Surgical preparation
Surgical scrub on the skin
A typical scrub consists of an application of Chlorhexidine or povidone iodine
scrub soaked gauze sponges followed with a wipe with 70% Isopropyl alcohol or
sterile water soaked gauze sponges
With oily or dirty skin, an initial wipe with 70% Isopropyl alcohol may be
performed to remove oils and reduce surface tension
Remember that the evaporation of alcohol may cause a significant loss of body
heat, particularly in rodents and neonates
May be reduced by heating the containers of prep solution in a 100-105 degree F
hot water bath
Alcohol soaked gauze sponges should be damp but not dripping wet
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Warm sterile water may also be used
This scrub should be performed 3-5 times
Each scrub should begin over the incision site and follow a concentric circle away
from the incision site
The same gauze sponge should never return to the incision site or a previously
cleaned area
When surgically preparing a limb, it may be useful to tape the foot to an IV stand
and suspend it for prepping
Start at the highest point and continue the concentric circles downwards (with
gravity)
When the final scrub has dried, apply povidone iodine or chlorhexidine solution
to the surgical site
Commonly the final 12 cycles of the surgical scrub and application of an
antiseptic solution is performed after the animal is moved to the operating room
(OR) and placed in proper recumbency
A povidone iodine film (i.e., 3M DuraPrep) may be applied instead of the
antiseptic solution
Allow the antiseptic solution or film to dry prior to draping
Surgical Mindset
If there is a question as to whether a step has been performed incorrectly, assume
that it has and start over
If there is suspicion that a prepped surgical site may have become contaminated,
redo the entire prep
If there is suspicion that a drape in the operating field has become contaminated
by contact with a non-sterile material replace it or, if this is impractical, cover the
suspected contaminated area with a new sterile drape
Surgical Positioning
The surgeon(s) should direct how the animal is positioned on the table
Surgeon’s often have positioning “quirks” which allow them to better visualize
the surgical site
Positioning is named by the part of the body in contact with the table
Right lateral recumbency = animal laying on its right side
Dorsal recumbency = animal laying on its back
Sternal or ventral recumbency = animal laying on its sternum
The animal may be kept in place with the aid of sandbags, troughs, rolled towels,
vacuum positioning “beanbags”, limb ties, or incisor clips (for rodents)
Care should be taken that limb ties do not occlude normal blood flow
For procedures where skull stability is important the animal may be placed in a
stereotaxic device
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Note, care must be taken to ensure that the clamps and earbars are not too
tight and cause skin or eardrum trauma
The Sterile Field
When the animal is properly positioned and antiseptically prepped for surgery, a
sterile field should be created
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Generally, a sterile field should be large enough to prevent accidental
contamination of the incision site(s), operating team, and sterile instruments and
equipment
Rodents
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At a minimum, a sterile fenestrated drape whose opening only uncovers
the surgical site is recommended
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Commonly the drape covers the entire animal

A paper drape can make it difficult to monitor respiratory and
cardiovascular functions during surgery

A clear plastic “Ziplock” bag can be cut into a flat sheet and gas sterilized
for use instead
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Allows easy viewing of the animal

Clear plastic adhesive surgical drapes may also be used

A table drape may also be placed prior to positioning the animal on the
table to enlarge the field
Non-rodents
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At a minimum, a sterile fenestrated drape sufficient to cover the animal
and surgical field is recommended

Sterile cloth or paper drapes may be used and should cover all areas
except those immediately about the incision site(s)
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Towel clamps may be used to affix the drape(s) in place

Alternatively, sterile surgical staples may be used

A sterile plastic adhesive incise drape (i.e., 3M Steridrape) may be placed
over the drape fenestration
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Extends the field to the edge of the incision and limits possible
contamination from exposed skin

Can be difficult to remove from instruments and equipment
 For rodents, sterile bandaging patches (i.e., Teguderm) are more
conveniently sized and may be used instead

Equipment such as drill cables, Carms, and imaging equipment that cannot
be sterilized and will be in the surgical field should be draped or covered
in sterile sleeves

It is convenient to sterilize light handles or provide sterile covers so that
sterile personnel can adjust operating lights during surgery
Special Cses
Draping limbs
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Easier on a suspended limb
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A surgeon may handle the unbandaged portion of the limb using a sterile
towel or drape
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Alternatively, an extra pair of sterile gloves may be worn and discarded
after draping
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These gloves should not come into contact with the drape or instruments
as they are no longer sterile
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The suspending tape should be cut close to the limb and a sterile
stockinette placed on the foot and unrolled towards the body
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The wrapped limb may be passed through a hole in the sterile drape
When the incision is made, the stockinette should be affixed about the
incision with towel clamps or staples
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Alternatively, the limb may be completely wrapped in sterile adhesive
drapes
Stereotaxic positioning
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Difficult to maintain sterility as the horizontal slides must be accessible
for movement of the manipulator arms yet must be used during
positioning of the animal prior to creation of the sterile field

