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Module 14 > Clinical Pharmacology of Anesthetics > Flashcards

Clinical Pharmacology of Anesthetics Flashcards

1
Q

what are the injectable anesthetics used in vet med (5)

A
  1. propofol
  2. steroid anesthetics: alfaxalone
  3. barbiturates: thiopentone, pentobarbitone
  4. imidazole derivatives: etomidate
  5. dissociative agents: ketamine, tiletamine (+ zolazepam = zoletil)
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2
Q

what is the onset of propofol

A

rapid

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3
Q

what is the duration of propofol

A

short duration IV anesthetic

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4
Q

what is the structure of propofol

A

hindered phenol

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5
Q

what is the mechanism of propofol

A

potentiates GABA

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6
Q

what is the formulation of propofol

A

oil in water emulsion

soyabean oil, egg lecithin & glycerol

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7
Q

what is the route of administration of propofol

A

IV

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8
Q

what are the pharmacokinetics of propofol

A

highly protein bound

rapid metabolism in liver + lungs, kidneys, blood?

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9
Q

what is the recovery from propofol initially from

A

due to redistribution

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10
Q

do cats or dogs have a more rapid metabolism of propofol

A

slower in cats because less able to conjugate with glucuronide –> avoid IV infusions

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11
Q

what are the effects of propofol on the CNS (3)

A
  1. rapid loss of consciousness (~5 min)
  2. reduced intracranial pressure (ICP)
  3. anticonvulsant action
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12
Q

what are the effects of propofol on the CVS (2)

A
  1. vasodilation & transient fall in BP
  2. mild myocardial depression at high doses
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13
Q

what are the effects of propofol on respiratory system

A
  1. post-induction apnea
  2. occasional cyanosis at induction
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14
Q

what other effects can propofol have

A
  1. pain on injection?
  2. occasional muscle twitching/hypertonus
  3. heinz body anemia in cats (oxidative damage to RBCs)
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15
Q

what is propofol licensed for

A

IV admin in dogs and cats

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16
Q

what are the uses of propofol

A
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17
Q

what is propofol use cautioned in (3)

A
  1. shocked/hypovolemic patients
  2. cats with hepatic dysfunction
  3. cats requiring repeat anesthetics
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18
Q

what are the 2 formulations of propofol

A
  1. preservative free: in use shelf life 6 hours
  2. with preservative: propofol plus with benzyl alcohol
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19
Q

what is the propofol with preservatives contraindicated for

A

prolonged infusion (>30 mins)

dont give >24mg/kg per anesthetic

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20
Q

what is the structure of alfaxalone

A

steroid anesthetic

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21
Q

what is the mechanism of alfaxalone

A

potentiates GABA

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22
Q

what is the formulation of alfaxalone

A

solubilized in cyclodextrin

some have preservatives

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23
Q

what is alfaxalone

A

rapid onset, short duration injectable anesthetic with high therapeutic index

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24
Q

what are the admin routes for alfaxalone

A

IV (IM & SC)

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25
Q

how is the protein binding of alfaxalone vs propofol

A

lower protein binding

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26
Q

what is the recovery from alfaxalone initially due to

A

redistribution

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27
Q

how is alfaxalone metabolized

A

liver

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28
Q

is alfaxalone suitable for TIVA in dogs and cats

A

yes

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29
Q

what are the effects of alfaxalone on CNS

A

rapid loss of consciousness

30
Q

what are the effects of alfaxalone on the CVS

A

mild hypotension at clinical doses, primarily due to vasodilation

31
Q

what are the effects of alfaxalone on respiratory system

A

post-induction apnea (less frequent compared to propofol)

32
Q

how is the recovery from alfaxalone

A

can be poor quality, esp if limited/poor premedication

33
Q

what is the clinical use of alfaxalone

A
  1. admin IV to induce anesthesia
  2. admin IV (intermittent bolus or continuous infusion) to maintain anethesia in dogs & cats
  3. IM/SC for sedation (not authorized, large volume of injection)
34
Q

what is ketamine

A

dissociative anesthetic and analgesic

35
Q

what is the mechanism of ketamine

A

NMDA receptor antagonist

36
Q

what is the formulation of ketamine

A

acidic pH

37
Q

what are the pharmacokinetics of ketamine

A

rapid hepatic metabolism

38
Q

what are the routes of admin of ketamine

A

IV, IM, SC

39
Q

which species is TIVA ketamine suitable for

A

horses

40
Q

what effects do dissociative anesthesia ketamine cause (5)

A
  1. sensory loss with analgesia
  2. increased muscle tone
  3. eyes open +/- slow nystagmus
  4. active relfexes including laryngeal/pharyngeal reflexes
  5. less profound CVS & resp depression
41
Q

what are the effects of ketamine on the CNS (4)

