GENERAL
ANAESTHETICS
CONTENT
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Definition
History
Principles of general anaesthesia
Difference between general and local anaesthetics
Difference between general anaesthetics and conscious
sedation.
Different stages of general anaesthesia
Pre-anaesthetic medication
Classification of general anaesthetics
Mechanism of action general anaesthetics
Drug interaction
Comparative study of general anaesthetics
Indications
Refferences
Anesthesia
• Anesthesia (an =without, aisthesis = sensation )
• Anesthesia is medication that attempts to eliminate
pain impulse from reaching the brain.
• In general anesthesia this is accomplished by putting
the patient asleep.
What is Anesthesia ???
• Anesthesia – is a reversible condition of comfort,
quiescence and physiological stability in a patient
before, during and after performance of a
procedure
• General anesthesia – for surgical procedure to
render the patient unaware / unresponsive to the
painful stimuli
– Drugs producing G. Anaesthesia – are called
General Anaesthetics
Larry D.(1992)
• General Anesthesia is a medically controlled
state of unconsciousness accompanied by a loss of
protective reflexes, including the inability to
maintain a patent airway independently and
respond purposefully to physical stimulation or
verbal command.
(ADA 1993)
General anesthetics (Defn.)
•
General Anaesthetics are the drugs which
produce reversible loss of all sensation and
consciousness, or simply, a drug that brings
about a reversible loss of consciousness
-Henderson JM(1988)
•
These drugs are generally administered by an
anesthesiologist in order to induce or maintain
general anesthesia to facilitate surgery
Historical Perspective
• Original discoverer of
general anesthetics
– Crawford Long: 1842,
ether anesthesia
• Chloroform introduced
– James Simpson: 1846
• Nitrous oxide
– Horace Wells
19th Century physician
administering chloroform
• William Morton
– October 16, 1846
– Gaseous ether
– Public demonstration
gained world-wide
attention
– Public demonstration
consisted of an operating
room, “ether dome,”
where Gilbert Abbot
underwent surgery in an
unconscious state at the
Massachusetts General
Hospital
• Ether no longer used in
modern practice, yet
considered to be the first
“ideal” anesthetic
• Cyclopropane: 1929
– Most widely used general
anesthetic for the next 30 years
• Halothane: 1956
– Team effort between the British
Research Council and chemists
at Imperial Chemical Industries
– Preferred anesthetic of choice
• Thiopental(1960):
Intravenous anesthetic
Principles of General Anesthesia
• Minimizing the potentially
harmful direct and indirect
effects of anesthetic agents
and techniques
• Sustaining physiologic
homeostasis during surgical
procedures
• Improving post-operative
outcomes
Discription
General Anesthetics
Local Anesthetics
1. Site of action
Central Nervous System
Peripheral Nerves
2.Area of body involved Whole body
Restricted area
3. Consciousness
Lost
Unaltered
4. Major surgery
Preferred
Can not be used
5. Minor surgery
Can not be used
Preferred
6. Care of vital function
Essential
Usually not needed
Difference Between General Anesthetics and
Conscious Sedation
General Anesthetics
Conscious Sedation
Consciousness Lost
Consciousness is depressed
Protective reflexes are lost
Protective reflexes are maintained
Inability to respond purposefully to
physical stimulation or verbal
command.
Permits appropriate response by the
patient to physical stimulation or
verbal command
Major surgery are Preferred
Can not be used
Not preferred for minor surgery
Preferred for minor surgery
Care of vital function is essential
Care of vital function is essential
Criteria For Pediatric Patient Under GA
• Smith et al (1978) estimated that pediatric dental patients of
age group between 2-5 years will require GA for dental
treatment to be successfully completed.
• Trapp (1982) given 2 indication for pediatric GA
1.
2.
Healthy patient who is unable to co operate for office procedure
after standard management armamentarium
Patient who is medically compromised and unable to tolerate
routine dental procedure
Guideline for the use
of general anesthesia for pediatric patients.
• Patients with certain physical, mental or medically
compromising conditions
• Extremely uncooperative
• Fearful, anxious or physically resistant children or adolescents
with substantial dental needs and no expectation that the
behaviour will improve soon
(AAPD 2005)
American Society of Anesthesiologists Classification (Modified)
Class
Physical status
I
a normally healthy patient with no organic, physiologic, biochemical or psychiatric
disturbance, or disease.
II
a patient with mild-to-moderate systemic disturbance or disease.
III
a patient with severe systemic disturbance or disease.
IV
a patient with severe and life-threatening systemic disease or disorder.
V
a moribund patient who is unlikely to survive without the planned procedure.
VI
a patient declared brain-dead whose organs are being removed for donor purposes.
E
emergency operation of any variety; used as a modifier.