Option 1:
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Drape over the animal and the stereotax
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Cut the drape over the slide(s) to be used
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Discard scissors
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Push the drape down under the slide
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Place the sterile manipulator arm on the slide

Place small drapes over the slide
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Option 2:

Cover the slide(s) to be used with a double cover of stockinette

Cut small holes to allow the ear bar clamps to protrude through the
stockinette
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Sterilize the slide frame assembly

Place the animal in the stereotax and prep

Cut the first stockinette away with sterile scissors and discard both
stockinette and scissors

Drape over the animal and stereotax

Cut the drape over the slide and the second stockinette

Clamp the stockinette to the drape and place the manipulator arm on the
slide
Surgical Personnel
Attire and operating personnel preparation
Street clothing, especially shoes, is a major source of contaminants
Street clothing should be replaced with clean scrub suits
Recommended to tuck scrub tops into pants to reduce the dispersion of skin debris
During hair clipping and prep a clean labcoat or Tyvek coverall can be worn to
protect the scrubs
Street shoes should be replaced with sanitized OR-specific shoes or covered with
shoe covers
Safety glasses are recommended and are mandatory for nonhuman primate
surgery
Surgical caps should be worn to prevent contamination from shedding hair
Facial hair should also be covered
Surgical masks should be worn to filter expired air
Masks are short-term filters only and should be replaced between surgical
procedures
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Exam gloves are helpful to minimize skin contaminants
Long-term exposure to antiseptic and cleaning solutions can be irritating to the
skin as well
Scrub with an antiseptic soap (chlorhexidine, povidone iodine)
Antiseptic solutions work by contact over time
Scrub should take ~10 minutes (~5 minutes per cycle) to allow sufficient time for
the antiseptic scrub to work
Hands should be kept higher than elbows during the entire process to maintain
drainage from hands down to elbows
Once the scrub is begun, hands and forearms should only touch sterile surfaces
If there are any breaks in technique, start over
Steps for a surgical scrub and donning a surgical gown

Wet hands and forearms

Apply antiseptic scrub to both hands and forearms

Scrub hands first, followed by forearms

Perform one cycle, rinse, repeat cycle, rinse

Anatomical (column) scrubs: scrub each skin surface (four sides of
fingers, top of hand, etc.), ten to fifteen times

Timed scrubs: scrub each surface for a set amount of time (~5 minutes per
cycle)

Some research suggests that a final covering with the antiseptic soap prior
to toweling dry enhances antimicrobial activity during surgery

Dry hands with a sterile towel
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Use opposite corners for each hand so that if one hand is unknowingly
contaminated the contaminants are not transferred to the other hand

Keep hands and forearms well away from scrubs and any nonsterile
surfaces

Hands are not sterile and should be considered to contaminate any sterile
objects that they touch
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Don a sterile gown
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Gowns should only be handled by inside surfaces so as to not contaminate
the outside of the gown
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Gowns may be picked up by the collar or the inside shoulder seams

If required, gently shake the gown to allow it to unfold completely

Slip arms into sleeves

Do not allow hands to protrude from the cuffs
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Sterile operating personnel

For batch surgeries of rodents, sterile gowns may be considered too
expensive or cumbersome

Consider wearing the same sterile gown for multiple surgeries or wearing
sterile Tyvek sleeves

Requires greater attention to possible instrument or device contamination
by touching nonsterile skin or scrubs

Don sterile gloves
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Closed gloving is recommended as it minimizes chances for
contamination

Open gloving may be used for changing gloves but has a much greater risk
of contamination

If a sterile assistant is available, it is preferable to have them put the glove
on the surgeon rather than open glove

