Pre-anesthetic drugs

Question 1

what are pre-anesthetic drugs used for?

Answer 1

tranquilize or sedate which lowers patient stress and facilitate handling, decrease the dose of maintenance drugs, allow smoother induction and recovery, used for analgesia, prevents adverse effects

Question 2

sedation

Answer 2

CNS depression, drowsiness, drug-induced, various levels, slightly aware or unaware of surroundings, aroused by noxious stimulation
used for minor procedures

Question 3

tranquilization

Answer 3

calmness, relaxation, reduced anxiety, not drowsiness, patient reluctant to move, aware of surroundings but doesn’t care

Question 4

Phenothiazines

Answer 4

Chlorpromazine - antiemetic
acepromazine
used as an adjunct in pre-med with opioids or as a tranquilizer by itself
non-controlled
approved for use in dogs, cats, horses
used for simple procedures, anxiety, and as a tranquilizer

Question 5

Acepromazine

Answer 5

Phenothiazine
causes depression, has antiemetic properties, peripheral vasodilation, heat loss, tachycardia, decreases CO, protects against ventricular arrhythmias, antihistamine

Question 6

Acepromazine mode of action

Answer 6

depression of reticular activating center of brain, blockade of alpha-adrenergic dopamine and histamine receptors, metabolized in liver, crosses placental barrier

Question 7

Acepromazine onset of action, peak effect, duration, and dosage

Answer 7

onset of action: 15 min
peak effect: 30-60 min
duration: 4-8 hours, up to 48 hours in sick patients
dosage: 0.05-0.1 mg/kg in dogs and cats, 0.03-0.05 mg/kg in horses

Question 8

Benzodiazepines

Answer 8

Diazepam, Midazolam, Zolazepam
used for muscle relaxation, immediate seizure treatment, appetite stimulant, behavior modification
often used with adjuncts
reversible
C-IV controlled
crosses placenta
may use as a CRI (great MAC reducer)
IM, IV, po

Question 9

Diazepam

Answer 9

Benzodiazepine
oil based (propylene glycol) (IV slow)
not water based, okay to use with ketamine
causes antianxiety and calming effects, HP/BP/RR minimally affected, appetite stimulation, muscle relaxation

Question 10

Diazepam mode of action

Answer 10

depress CNS, enhances effects of neurotransmitters in gamma-aminobutyric acids (GABA), exact mechanism unknown

Question 11

Diazepam onset of action, duration, reversal

Answer 11

onset of action: 15 min IM, 1-2 min IV
duration: 1-4 hours
may be reversed with Benzodiazepine antagonist
ceiling effect
hemolysis of RBC

Question 12

Benzodiazpine antagonist

Answer 12

Flumazenil: expensive, light sensitive, competitive in GABA receptors

Question 13

Alpha2-andrenoceptor agonists

Answer 13

IV, IM, po
Dexmedetomidine (Dexdomitor), Medetomidine, and Xylazine
used for sedation in minor procedures, analgesia, muscle relaxation
often used with adjuncts
non-controlled
reversible
causes sedation, some analgesia, vasoconstriction/hypertension/reflex bradycardia/pale mm/cardiac arrhythmias and heart blocks at first then decreased CO/hypotension/continued bradycardia due to decreased sympathetic tone and decreased RR/Vt

Question 14

Alpha2-andrenoceptor agonist mode of action

Answer 14

acts on alpha2-adrenergic receptors of the sympathetic nervous system in PNS and CNS causing a decrease in the release of neurotransmitter norepinephrine

Question 15

Alpha2-andrenoceptor other effects and onset of action

Answer 15

onset of action: > 10 min IM, ~1-3 min IV, ~15 min po
other effects: excitability, vomiting (cats), hyperglycemia, hypothermia

Question 16

alpha2-antagonist

Answer 16

IM, never IV
Atipamezole reverses Dexmedetomidine
Yohimbine reverses Xylazine
mode of action: displaces A2 agonist from receptor, affinity to the antagonist
may cause adverse effects on the neurological, CV, and GI systems
may also cause muscle tremors, hypotension, tachycardia, salivation, and diarrhea
don’t give with anticholinergics or in absence of an agonist

Question 17

Anticholinergics

Answer 17

SQ, IM, IV
block parasympathetic nervous system which blocks SLUDDE
dilates pupils, increases HR by preventing bradycardia, decreases secretions of respiratory tract, decreases GI motility and bladder contractions

Question 18

Atropine

Answer 18

anticholinergic
fast onset, short duration, crosses blood brain barrier, crosses placenta
antidote for organophosphate toxicosis
best for ER use