(AAPD 2004)
Preoperative assessment
• All paperwork (consent form, history, physical
examination, and laboratory test results) should be
reviewed before the patient arrives for surgery
• The purpose of the evaluation is to identify
patients at an increased risk for complications
based on their past history their current state of
general health and any pertinent physical findings
that may influence the safety, known drug
reactions.
Preoperative Preparation
• Pre-operative verbal and written instructions must be
given to the patient, parent, escort, guardian or care
giver.
• Patients should be encouraged to continue all their
chronic medications up to the time that they arrive for
the surgery.
• Oral medications can be taken with a small amount of
water up to 1 hour before surgery
Appropriate Intake Of Food And Liquids
Before Surgery
Ingested Material
Minimum
Fasting Period
(h)
Clear liquids: water, fruit juices without pulp, carbonated beverages,
clear tea, black coffee
2
Breast milk
4
Infant formula
6
Nonhuman milk: because nonhuman milk is similar to solids in
gastric emptying time, the amount ingested must be considered when
determining an appropriate fasting period
6
Light meal: a light meal typically consists of toast and clear liquids.
Meals that include fried or fatty foods or meat may prolong gastric
emptying time. Both the amount and type of foods ingested must be
considered when determining an appropriate fasting period
6
AAPD(2006)
Patient Evaluation And Preparation:
• The child should have had a complete
physical evaluation.
• The Physical evaluation should include the
following:
– Vital signs
– Evaluation of airway patency
– ASA classification.
• The six vital signs are as follows:
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Blood pressure (BP)
Heart rate (pulse) and rhythm
Respiratory rate
Temperature
Height
Weight
• Laboratory testing is done
- Complete hemogram
- Urine examination
- Chest x-ray
It is the use of drugs prior to anesthesia to make it
more safe and pleasant.
• To relieve anxiety – benzodiazepines.
• To prevent allergic reactions – antihistaminics.
• To prevent nausea and vomiting – antiemetics.
• To provide analgesia – opioids.
• To prevent bradycardia and secretion – atropine.
1. Sedative-anti anxiety drug => diazepam(5mg),
lorazepam (2mg-0.02mg/kg).
2. Anticholinergic drugs => Atropine and hyoscine
are use to reduce salivary & bronchial secretions.
3. H2 Blockers => Famotidine , & ranitidine are use
to reduce the PH & gastric juice.
4. Proton pump inhibitors => Omeperazole,
5. Antiemitic => metoclopramide (10-20 mg)
6. 5HT blockers => ondensetron (4-8 mg iv)
Stages and signs of Anesthesia
• Traditional Description of signs and stages of
GA - Also called Guedel`s sign (1937)
•Descending depression of CNS
• Higher to lower areas of brain are involve
• Vital centers located in medulla are paralyzed last
Stages of GA
Stage I: Stage of Analgesia
• Starts from beginning of anaesthetic inhalation and lasts
upto the loss of consciousness
• Pain is progressively abolished during this stage
• Patient remains conscious, can hear and see, and feels a
dream like state
• Reflexes and respiration remain normal
• It is difficult to maintain - use is limited to short
procedures only
Stage II: Stage of Delirium and Excitement:
• From loss of consciousness to beginning of irregular
respiration
• Excitement - patient may shout, struggle and hold his breath
• Muscle tone increases, jaws are tightly closed.
• Breathing is jerky; vomiting, involuntary micturition or
defecation may occur.
•Heart rate and BP may rise and pupils dilate due to
sympathetic stimulation.
•No operative procedure carried out during this stage.
•This stage is not found with modern anaesthesia –
preanaesthetic medication, rapid induction .
• Stage III: Stage of Surgical anaesthesia
– Extends from onset of irregular respiration to cessation
of spontaneous breathing. This has been divided into 4
planes:
– Plane 1: Roving eye balls. This plane ends when eyes
become fixed.
– Plane 2: Loss of corneal and laryngeal reflexes.
– Plane 3: Pupil starts dilating and light reflex is lost.
– Plane 4: Intercostal paralysis, shallow abdominal
respiration, dilated pupil.
Stage IV: Medullary / respiratory paralysis
• Cessation of breathing
failure of
circulation
death
• Pupils: widely dilated
• Muscles are totally flabby
• Pulse is imperceptible
• BP is very low.
But not seen these days, because!
• Availability of rapidly acting agents – IV as well as
Inhalation
• Mechanical control of Respiration
• Pre-operative and post operative Drugs
• Important signs observed by anaesthetists:
– If no response to Painful stimulus - stage III
– On Incision - rise in BP, respiration etc. – light anaesthesia
– Fall in BP, respiratory depression – deep anaesthesia
• Modern methods: Monitoring of Vital signs by CAM
(computer assisted monitoring)
Intra-Procedure Monitoring
• Prior to the administration of any sedation
medication, an assessment is completed. The
clinical staff is available to evaluate the patient’s
condition every 5 to 15 minutes during the
sedation procedure.