A
  1. loss of consciousness with analgesia
  2. increased ICP
  3. convulsions in dogs/horses (esp if used as sole agent)
  4. hallucinations/emergence delirium
42
Q

what are the effects ketamine has on the musculoskeletal system

A

increased muscle tone

43
Q

what are the effects ketamine has on the CVS

A
  1. in vitro direct -ve inotropic effect
  2. in vivo increased sympathetic tone –> increased HR, contractility, CO & BP
44
Q

what are the effects of ketamine on the respiratory system (2)

A
  1. transient apnea possible with IV admin (ventilation usually well maintained when given by SC or IM)
  2. laryngeal and pharyngeal relfexes maintained?
45
Q

what are the clinical uses of ketamine (3)

A
  1. to induce anesthesia in dogs, cats, horses + combine with benzodiazepams & injected IV
  2. to induce anesthesia & maintain anesthesia (~30 mins) in dogs and cats + a2 agonist and butorphanol & injected IM (“triple combo”)
  3. to provide analgesia in dogs and cats (lower dose IM or IV)
46
Q

what are the cautions of ketamine (3)

A
  1. elavated intracranial pressure
  2. history of seizures
  3. pre-existing tachycardia
47
Q

when might you use TIVA

A
  1. where inhalational agents not available
  2. where airway cannot be shared (bronchoscopy, some airway surgeries)
48
Q

what are examples of TIVA in dogs

A

propofol or alfaxalone are suitable

poor reflex suppression so can combine with analgesics

49
Q

what are TIVA examples in cats

A

only alfaxalone suitable

50
Q

what are examples of TIVA in horses

A

triple drip

alpha2 agonist plus GGE plus ketamine

field anesthesia

51
Q

how do you select the right agent

A

little to chose between propofol, alfaxalone

52
Q

when would ketamine be used

A
  1. IM anesthesia required –> aggressive patient, no IV access, no facilities for delivering inhaled agents
  2. hemodynamic instability is present
53
Q

what would reduce CVS depression in cases with hemodynamic instability

A

co-induction

54
Q

how is anesthesia maintained

A
  1. TIVA or IM triple combo
  2. inhalational agents
55
Q

what are the advantages of inhalational anesthetic agents

A

delivery/elimination depends on ventilation –> rapid adjustment of anesthetic depth

56
Q

what are the disdvantages of inhalational anesthetic agents (2)

A
  1. equipment required: ET tube, carrier gas, vaporizer, breathing system
  2. environmental pollution
57
Q

what are inhalational agents

A
  1. isoflurane
  2. sevoflurane
58
Q

what is the minimum alveolar concentration

A

steady state minimum alveolar concentration of anesthetic required to prevent gross purposeful movement in response to noxious stimulation in 50% of test subjects

compares the potency of different inhaled anesthetics

59
Q

which is more potent isoflurane or sevoflurane

A

sevoflurane more potent (higher MAC)

60
Q

what is the oil:gas partition coefficient

A

measure lipid solubility

high oil:gas PC confers high potency

61
Q

what is the blood:gas partition coefficient

A

measures solubility in the blood

low blood solubility confers to rapid onset, recovery & rate of change of anesthetic depth

62
Q

which has a higher blood:gas coefficient between isoflurane and sevoflurane

A

isoflurane

63
Q

how are inhalational agents metabolized and eliminated

A

exhalation

liver metabolism

can produce toxic metabolites

64
Q

compare the differences of isoflurane and sevoflurane (MAC, oil:gas, blood:gas coefficient, metabolism)

A
65
Q

what are the effects of isoflurane and sevoflurane on the CVS (2)

A
  1. hypotension: CO maintained (except deep plane) and peripheral vascular resistance falls
  2. no sensitization to catecholamines
66
Q

what are the effects of isoflurane and sevoflurane on the resp system

A
  1. depression: reduced rate

sevo causes less depression

67
Q

what are the effects of desoflurane on CVS and resp rate

A

CVS: rapid increases in inspired concentration can increase heart rate and arterial BP (catecholamines)

resp: high inspired concentration can cause airway irritation

68
Q

which agents have the highest onset

A

isoflurane > sevoflurane > desflurane

69
Q

which agents can be used for mask induction

A

sevoflurane is the only one that has a pleasant odour

70
Q

which agent has the least airway irritation

A

desflurane > isoflurane > sevoflurane

71
Q

compare the authorization, potency, rate of change of depth, mask induction, metabolism and cost of isoflurane, sevoflurane, desflurane

A
72
Q

what is nitrous oxide

A

weak anesthetic and weak analgesic

Module 14 (29 decks)

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