Open gloving is useful when performing multiple rodent surgeries

Rinse gloves free of powder after donning
Closed Gloving
Step 1: Lay the glove on the cuff above the palm of the hand with the thumb side
down and fingers towards the elbow
Grasp the palm side of the glove through the cuff
Step 2: Grasp the top side of the glove with the other hand through the cuff
Step 3: Pull the cuff of the glove over the cuff of the gown
Advance fingers past the cuff and into the glove
Step 4: Pull the glove cuff as far down the sleeve as possible
If performed properly, the cuff of the gown should cover the back of the hand to
the fingers under the glove
Step 5: Repeat steps 1-4 with the other hand
Open Gloving
Step 1: Extend hands from sleeves
Contamination risk may be lessened by keeping the fingers of the assisting hand
below the gown cuff
Step 2: Grasp the inside of the glove’s cuff with the assisting hand
Step 3: Pull glove over the hand and gown sleeve
Do not unroll the glove cuff
Step 4: Slip the gloved fingers beneath the cuff of the other glove
Step 5: Slide hand into new glove and pull over hand and sleeve
Step 6: Taking care not to touch contaminated surfaces, unroll the glove cuffs
over the gown sleeves
Adjust the glove
Behavior in the operating room
Unnecessary movement disturbs air currents and can increase airborne
contaminants
Non-sterile objects such as equipment and non-sterilely gloved hands should not
be passed over sterile fields
The number of personnel in the OR should be kept to a minimum
Non-sterile personnel should keep clear of sterile areas
All personnel should always be watching for and bringing attention to any
compromise in sterility/aseptic technique
Attention should always be paid to the maintenance of a sterile field
Consider everything below the level of the table non-sterile
Gown portions, equipment cables, suction hoses, dropped instruments, etc.
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Backs of gowns are also considered non-sterile due to the difficulty in paying
attention to them
When not using them, keep hands above waist level
Clasping the hands reduces the chance of inadvertently brushing them against a
non-sterile object
Attention should always be paid to the maintenance of a sterile field
When passing other sterile personnel, pass back-to-back
Instruments which purposefully (i.e, scissors cutting drapes and coming into
contact with the contaminated underside) or accidentally (i.e, dropped off the
sterile field) become contaminated should be immediately discarded from the
sterile field
 Take all supplies in a sterile manner
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Surgical packs:
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Nonsterile personnel should open the outer wrap, taking care not to
contaminate the inside of the outer wrap or the inner wrap

Sterile personnel should open the inner wrap and either use the inner wrap
as part of the sterile field or remove the instruments from the pack
Surgical sleeves or foil packs
Nonsterile personnel should open these

Sleeves and foil packs should not be opened directly over the sterile field,
sterile personnel can remove the item from the sleeve or the nonsterile
person can flip it onto the sterile field
Sterile fluids

When opened, fluid should be poured from the bottle into a waste basket
to flush possible contaminants from the bottle mouth

Sterile personnel can pass the bowl under the stream until the bowl is
filled

Fluid should continue being poured until the bowl is removed from the
stream; this prevents draining of fluid along the nonsterile outer surface of
the bottle into the sterile bowl

Fluids can be taken from a bottle or bag with a septum with a needle and
syringe

Wipe the septum clean with a 70% Isopropyl alcohol wipe

A non-sterile person should hold the bottle or bag at a downward angle

The sterile person pushes the needle through the septum and aspirates
fluid

The needle is potentially contaminated and should be discarded
Surgical techniques
If there is a break in technique

If the drape becomes contaminated, cover with a fresh drape (adhesive
drapes work well for this)

If a glove or gown gets punctured, replace it immediately; evaluate any
instruments that might have been handled for contamination

If the incision site becomes contaminated, remove visible contaminants
and lavage with large quantities of sterile isotonic fluid
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Subsequent irrigation with povidone iodine or chlorhexidine solution may
be helpful

In any of these cases or when a break is discovered after the procedure is
completed, antibiotics may be used after consultation with a veterinarian

Pay careful attention to the animal for 23 weeks postsurgery and observe
for any signs of infection such as erythema, swelling, signs of pain and/or
discomfort, abnormal discharge, and loss of function
Rodent Surgical techniques
Rodents such as mice and rats do get infected

Rats are the most common model for infection in antibiotic testing

Small incisions, quick surgeries, and a good immune system coupled with
a fast metabolism may allow less stringent surgical conditions

Attention to aseptic technique is still required
Sterile drapes and surgical preps are recommended
Sterile gloves are recommended
Sterile gowns or sleeves may be useful
Part 10: Endoscopic Procedures

Section 10.1: General
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Endoscopy: “to look inside”
Usually reserved for the interior of hollow viscera (bronchi and intestinal tract)
Can be applied to laparoscopy and thoracoscopy as well
Also known as Minimally Invasive Surgery (MIS)
Surgical techniques designed to minimize the anatomic approach to the target
surgical site
Requires extensive equipment, training, and practice
Requires training not only for the operating personnel but also for the
preoperative and especially anesthesiology personnel
People must know their jobs and perform them properly without supervision
Require multiple steps and procedures
Packs should be easily available if the need arises to transform to an open
procedure
Room layout must be planned beforehand and orientated towards a smooth
operating flow and lack of obstruction
Surgeon(s) and camera operator needs easy viewing of the monitor