• This monitoring consists of respiratory
rate/rhythm, pulse rate/rhythm, peripheral
perfusion, pulse oximetry, and blood pressure.
Intra-Procedure Monitoring
• Monitoring devices, such as electrocardiography
(ECG) machines, pulse oximeters (with sizeappropriate oximeter probes), end-tidal carbon
dioxide monitors, and defibrillators
• In certain procedures MRI, and CT Scan are used.
• The frequency of monitoring depends on the
patient’s condition, and is at the discretion of the
physician performing the procedure.
• Oxygenation:
– Color of mucosa, skin or blood must be
continually evaluated.
– Oxygenation saturation must be evaluated
continuously by pulse oximetry
• Ventilation:
– Intubated patient: End-tidal CO2 must be
continuously monitored and evaluated.
– Non-intubated patient: Breath sounds via
auscultation and/or end-tidal CO2 must be
continually monitored and evaluated.
– Respiration rate must be continually monitored
and evaluated.
• Circulation:
– The dentist must continuously evaluate heart
rate and rhythm via ECG throughout the
procedure, as well as pulse rate via pulse
oximetry.
– The dentist must continually evaluate blood
pressure.
• Temperature:
– The equipment to continuously monitor body
temperature should be available and must be
performed whenever triggering agents
associated with malignant hyperthermia are
administered.
Emergency Equipment That May Be Needed
to Rescue a Patient
Intravenous Equipment
• Assorted IV catheters
• Tourniquets
• Alcohol wipes
• Adhesive tape
• Assorted syringes
• IV tubing
Pediatric drip (60 drops/mL)
Pediatric burette
Adult drip (10 drops/mL)
Extension tubing
3-way stopcocks
•IV fluid
Lactated Ringer solution
Normal saline solution
•D5 0.25 normal saline solution
•Pediatric IV boards
•Assorted IV needles
•Intraosseous bone marrow needle
•Sterile gauze pads
AAPD(2006)
Techniques of inhalation GA
• Open drop method
• Through anesthetic machines
- Open system
- Closed system
- Semi-closed system
Continuous flow (Boyle’s)
anaesthetic machine
Anaesthetic Machine
(Boyle’s equipment)
• The anaesthetic machine
• Gas source- either piped gas
or supplied in cylinders
• Flow meter
• Vaporisers
• Delivery System or circuit
Henry Boyle in 1917
Purposes Of The Anesthetic Machine
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Provide oxygen
Deliver precise amounts of anesthetic agent
Remove CO2
Provide assisted or controlled ventilation to the
patient
Drugs That May Be Needed
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Albuterol for inhalation
Ammonia spirits
Atropine
Diphenhydramine
Diazepam
Epinephrine (1:1000, 1:10
000)
• Flumazenil
• Glucose (25% or 50%)
• Lidocaine (cardiac lidocaine,
local infiltration)
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Lorazepam
Methylprednisolone
Naloxone
Fosphenytoin
Racemic epinephrine
Sodium bicarbonate
Succinylcholine
AAPD(2006)
Albuterol (Proventil)
• Sympathomimetic that is selective for beta
2 it also relaxes the smooth muscle of the
brachial tree and peripheral vasculature
• Indications
– Relief of bronchospasm
– Prevention of exercise induced bronchospasm
Albuterol (Proventil)
• Contraindications
– dysrhythmia's associated with tachycardia
• Dose
– Unit dose 0.083%
– 2.5 mg diluted to 3 ml
Aspirin
• Analgesic, anti-inflammatory, antiplatelet
• Indications
– AMI
• CI
– Only systemic sensitivity in the context of MI
• Dose
– 160-325 mg PO (preferably chewed)
Atropine Sulfate
• Anticholinergic
• Indications
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–
–
–
–
Symptomatic bradycardia
Asystole
PEA
ACE inhibitor OD
Exercise induced bronchospastic disorders
Atropine Sulfate
• CI
– Tachycardia
– Obstructive disease of GI tract
– Unstable cardiovascular status in the context of
cardiac ischemia & hemorrhage
– Narrow angle glaucoma
Atropine Sulfate
• Dose
– Bradydysrhymia’s
• 0.5-1.0mg q 5 min to a max of 0.03-0.04 mg/kg
– Asystole
• 1.0 mg IV or ETT(dilute to 10 ml)
– ACE inhibitors
• 2mg IVP q 5-15 minutes (no max)
Dextrose 50%
• Dextrose is the 6 carbon sugar that is the
principal carbohydrate used by the body.
