Equine Field Anesthesia: The Drugs

Question 1

what are the categories of drugs

Answer 1

1. tranquilizers: phenothiazines, butyrophenones
2. alpha 2 agonists
3. benzodiazepines

Question 2

what class of drug is acepromazine

Answer 2

phenothiazine

Question 3

what is the effect of acepromazine

Answer 3

1. calming
2. indifference
3. decreased locomotor activity

Question 4

what is the mechanism of action of acepromazine

Answer 4

1. dopamine D1 and D2
2. a2
3. muscarinic
4. serotnergic
5. histamine

Question 5

how is acepromazine administered

Answer 5

injectable and PO

Question 6

what is the time to peak effect after acepromazine administration

Answer 6

IV: 20 min

IM: 45-60 min

Question 7

what drugs does acepromazine act synergistically with

Answer 7

a2 agonists and opioids for analgesia and CNS depression

Question 8

what is the effect of acepromazine and opioid combo

Answer 8

acepromazine may counteract opioid excitability

Question 9

how does acepromazine reduce mortaility in GA (4)

Answer 9

1. antiarrhythmic
2. vasodilation –> perfusion increases
3. anesthetic requirements decreased
4. smoother recovery

Question 10

what are the disadvantages of acepromazine (5)

Answer 10

1. no reliable sedation
2. no analgesia
3. long duration of action (4-6 hours)
4. no antagonist
5. not licensed or in table 1 for farm animals

Question 11

what are the adverse effects of acepromazine (4)

Answer 11

1. vasodilation –> hypotension
2. seizure threshold decreases
3. priapism
4. may increase risk of of regurgitation

Question 12

what are the contraindication of acepromazine (3)

Answer 12

1. pre-exisiting hypotension
2. history of seizures
3. breeding stallions

Question 13

what are alpha 2 agonists

Answer 13

sedative

Question 14

do alpha 2 agonists have analgesia

Answer 14

yes

Question 15

do alpha 2 agonists offer reliable sedation in horses

Answer 15

yes

Question 16

what are the effects of alpha 2 agonists

Answer 16

1. resp: upper airway obstruction
2. CV: bradycardia, initial hypertension, arrhythmogenicity
3. others: decreased GI motility, diuresis, sweating, muscle relaxation

Question 17

what are the alpha 2 agonists and their concentration, volume required, duration of action, standing chemical restraint (yes/no), routes of administration, species

Answer 17

Question 18

what is the benzodiazepine mechanism of action

Answer 18

GABA_A receptor agonist

Question 19

what are benzodiazepine used for

Answer 19

sedatives and adjunct anesthetic drugs

Question 20

what are examples of benzodiazepine

Answer 20

midazolam and diazepam

Question 21

can benzodiazepine be used in foals

Answer 21

yes < 4 weeks

Question 22

what are the effects and side effects of benzodiazepine (6)

Answer 22

1. CNS: sedation, anesthetic sparing effect, anticonvulsive action
2. resp: depression
3. minimal effects at clinically relevent doses
4. muscle relaxation
5. counteracts muscle rigidity caused by ketamine
6. ataxia after prolonged infusion in horses

Question 23

what opioid is allowed in food producing animals

Answer 23

butorphanol

Question 24

what are the opioids and the licensing, receptor action, administration, duration of action, sedative action, species

Answer 24

Question 25

what are the opioids side effects in horses (4)

Answer 25

1. CNS: locomotion, dysphoria 2. resp: minimal effects at clinically relevant doses, increase resp rate (alone), potentiation of resp depression (with alpha 2 agonists) 3. CV: minimal effects, opioids alone heart rate and BP increased, when combined with a2 agonists tend to predominate 4. histamine release: morphine + pethidine

Question 26

what are the actions of NSAIDs

Answer 26

1. anti-inflammatory 2. anti-pyretic 3. analgesia

Question 27

what are the anesthetic induction drugs (5)

Answer 27

1. ketamine 2. thiopentone 3. propofol 4. alfaxalone 5. guaifenesin

Question 28

what effect does ketamine have

Answer 28

1. dissociative anesthetic 2. analgesic (skin and musculoskeletal pain, poor for visceral pain)

Question 29

what mechanism of action does ketamine use

Answer 29

NMDA antagonist

Question 30

what is ketamine used for (4)

Answer 30

1. sedation in pigs and cattle 2. induction 3. anesthetic maintenance 4. post operative analgesia

Question 31

what is ketamine combined with for induction

Answer 31

benzodiazepines or guaifenesin +/- thiopentone in food producing animals

Question 32

how is ketamine used for anesthetic maintanence

Answer 32

+/- muscle relaxant and/or alpha 2 agonist emergency top up drug in horses

Question 33

what are the effects and side effects of ketamine

Answer 33

Question 34

what is thiopentone

Answer 34

short acting barbiturate GABA_A receptor agonist

Question 35

what is the onset and duration of thiopentone

Answer 35

fast onset (30s) and short duration (\<10 min)

Question 36

does thiopentone provide analgesia

Answer 36

no

Question 37

is thiopentone licensed

Answer 37

no

Question 38

what are the uses of thiopentinone

Answer 38

emergency top up in horses

Question 39

what are the side effects of thiopentone

Answer 39

Question 40

what is guaifenesin

Answer 40

centrally acting muscle relaxant

Question 41

does guaifenesin provide analgesia

Answer 41

no

Question 42

how is guaifenesin administered

Answer 42

infused IV to effect or as part of triple drip

Question 43

what are the effects and side effects of guaifenesin

Answer 43

Question 44

how does propofol act

Answer 44

GABA_A agonist

Question 45

what is propofol used

Answer 45

1. anesthetic induction 2. anesthetic maintenance

Question 46

what is alfaxalone

Answer 46

GABA_A agonist

Question 47

what is alfaxalone used for

Answer 47

1. induction 2. sedation in pigs (IM) in combo with opioid and midazolam

Question 48

what are the effects on recovery in horses of alfaxalone

Answer 48

poor recoveries