- Acts on GABAa recepotrs in CNS to produce anesthesia - Induction is smooth and rapid - Short duration of action depends on REDISTRIBUTION - Recovery is fast and smooth - Used for induction and maintenance (TIVA): minimal accumulation - No analgesia

- Lipid emulsion=WHITE o Will grow bacteria=discard within 24hrs of opening

- Depression is dose dependent - Myocardial depression - Venodilation=decrease BP - RESETS baroreceptor reflex: increase HR with a drop in BP does NOT occur (only last 10mins) - AVOID in hypovolemic animals and cardiac disease patients

- Reduced capacity for glucuronide conjugation - Propofol infusion=recovery from anesthesia delayed - Repeated administration over several days o Hemolysis and Heinz body formation - can use it on cats still

- Acts on GABAa receptors in CNS - Induction smooth and rapid - Short duration depends on REDISTRIBUTION - Fast recovery (quality improves with premedication) - Used for induction and maintenance (TIVA) - NO analgesia - NO pain or tissue damage

9b – Induction and Injectable Anesthetics Flashcards by Danielle Groenendijk

Propofol

Acts on GABAa recepotrs in CNS to produce anesthesia
Induction is smooth and rapid
Short duration of action depends on REDISTRIBUTION
Recovery is fast and smooth
Used for induction and maintenance (TIVA): minimal accumulation
No analgesia

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Propofol induction is smooth and rapid

Onset 40-90s
One does lasts 5-10mins

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Propofol when injecting: pain/damage

Occasionally pain upon IV injection
NO tissue damage if injected perivascular

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Propofol vehicle

Lipid emulsion=WHITE
o Will grow bacteria=discard within 24hrs of opening

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PropoClear (propofol)

Lipid free formulation

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Propoflo 28 (propofol)

Contains preservative (May be toxic for cats!)
Labelled for use up to 28 days after opening

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Propofol: CV effects

Depression is dose dependent
Myocardial depression
Venodilation=decrease BP
*RESETS baroreceptor reflex: increase HR with a drop in BP does NOT occur (only last 10mins)
AVOID in hypovolemic animals and cardiac disease patients

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Propofol: respiratory system effects

Depression is DOSE dependent
Post: induction apnea and cyanosis
Supplement O2, pre-oxygenate
Mild bronchodilation

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Propofol on induction and/or recovery can occasionally see in dogs

Paddling movements
Opisthotonus
Twitching

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Propofol is recommended for

C-sections
Cerebroprotection: reduces cerebral blood flow and cerebral metabolic rate
Patients with compromised LIVER function

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Propofol in cats

Reduced capacity for glucuronide conjugation
Propofol infusion=recovery from anesthesia delayed
Repeated administration over several days
o Hemolysis and Heinz body formation
*can use it on cats still

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Alfaxalone

Acts on GABAa receptors in CNS
Induction smooth and rapid
Short duration depends on REDISTRIBUTION
Fast recovery (quality improves with premedication)
Used for induction and maintenance (TIVA)
NO analgesia
NO pain or tissue damage

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Alfaxalone: smooth and rapid induction

Onset: 15-45seconds
One dose lasts: 5-10mins

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Alfaxalone vs. Propofol

Longer shelf life (open for 30 days)
Clear solution
Can be administered IM

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Alfaxalone CV effects

Depression Is DOSE dependent
Hypotension: combo of myocardial depression and some peripheral vasodilation
Compensation via reflex tachycardia (baroreceptor reflex)

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Alfaxalone respiratory system affects

Depression is DOSE dependent
Post-induction apnea

Alfaxalone effects

Good muscle relaxation
Produces reliable sedation in cats when give IM
Excellent in reptiles (IM)

Co-induction when using alfaxalone OR propofol to minimize amount required: typical agents included are

Benzodiazepines (Midazolam or Diazepam)
Ketamine

Ketamine

Dissociative anesthetic agent
o Interrupts info reaching higher centers in the brain
Comes in a racemic mixture

How is ketamine different from GABAa agonist drugs?

Cateleptoid state with slow nystagmus
Muscle rigidity with higher doses
Maintains CN reflexes (gag, swallow, palpebral and central eye in dogs and cats)

Ketamine and vet med

Popular
Used for INDUCTION and MAINTENANCE and ANALGESIA
*profound analgesic (somatic>visceral, wind up pain)
Neither anti- or pro-convulsant
*AVOID IN CATS with renal function

Ketamine onset and duration

Onset: 30-90s
Duration: 20-30mins (longer)

Ketamine can be administered

Ketamine: mechanisms of action

NMDA receptor antagonist
CNS voltage dependent Na, K, Ca channels
Depression of CNS acetyl choline receptors
Some action at GABAa receptors
Depression of nociceptive cells in dorsal horn of spinal cord

Ketamine causes muscle rigidity so

- ALWAYS combine with a muscle relaxant (ex. benzodiazepine OR alpha2-agonist)

Ketamine: auditory and visual stimuli distributed during recovery to cause

- Emergence delirium

Ketamine use with other drugs to reduce side effects

- Alpha2 agonists - Benzodiazepines - Acepromazine

CV system: ketamine

- Healthy animals=indirect mild CV stimulation - Sympathomimetic effects for 2-15mins - Increase in cardiac work and myocardial oxygen consumption - AVOID in CATS with hypertrophic cardiomyopathy

CV system: ketamine with critically ill patients OR catecholamine depleted

- May see mild direct myocardial depressant effects

Respiratory system: ketamine

- Minimal respiratory depression - Bronchodilation - Laryngeal and pharyngeal reflexes preserved - Irregular/periodic breathing pattern: apneustic breathing

Behavioural side effects: ketamine

- Can cause rough recoveries o Head shaking, vocalization, dysphoria, salivation

When combining drugs with ketamine the major goals

- Decrease amount of ketamine needed - Eliminate unwanted side effects (improve recovery quality) - Produce good skeletal muscle relaxation - Improve visceral analgesia - Prolong period of anesthesia/immobilization

Ketamine/diazepam (‘Ket-Val’)

- IV induction agent: dogs, cats, neonatal foals, horses, calves, cattle - Slow onset (30-90s) - Short acting, rapid recovery - *MINIMAL CV and respiratory side effects - *do NOT use for C-sections (diazepam accumulates in neonates)

Alpha2 agonist + ketamine examples:

- Xylazine + ketamine - Dexmedetomidine – ketamine – opioid

Xylazine + ketamine

- Good combo for large animals or wildlife immobilization - Analgesia, muscle relaxation, narcosis - Potent cardiopulmonary depression - NOT recommended for routine use in cats and dogs

Dexmedetomidine – ketamine – opioid

- Wildlife, game ranch animals - Supportive care - Monitor closely - Alpha2 reversible

Induction apnea

- Usually observed after rapid bolus of IV induction agent - Once IV induction is redistributed=animal wakes up - Assist ventilation until spontaneous ventilation returns - Once induction agent wears off=inhalant plasma concentration should be enough to keep them anesthetized - Apnea can be avoided by titrating to effect

Apnea or hypoventilation result in

- Poor uptake of maintenance inhalant anesthetic - Poor transition to maintenance phase (stable plane) or inhalant anesthesia

Guaifenesin

- Only used for sedation and muscle relaxant effects