• Indications
– Hypoglycemia
– Coma/seizure of unknown etiology
Dextrose 50%
• Contraindications
– Intracranial hemorrhage
– Increased intracranial pressure
• Dose
– 12.5-25 G IV slowly
Diazepam (Valium)
• Contraindications
–
–
–
–
in coma (unless there is seizure activity)
CNS depression as a result of head injury
respiratory depression
Shock
• Dose
– 5mg over 2 min IV q 10-15 min
– Max dose is 30mg
Epinephrine (Adrenalin)
• Sympathomimetic
• Indications
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–
–
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Bronchial asthma
Acute allergic reaction
Cardiac arrest
Profound symptomatic bradycardia
Epinephrine (Adrenalin)
• Contraindications
– Hypovolemia shock- correct volume deficit
– Use with caution in coronary insufficiency
• Dose
– Cardiac arrest
• 1 mg IVP q 3-5 min
• 2.5 times the normal dose if via ETT
Epinephrine (Adrenalin)
• Dose
– Drips
• Mix 1 mg ampule in 500 ml (2 mcg/ml) and infuse
at 1-2 mcg/min titrate to desired response
– Anaphylactic reaction
• Mild- 0.3-0.5 mg (1:1000) SQ
• Severe- 1-2 ml (1:10000) slow IV
Flumazenil (Romazicon)
• Benzodiazepine antagonist
• Indications
– Reversal of BZD
• Contraindications
– TCA OD
– Cocaine or other stimulant intoxication
Flumazenil (Romazicon)
• Dose
– 0.2mg IV over 30 seconds
– Additional dose of 0.3mg after 30 seconds
– Additional dose of 0.5mg at 1 min intervals
– Max of dose of 3 mg
Lidocaine (Xylocaine)
• Antidysrhythmic
• Indications
– VT/VF
– Wide complex tachycardia of uncertain origin
– Significant ventricular ectopy in the setting of
MI
Lidocaine (Xylocaine)
• Contraindications
– Adams-Stokes Syndrome
– 2nd or 3rd degree HB in the absence of a
pacemaker
• Dose
– 1.0-1.5 mg/kg consider repeat in 3 min
– Total IV dose is 3 mg/kg
Lidocaine (Xylocaine)
• Dose
– ETT is 2.5 times IV dose
– Main infusion is 2G in 500 (4mg/ml)
• Run @ 2-4 mg/min
• Practice Pearls
– 75-100 mg bolus will maintain level for 20
mins
– If bradycardia is present treat PVC’s with
Atropine
Naloxone (Narcan)
• Opiod antagonist
• Indications
– Narcotic OD
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•
•
•
Morphine, heroin, hydromophone
Methadone, meperidine, paregoric
Fentanyl, oxycodone, codeine
Propoxyphene
– Coma unknown origin
Naloxone (Narcan)
• Contraindications
– Use with caution in addicted pts may
precipitate violent withdrawal issues.
• Dose
– 0.4-2mg IV, IM, SQ or ETT (dilute)
Nitroglycerin (Nitrostat)
• Vasodilator
• Indications
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–
–
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Ischemia chest pain
Pulmonary hypertension
CHF
Hypertensive emergencies
Nitroglycerin (Nitrostat)
• Contraindications
– Hypotension
– Head injury
– Cerebral hemorrhage
• Dose
– 0.15-0.6 mg SL q 5 minutes (3 max)
– Infusion- 200-400 mcg/ml @ 10-20 mcg/min
increase by 5-10 prn.
Norepinephrine (Levophed)
• Sympathomimetic
• Indications
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–
–
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Cardiogenic shock
Neurogenic shock
Inotropic support
Hemodynamically significant hypotension
refractory to other sympaths
Norepinephrine (Levophed)
• Contraindications
– Hypotensive pts with hypovolemia
• Dose
– Dilute
Vasopressin
• Naturally occuring hormone (ADH)
• Indications
– May be used as an alternate vasopressor in
cardiac arrest
– May be useful in hemodynamic support of
dilatory shock
Vasopressin
• Contraindications
– Not recommended for responsive pts with CAD
• Dose
– 40 U IV push- one dose only (buys you about
10 min)
Sodium Bicarbonate
• Buffer, alkalinizing agent, electrolyte
• Indications
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Known bicarbonate responsive acidosis
On return of ROSC following long arrest
Intubated pt with long arrest interval
PEA/DKA
TCA OD
Metabolic acidosis
Sodium Bicarbonate
• Contraindications
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Chloride loss from vomiting & GI
Met or resp alkalosis
Severe pulmonary edema
Abdominal pain of unknown origin
Hypo;
• Calcemia, kalemia, natremia
Sodium Bicarbonate
• Dose
– 1 mEq/kg IV with 0.5 mEq/kg repeat q 10 min
Normal Pediatric vital signs
Age
Pulse rate
Blood Preassure
Respiratory Tidal
Rate
Volume
3 years
101 +/- 15
100/67 +/- 25/23
24 +/- 6
112
5 years
90 +/- 10
94/55 +/- 14/9
23 +/- 5
270
12 years 70 +/- 17
109/58 +/-16/9
19 +/- 5
480
Adult
122/30 +/- 30/20
12 +/- 3
575
77 +/- 5
Classification
•
Inhalation:
1.
