Veterinary Anesthesia Severna Park Veterinary Hospital Aug. 6, 2014

1. Veterinary AnesthesiaSeverna Park Veterinary HospitalAug. 6, 2014 Rebecca Krimins, DVM, MS Advanced Anesthesia and Pain Management for Animals

2. Topics • Anesthetic drugs • Pre-anesthetic combinations • Monitoring anesthetic depth

3. 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

4. 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

5. 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)

6. Ketamine Pre-anesthetic Dosage • Dogs: 1-3 mg/kg IV, IM, SQ • Cats: 3-10 mg/kg IV, IM, SQ

7. 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

8. 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)

9. Ketamine/valium andTiletamine/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

10. Telazol Difference in Dogs vs Cats • Dogs: get a tiletamine hangover • Cats: get a zolazepam hangover

11. Ket/Val (or Telazol) vsPropofol • Compared to propofol: • Less muscle relaxation • Increased salivation • Increased dysphoria • Good cardiopulmonary support • HR, CO, BP well maintained • Short duration

12. 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

13. 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

14. Propofol • Disadvantages • Hypotension and cardiac depression • Respiratory depression • Pain on injection • Heinz body anemia in cats (repeated use)

15. 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reflexbradycardia

16. 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

17. HydromorphoneandMorphine • 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

18. Hydromorphonevs 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)

19. 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

20. 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

21. Pre-anesthetic Combinations • Opioid • +/- benzodiazepine • +/- α2- agonist • +/- phenothiazine • +/- anticholinergic

22. 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

23. 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 = ?

25. Questions Email: drkrimins@gmail.com Advanced Anesthesia and Pain Management for Animals www.aapma.com