Veterinary AnesthesiaSeverna Park Veterinary Hospital

Aug. 6, 2014

Rebecca Krimins, DVM, MSAdvanced Anesthesia and Pain

Management for Animals

Topics

• Anesthetic drugs• Pre-anesthetic combinations• Monitoring anesthetic depth

Ketamine

• Dissociative: dissociate the thalamocortic and limbic systemscataleptoid 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 andTiletamine/zolazepam

• Different neuroactive agents usedinduce 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

• 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 braindecreased norepinephrine release

• Dose-dependent CV effects: vasoconstrictionhypertensionreflex 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:– 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

• 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 Managementfor Animals

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