2.
Gas: Nitrous Oxide
Volatile liquids:
• Ether
• Halothane
• Enflurane
• Isoflurane
• Desflurane
• Sevoflurane
• Intravenous:
1. Inducing agents:
• Thiopentone,
Methohexitone sodium,
propofol and etomidate
2. Benzodiazepines (slower
acting):
• Diazepam, Lorazepam,
Midazolam
3. Dissociative anaesthesia:
• Ketamine
4. Neurolept analgesia:
• Fentanyl
Anesthesiology
There are two types of anesthetics :
 Inhalational --- for maintenance
 Intravenous --- for induction and short
procedures
Inhalation anesthetics:
 Advantage of controlling the depth of
anesthesia.
 Metabolism is very minimal.
 Excreted by exhalation.
Hypotheses of General
Anesthesia
• Lipid Theory by Meyer (1899) and Overton (1901)]: based on the fact
that anesthetic action is correlated with the oil/gas coefficients.
•
•
•
The higher the solubility of anesthetics in oil, the greater is
the anesthetic potency.
Meyer and Overton rule baised on their observation suggested
that the logarithm of the efficacy of an anaesthetic was related
to the logarithm of its hydrophobicity.
The Meyer–Overton rule was found to be only approximate,
and a number of compounds do not fit the rule e.g. the
homologous series of 1-alkanols have greater efficacy than the
rule would predict
(Mullins, 1954; Cantor, 2001).
Mechanisms of GA
• For inhalation anesthetics – Minimum Alveolar
Concentration (MAC) is defined as the minimum alveolar
concentration that prevents movement in response to
surgical stimulation in 50% of subjects. Correlates with
oil/gas partition coefficient
• Practically –
• Alveolar concentrations can be monitored
continuously by measuring end-tidal anesthetic
concentration using spectrometry
• End point (immobilization) – can me measured.
(MAC explains only capacity of anesthetics to enter in
CNS and attain sufficient concentration, but not actual
MOA)
Mechanisms of GA
• For Intravenous agents – Potency of IV agent is defined
as the free plasma concentration (at equilibrium) that
produces loss of response to surgical incision in 50% of
subjects.
• Difficult to measure:
– no available method to measure blood or plasma
concentration continuously
– Free concentration at site of action cannot be
determined
Modern theory on Mechanism of
General Anesthesia
• Major targets – ligand gated ion channels
• Important one – GABAA receptor gated
Cl¯ channel
– Examples – Many inhalation anesthetics,
barbiturates, benzodiazepines and propofol
– Potentiate the GABA to open the Cl¯ channels
Structure of GABAA
• GABAA receptors - 4
transmembrane (4-TM) ion
channel
– 5 subunits arranged around a
central pore: 2 alpha, 2 beta, 1
gamma
– Each subunit has N-terminal
extracellular chain which contains
the ligand-binding site
– 4 hydrophobic sections cross the
membrane 4 times: one
extracellular and two intracellular
loops connecting these regions, plus
an extracellular C-terminal chain
GABAA Receptor gated Cl¯ Channel
• Normally, GABAA receptor mediates the effects
of gamma-amino butyric acid (GABA), the major
inhibitory neurotransmitter in the brain
– GABAA receptor found throughout the CNS
• most abundant, fast inhibitory, ligand-gated ion channel in the
mammalian brain
• located in the post-synaptic membrane
• Ligand binding causes conformational changes leading to
opening of central pore and passing down of Cl- along
concentration gradient
• Net inhibitory effect reducing activity of Neurones
– General Anaesthetics bind with these channels and
cause opening and potentiation of these inhibitory
channels – leading to inhibition and anaesthesia
• Receptor sits on the
membrane of its neuron at
the synapse
• GABA, endogenous
compound, causes GABA
to open
• Drugs (GA) don't bind at
the same side with GABA
• GA receptors are located
between an alpha and
beta subunit
Mechanism of GA – contd.
Other Mechanisms:
• Glycine – Barbiturates, propofol can
activate in spinal cord and medulla
• N – methyl D- aspartate (NMDA) type of
glutamate receptors - Nitrous oxide and
ketamine selectively inhibit
Anesthetic
Suppression of
Physiological
Response to
Surgery
Pharmacokinetics of Inhaled Anesthetics
1. Amount that reaches the brain
1.
Indicated by oil:gas ratio (lipid solubility)
2. Partial Pressure of anesthetics
3. Solubility of gas into blood
1.
The lower the blood:gas ratio, the more anesthetics will arrive at
the brain
4. Cardiac Output
1.
