Veterinary Anesthesia
Severna Park Veterinary Hospital
Aug. 6, 2014
Rebecca Krimins, DVM, MS
Advanced Anesthesia and Pain
Management for Animals
Topics
• Anesthetic drugs
• Pre-anesthetic combinations
• Monitoring anesthetic depth
Ketamine
• Dissociative: dissociate the thalamocortic and
limbic systemscataleptoid state (eyes open,
swallow reflex intact)
• Muscle rigidity
• Decreases cardiac contractility
• Increase peripheral vascular resistance
decreases cardiac output
Ketamine
• NMDA-antagonistic properties (blocks
glutamate)
• Helpful with superficial pain, not useful for
deep or chronic pain (poor visceral analgesia)
• Helps prevent sensitization (windup) of
nociceptive pathways
Ketamine
• Rapid onset (~ 5 minutes)
• Moderate DOA (1-2 hours)
• Stimulate sympathetic tone increased HR and
BP
• Induce salivation and airway secretions
• Pain upon IM injection (low pH)
• Some dogs show emergence delirium
(uncoordinated movements of head/neck,
voacalizations, salivation, agitation)
Ketamine Pre-anesthetic Dosage
• Dogs: 1-3 mg/kg IV, IM, SQ
• Cats: 3-10 mg/kg IV, IM, SQ
Ketamine
• CRI dosage for intra-op pain:
– 0.5 mg/kg IV bolus
– 10 ug/kg/min CRI (lower doses for post-op)
• Apnea in some (but generally is NOT a
respiratory depressant)
• Don’t administer with an anticholinergic
• Associated with premature ventricular
depolarizations
Tiletamine
• Dissociative
• More potent than ketamine (3X), longer DOA
• Produces sedation, immobility, amnesia,
analgesia, muscle rigidity
• (Zolazepam: similar to diazepam but is water
soluble and more potent; can cause prolonged
recovery in cats)
Ketamine/valium and
Tiletamine/zolazepam
• Different neuroactive agents usedinduce
anesthesia with the goal of achieving the highest
quality of anesthesia with minimal side effects
• Ketamine/valium
– Ketamine 5 mg/kg IV
– Diazepam 0.25 mg/kg IV
• Tiletamine/zolazepam: (2-8 mg/kg IV, IM)
– DOA: 20 min to one hour
– Limited shelf-life after reconstitution
– Induction: 1-3 mg/kg IV or 6-8 mg/kg IM
Telazol Difference in Dogs vs Cats
• Dogs: get a tiletamine hangover
• Cats: get a zolazepam hangover
Ket/Val (or Telazol) vs Propofol
• Compared to propofol:
– Less muscle relaxation
– Increased salivation
– Increased dysphoria
• Good cardiopulmonary support
– HR, CO, BP well maintained
• Short duration
Propofol
• 2,6,-diisopropylphenol
• Propofol: soybean oil, glycerol, egg
phosphatide
• Propoflo-28: benzyl alcohol
• White emulsion: shake thoroughly (don’t mix
with other drugs)
• Metabolized by liver, extrahepatic sites of
metabolism
Propofol
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Induction dose: 4-8 mg/kg IV
Microdose under GA: 1-2 mg/kg IV
Titrate to effect
Duration of action: 10-20 minutes
Advantages: rapid induction of GA, rapid
metabolism, rapid emergence from GA, low
incidence of nausea/vomiting
Propofol
• Disadvantages
– Hypotension and cardiac depression
– Respiratory depression
– Pain on injection
– Heinz body anemia in cats (repeated use)
Dexmedetomidine
• α-2 adrenergic agonist
• Properties: sedative-hypnotic, analgesic,
muscle relaxation
– Anxiolysis, calming
• Stimulate α2 receptors in braindecreased
norepinephrine release
• Dose-dependent CV effects:
vasoconstrictionhypertensionreflex
bradycardia
Dexmedetomidine
• Dosage: dependent on patient and procedure
– IM: 5 ug/kg
– IV: 1-2 ug/kg
• Rapid onset (~ 5 minutes)
• Moderate duration (~2 hours)
• Atipamezole (reversal):
– Give same volume as dexmedetomidine IM, SQ, IV
Hydromorphone and Morphine
• Pure mu opioids; excellent analgesics
• Both drugs can cause excitement when used
alone, in young, healthy animals
• Both drugs will slow heart rate (increased
vagal efferent activity) and cause respiratory
depression
• Profound sparing effect with induction and
maintenance agents
Hydromorphone vs Morphine
• Hydromorphone:
– SQ route associated with vomiting & panting
– Doses > 0.1 mg/kg may produce hyperthermia
– DOA: 1-4 hours
• Morphine:
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Can cause vomiting
Associated with histamine release
Excitement in cats
Metabolites excreted by the kidneys
DOA: 2-4 hours
• Pupil size: miosis and mydriasis
– Miosis (dogs)
– Mydriasis (cats)
Hydromorphone and Morphine
• Hydromorphone dosages (SQ, IM, IV)
– SQ: 0.1 mg/kg (DOA: 1-4 hours)
– IV: 0.05 mg/kg (DOA: 1-2 hours)
• Morphine (SQ, IM, IV)
– IM: 0.2-0.6 mg/kg
– IV: 0.1-0.5 mg/kg
• Naloxone (reversal) 1-10 ug/kg IV
– Take 1 ml naloxone, dilute with 9ml saline, titrate
1 ml/min to effect
Pre-anesthetic Combinations
• Think about:
– Procedure: surgical vs diagnostic vs other
– Level of pain involved in procedure
– Duration of procedure
– Patient status
– How much time do you have
Pre-anesthetic Combinations
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Opioid
+/- benzodiazepine
+/- α2- agonist
+/- phenothiazine
+/- anticholinergic
How to Monitor Anesthetic Depth
• No single parameter tells you how light/deep
– Gather all information together (patient, normals,
disease states, drugs, procedure type and
duration)
• Must know parameter normals in order to be
able to identify abnormals
– Temp, pulse, RR, BP
– SBP > 140 mmHg = light
– SBP < 80 mmHg = deep
How to Monitor Anesthetic Depth
• Interact with patient
• Every 5 minutes, check palpebral reflex
(corneal reflex) and jaw tone; position of eye;
check for signs of movement, muscle
twitching, neck tone
• Maintain body temperature
• Vaporizer setting for past 15 minutes = ?
Questions
Email: drkrimins@gmail.com
Advanced Anesthesia and Pain Management
for Animals
www.aapma.com