Section 10.2: Endoscopic Equipment
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Video-imaging equipment
Can be either flexible or rigid
Flexible endoscopes are usually used for GI and examination of the respiratory
system
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Rigid endoscopes (telescopes) are more commonly used
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Provide the most light

Provide the largest viewing field

Greatest resolution and clarity
Larger scopes provide more light and better fields of view
10 mm laparoscopes are preferred for most procedures
<5 mm laparoscopes are ideal for diagnostic laparascopy and thoracoscopy
Operating endoscopes are rigid scopes with channels for inserting instruments
such as biopsy collectors
Viewing fields may be straight (0 degrees) or at angles
Field of Vision: the borders of the field of view
The closer the tip of the endoscope is to the target tissue the greater the
magnification
Camera operator may need to adjust the focus
Endoscope must be attached to a camera, camera control unit, and monitor
Actually, the endoscope can be looked down like a telescope but this is poorly
suited for much beyond biopsies
Lights
Older systems use tungsten bulbs
Newer systems use mercury, xenon, or halogen bulbs and are significantly
brighter.
Brightness needs to be adjustable to prevent washing out the image
Are transmitted by fiberoptic cable
This bundle of cable should be clean at both ends and replaced when enough
(commonly 20%) of the cable break and fail
Camera
Use either one or three chips to convert the camera’s image into an electronic
signal to be sent to the monitor
Single-chip offers 450 lines of resolution
Three-chip uses a separate chip for red, green, and blue and offers 600 to 700
lines of resolution
Better systems avoid “whiteout” from glare reflected off light colored tissues
Camera Control Unit: Allows adjustment of the camera images and transmits
signal to the monitor

Can adjust focus, sharpness, etc.
Monitor
Offer resolution between 400 and 700 lines of resolution
Should be optimized for the camera chips used
Must be medical grade and properly grounded
May be ported to VHS systems for recording
Insufflator
Abdominal cavities are commonly filled with an inert gas (carbon dioxide or
nitrogen) to prevent collapse of the cavity and difficulty with surgery
Insufflator provides constant pressure in the cavity
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May be electronic or mechanical
Electrosurgery
Used for hemostasis and cutting
Ultrasonic or laser devices may also be used
Irrigation and Suction
Used to keep the surgical field clean and allow easy vision
Commonly combined into one device
Insufflation needles
Used to create a sealed breach into the abdominal cavity to administer gas
May be disposable or reusable
Trocars
Used to create “ports” for the entry of instruments and materials into the body
cavity
Is an obturator enclosed in a sleeve
Ports
A device that holds open an incision to allow passage of endoscopic instruments
into a body cavity
Ports may be placed by an open technique rather than using trocars

More time consuming

Useful when adhesions may be present or when trying to avoid organs
such as the rumen
Reducers
Act as additional gaskets inside or on top of the trocar for the maintenance of
pneumoperitoneum
Endoscopic surgical instruments are used and look identical to standard
instruments at the working end

The instruments are connected to a shaft which is passed through the
trocar or port

Section 10.3: Endoscopic Anesthesia

Differs from standard anesthesia due to the increased cavity pressure caused by
insufflation
Thoracic procedures usually do not use as the collapse of one lung and the rib
cage allow an open surgical site
Insufflation increases the abdominal pressure and pushes the diaphragm into the
chest cavity
Increased intraabdominal pressure (IAP) increases intrathoracic pressure and thus
requires mechanical ventilation at higher pressures than normal
PaCO2
Arterial carbon dioxide increases when the insufflation gas is CO2 by
transperitoneal absorption
If PaCO2 goes up, PaO2 goes down to compensate
This results in less O2 being free in blood
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Increase in heart rate
Increase in mean arterial pressure (MAP)
Increase vascular resistance
Decrease cardiac output
Decreases arterial and visceral blood flow
Positioning in Trendelberg (head down) or Fowler (head up) also shift pressures
in the abdomen and chest
Insufflation
For some procedures, an increased working space is needed in the chest and inert
gasses are introduced to expand the cavity
This can be dangerous as it limits lung capacity
Requires relatively little increases (5 mmHg) to clear space
EtCO2, MAP, heart rate, and CO will increase
Requires single lung ventilation
Standard endotracheal tubes inflate both lung equally
Defeats the purpose of insufflation
Single lung respiration requires specialized endotracheal tubes
The inferior lung receives 60% of the C.O.
Hypoxic pulmonary vasoconstriction (HPV) diverts blood flow from an
atelectatic lung
Inhalation anesthetics inhibit HPV, injectable barbituates commonly do not
Due to a constant and maintained pressure, liquids or inert gasses may by infused
between tissues to dissect them apart