Increased CO= greater Induction time
Pathway for General Anesthetics
The important characteristics of
Inhalational anesthetics which govern the
anesthesia are :
• Solubility in the blood
(blood : gas partition co-efficient)
• Solubility in the fat (oil : gas partition coefficient)
Blood : gas partition co-efficient:
 It is a measure of solubility in the blood.
 It determines the rate of induction and recovery
of Inhalational anesthetics.
 Lower the blood : gas co-efficient – faster the
induction and recovery – Nitrous oxide.
 Higher the blood : gas co-efficient – slower
induction and recovery – Halothane.
Rate of Entry into the Brain: Influence of
Blood Solubility
Oil: gas partition co-efficient:
• It is a measure of lipid solubility.
• Lipid solubility - correlates strongly with
the potency of the anesthetic.
• Higher the lipid solubility – potent
anesthetic.
Higher the Oil: Gas
Partition Co-efficient
lower the MAC .
E.g., Halothane
0.8
1.4
220
Variables that Control Partial Pressure in
Brain
• Direct Physician's Control
– Solubility of agent
– Concentration of agent in inspired by air
– Magnitude of alveolar ventilation
• Indirect Physician’s Control
– Pulmonary blood flow-function of CO
– Arteriovenous concentration gradient
General Actions of Inhaled Anesthetics
• Respiration
– Depressed respiration and response to CO2
• Kidney
– Depression of renal blood flow and urine output
• Muscle
– High enough concentrations will relax skeletal
muscle
Cont’
• Cardiovascular System
– Generalized reduction in arterial pressure and
peripheral vascular resistance. Isoflurane
maintains CO and coronary function better than
other agents
• Central Nervous System
– Increased cerebral blood flow and decreased
cerebral metabolism
Nausea And Vomitting
GENERAL ANAESTHETICS
post operative
period
Stimulate CTZ and brain stem
vomiting center
Nausia and vomiting
Post-anesthesia Discharge
Scoring (PADS)
1. Vital signs, including blood pressure, heart
rate, respiratory rate, and temperature
2. Ambulation and mental status
3. Pain and PONV
4. Surgical bleeding and
5. Fluid intake/output
Post-anesthesia Discharge Scoring (PADS) System
• Vital Signs
• 2-Within 20% of the preoperative value
• 1 -20%-40% of the preoperative value
• 0-40% of the preoperative value
• Ambulation
• 2 -Steady gait/no dizziness
• 1-With assistance
• 0-No ambulation
• Nausea and Vomiting
• 2-Minimal
• 1-Moderate
• 0-Severe
• Pain
• 2-Minimal
• 1-Moderate
• 0-Severe
• Surgical Bleeding
• 2-Minimal
• 1-Moderate
• 0-Severe
Toxicity and Side Effects
•
•
•
•
Depression of respiratory system
Depressed cardiovascular system
Gaseous space enlargement by NO2
Fluoride-ion toxicity from methoxyflurane
– Metabolized in liver = release of Fluoride
ionsDecreased renal function allows fluoride to
accumulate = nephrotoxicity
Toxicity and Side Effects
• Malignant hyperthermia
– Malignant hyperthermia is disease passed down
through families that causes a fast rise in body
temperature (fever) and severe muscle
contractions when the affected person
gets general anesthesia.
– Rapidly cool the individual and administer
Dantrolene or beta-blocker to block
sarcoplasmic reticulum release of Calcium.
Inhalational anesthetics
Nitrous oxide:
• Safest inhalational anesthetic.
• Weak anesthetic but a good analgesic.
• No toxic effect on the heart, liver and kidney.
• Caution about diffusional hypoxia
megaloblastic anemia.
• Victor C(2007) revived that nitrous oxide can have
significant metabolic effects in settings of abnormal
vitamin B12 and B12-related metabolism in children.
These conditions can be genetic or environmental.
Symptoms may not appear until days to weeks after
exposure to nitrous oxide.
• Syed Mushtaq Gilani(2008) revived that omitting of
N2O from anesthetic regimen has a substantial impact on
patient comfort after surgery by reducing incidence of
PONV and it does not have any justifiable indication of its
use in General anesthesia
Halothane(Fluothane):
• It is a potent anesthetic.
• Induction is pleasant.
• It sensitizes the heart to catecholamines.
• It dilates bronchus – preferred in asthmatics.
• It inhibits uterine contractions.
• Halothane hepatitis and malignant hyperthermia
can occur.
• Habre W (1996) studied the changes in respiratory
mechanisms when propofal and halothane were used as
anestheics. Changes in respiratory mechanism were
significant when propofal used as anesthetic in both the
children with or without asthma such as respiratory
system resistance dynamic compliance, in case of
halothane the changes of respiratory mechanism were not
clinically relevant
• Bather A. et al (1997) studied the difference in
Sevoflurane and Halothane as anesthetics and conclude
that lack of significant differences in VAS scores suggests
that the speed of induction, the speed of emergence, and
the quality of induction are similar under clinical
conditions. Any purported benefits of sevoflurane seem to
be of minor consequence.
Enflurane:
• Sweet and ethereal odor.
• Generally do not sensitizes the heart to
catecholamines.
• Seizures occurs at deeper levels –
contraindicated in epileptics.
• Caution in renal failure due to fluoride.
• Wang X et al. (2008)MAC of enflurane in infants
older than 6 months is similar to that in young
children. The MAC of enflurane decreases with
co-administration of fentanyl in the pediatric
population.
Isoflurane:
• It is commonly used with oxygen or nitrous
oxide.
• It do not sensitize the heart to
catecholamines.
• Its pungency can irritate the respiratory
system.
Desflurane:
• It is delivered through special vaporizer.
• It is a popular anesthetic for day care surgery.
• Induction and recovery is fast, cognitive and
motor impairment are short lived
• It irritates the air passages producing cough
and laryngospasm.
• Andreas Redel et al.(2009) Comparison of isoflurane-,
sevoflurane-, and esflurane-induced pre- and
postconditioning against myocardial infarction in mice in
vivo and conclude that the potency of volatile anesthetics
to reduce myocardial infarct size in mice significantly
increases from ISO over SEVO to DES,
Sevoflurane:
• Induction and recovery is fast.
• It is pleasant and acceptable due to lack of
pungency.
• It do not cause air way irritancy.
• Concerns about nephrotoxicity.
• Epstein RH et. al.(1995 )Compared vital signs and
the speed of induction and emergence with
sevoflurane versus halothane in pediatric patients.
Induction and emergence from anesthesia was
faster with sevoflurane than halothane. Vital signs
were more stable with sevoflurane during
induction through intubation, and were
comparable during maintenance. Sevoflurane is an
excellent drug for inhalational induction in
pediatric patients.
Inhalation
Anesthetic
Nitrous oxide
MAC value %
>100
Oil: Gas
partition
1.4
Desflurane
7.2
23
Sevoflurane
2.5
53
Isoflurane
1.3
91
Halothane
0.8
220
Anesthetic
B:G PC
O:G PC
Features
Note
Halothane
2.3
220
PLEASANT
Enflurane
1.9
98
PUNGENT
Arrhythmia
Hepatitis
Hyperthermia
Seizures
Hyperthermia
Isoflurane
1.4
91
PUNGENT
Widely used
Sevoflurane 0.62
53
PLEASANT
Ideal
Desflurane
0.42
23
IRRITANT
Cough
Nitrous
0.47
1.4
PLEASANT
Anemia
Intravenous anesthetics
Parenteral anesthetics (IV):
• These are used for induction of anesthesia.
• Rapid onset of action.
• Recovery is mainly by redistribution.
• Also reduce the amount of inhalation anesthetic
for maintenance.
• E.g., includes thiopental, propofol, etomidate,
ketamine.
Thiopental (Pentothal ®):
• It is an ultra short acting barbiturates.
• Consciousness regained within 10-20 mins by
redistribution to skeletal muscle.
• It do not increase ICP.
• It is eliminated slowly from the body by
metabolism and produce hang over.
• It can be used for rapid control of seizures.
Dosage
• Thiopental Sodium Dosage for Sedation Based
on Child’s Weight and Age
Age of
ChildDosage
<6 months
50 mg/kg
6 months to 1 year
35 mg/kg
>1 year
25 mg/kg
(maximum 700 mg)
• Younger patients require relatively larger doses
than middle-aged and geriatric adults.
• In adults - 25–50 mg/kg
Propofol (Propovan ®):
• Most commonly used IV anesthetic.
• Unconsciousness in ~ 45 seconds and
~15 minutes.
• Anti-emetic in action.
• Suited for day care surgery - residual
impairment is less marked.
lasts
Dosage
• Dose in children up to 8 years is 2.5 mg/kg
• Most adult patients aged less than 55 years are
likely to require 2.0 to 2.5 mg/kg
• It should be administered at the rate of 2 ml (20
mg) every 10 seconds till the clinical signs show
the onset of anesthesia.
• Jan P. Mulier (1991) compared cardiodynemic effect of
propofol and thiopental and concluded that the cardiodepressant effects of propofol are more pronounced and
more prolonged than those of equipotent doses of
thiopental when given as a single bolus.
• Pranas S(2010) stated that Propofol is a safer agent with a
lower rate of side effects as compared to thiopental when
performing cardioversion in patients with persistent AF
and depressed left ventricular function.
Etomidate (Amidate ®):
• It is a short acting anesthetic.
• It suppress the production of steroids from the
adrenal gland and no repeated injections.
• It is a pro-convulsant and emetic.
• CVS stability is the main advantage over
anesthetics.
Dosage
• Adult: 300 mg/kg given slowly over 30-60
seconds into a large vein in the arm.
• Child: Up to 30% more than the standard adult
dose
• Elderly: 150-200 mg/kg, subsequently adjusted
according to effects
Ketamine (Ketalar ®): Dissociative anesthesia
• Produce - profound analgesia, cataleptic state,
immobility, amnesia with light sleep.
• Acts by blocking NMDA receptors
• Heart rate and BP are elevated due to
sympathetic stimulation.
• Respiration is not depressed and reflexes are
not abolished.
• Emergence delirium, hallucinations and
involuntary movements occurs in 50% cases
during recovery.
• It is useful for burn dressing and trauma
surgery.
• Ketamine have been used for operations on the
head and neck.
• Dangerous for hypertensive and IHD.
Dosage
• The usual dose of ketamine is 1-2mg/kg in
children
• Supplemental doses of 1/3 to 1/2 of initial
dose
• In adults it ranges from Range: 1-4.5 mg/kg
• Cámara RC et al. (2008) investigated the effects of
ketamine anesthesia on the motility alterations and tissue
injury caused by ischemia/reperfusion in rats. They
conclude that that ketamine anesthesia is associated with
diminished intestinal injury and abolishes the intestinal
transit delay induced by ischemia/reperfusion.
• Fernande Lois and Marc De Kock (2008) reviewed the
place of the old anesthetic ketamine in pediatric
anesthesia. They conclude ketamine is highly effective
against surgery and opiate-induced hyperalgesia. It has
original antiproinflammatory properties. i.e. it promotes
self-limitation of the inflammatory response that follows
surgery. In the pediatric population, these benefits yet to be
confirmed.
Neuroleptanalgesia :
• It is characterized by general quiescence,
psychic indifference and intense analgesia
without total loss of consciousness.
• Combination of Fentanyl and Droperidol as
Innovar
Neuroleptanalgesia :
• It is associated with decreased motor
functions, suppressed autonomic reflexes,
cardiovascular stability with mild amnesia.
• It causes drowsiness but respond to
commands.
• Used for endoscopies, angiography and minor
operations.
Anesthetic
I.V
Duration
mins
Thiopental
5 - 10
Propofol
Ketamine
Analgesia
Muscle
relaxation
Others
---
---
Respiratory
depression
5-10
---
---
Respiratory
depression
5-10
+++
---
Hallucinations
• Nitrous oxide (50%) has been used with oxygen for
dental and obstetric analgesia.
• Isoflurane ,Desflurane is preferred for neurosurgery.
• Sevoflurane is suitable both outpatient as well as
inpatient.
• Thiopentone Ocationally used for control of
convulsion.
• Propofol : injection and perfusion is frequently
used for total i.v. anaesthesia when supplemented
by fentanyl.
• Kitamine is dengerous for hypertensives ,in
ischemic heart disease.
• Halothane is not given in liver disease.
• Sevoflurane is not given to sever hepatic
dys function , jaundice, fever .
• Nitrous oxide Is contraindicated in first two
trimester of pregnency because its effect on
DNA production => undesirable out comes.
Farsi N (2009)
• Review of post-operative morbidity reports for
pediatric dental care under general anesthesia
show great variations.
• Inability to eat (86%), sleepiness (71%), and pain
(48%) were the most common complaints in the
first day, followed by bleeding (40%), drowsiness
(39%), sore throat (34%), vomiting (26%), fever
(21%), cough (12%), and nausea(8%).
• Post-operative morbidity was common, but mostly
of mild severity and limited to the first day
Sukhwinder Kaur Bajwa,
and Jasbir Kaur.(2010)
• Keeping in consideration the merits of total intravenous
anesthesia study was conducted to find the ideal drug
combinations which can be used in general anesthesia.
• This study was conducted to evaluate and compare two
drug combinations of TIVA using propofol–ketamine and
propofol–fentanyl and to study the induction, maintenance
and recovery characteristics
• Both propofol–ketamine and propofol–fentanyl
combinations produce rapid, pleasant and safe anesthesia
with only a few untoward side effects and only minor
hemodynamic effects.
A Prasanna et. al. (2010)
• Total intravenous anaesthesia (TIVA) technique is
often not practiced, with the fear of unprotected
airway and possible effect of drugs on foetus.
• This study was designed to verify the safety of
TIVA in cervical cerclage.
• TIVA using Fentanyl and propofol for cervical
cerclage until 16weeks of pregnancy is safe with
no adverse effects on the mother and the foetus.
• It provides early recovery with no pain and Post
operative nausea and vomiting (PONV).
Huseyin S (2012)
• Evaluated the effects of preoperative and
intraoperative administration of intravenous
meperidine as a preemptive analgesic.
• Preoperative meperidine administration shows
superiority to intraoperative administration with
regard to recovery parameters and early
postoperative pain scores
• There were no significant differences between the
groupswith regard to other intraoperative and
postoperative parameters
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