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Pharmacology > Sedation 1 > Flashcards

Sedation 1 Flashcards

1
Q

why do we use chemical restraint (6)

A

-To control dangerous/uncooperative patients
-For minor diagnostic/surgical procedures
-Prior to anesthesia
-To control intra-op & post-op pain
-To smooth recovery
-To facilitate post-op treatments

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2
Q

three categories of chemical restraint

A

tranquilizers/sedatives, aesthetics, opiods

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3
Q

types of sedatives (3)

A

phenothiazines, alpha-2 agonists, benzodiazepines

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4
Q

what is a big caution to be aware of when using IV CNS depressants

A

Accidental injection into carotid artery may be fatal!!!

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5
Q

common properties of most sedatives (2)

A

1) Reduction of induction dose & MAC reduction
-Sedated patients require lower dosages of induction agent (depends on dose, but often on the order of HALF the dose that would be required to induce an un-premedicated patient), and may require lower dosages of inhalant anesthetic, compared to un-premedicated patients

2) Improved quality of recovery from general anesthesia
-Sedatives allow patients to experience a smoother recovery from general anesthetics

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6
Q

what is the main phenothiazine

A

acepromazine

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7
Q

what does acepromazine do

A

A major tranquillizer & sedative!!
-Reduces fear & anxiety  calms patient
-Reduces response to stimuli
-Induces lethargy
-Relaxes muscles

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8
Q

main use of acepromazine

A

restraint

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9
Q

time to clinical effect of acepromazine

A

15 min (IV)
30 min (IM)
60 min (oral)

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10
Q

what is required for fast onset of most sedatives

A

a quiet environment

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11
Q

mechanism of action for phenothiazines

A

Blocks dopamine D2 receptors in brain
-Dopamine is needed for wakefulness & motor activity
-Excessive D2 stimulation = schizophrenia
-D2 blockade = sedation, reduced anxiety

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12
Q

what is the reason for side effects when using phenothiazines

A

Unfortunately, phenothiazines also block other receptors, especially peripheral α1 = side effects

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13
Q

what happens when phenothiazines block alpha 1 receptors

A

causes vasodilation and sphincter
relaxation = side effects

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14
Q

what are alpha1 receptors normally doing in terms of vessels and GIT/bladder

A

stimulated by NE causes vasoconstriction

α1 stimulation by NE also causes constriction of G.I. & urinary tract sphincters

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15
Q

what is the overall main adverse effect of phenothiazines and another specific to ruminants

A

-Peripheral α1 blockade = vasodilation = hypotension (MAIN)

-Ruminants: regurgitation due to relaxed cardiac sphincter

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16
Q

what is an adverse effect of acepromazine in male horses

A

-Retractor penis muscles are adrenergic
-Penile prolapse occurs, even with low doses
-Intensity of effect varies widely from horse to horse
-Dose-dependent duration, can last 1-2 hours = edema = constriction of blood supply = ischemic necrosis
= amputation required in worst cases

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17
Q

cautions to take with acepromazine in male horses

A

-Use with caution (or avoid), esp. in breeding stallions
-Do not use in male horses (intact or not) with prior episode of prolonged protrusion following acepromazine admin.

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18
Q

contraindications of phenothiazines (6)

A

-Hypovolemic/shocky patients
-Valuable breeding stallions? Or use with caution and monitor?
-Unattended animals (esp. large animals: injury during onset)
-Organophosphate poisoning
-OPs cause cholinergic PSNS overstimulation
-Phenothiazines inhibit ACh esterase
-Even OP-containing flea collars are a label contraindication
-Herding breeds with p-gp/MDR1 mutations are more sensitive (e.g., Collies, Australian Shepherds, Whippets, others)
-Some Boxer families appear to be esp. sensitive to cardiac effects (syncope & collapse) so to be safe acepromazine should be avoided in this breed

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19
Q

what is an example of a butyrophenone

A

azaperone

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20
Q

what species is azaperone used for and why

A

pigs - Used because it has a 1-day
meat withdrawal time in swine, vs 7 days for acepromazine

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21
Q

what are four alpha-2 agonists

A

-Xylazine
-Detomidine
-Dexmedetomidine
-Romifidine

22
Q

anagelsia vs sedation of xylazine

A

-sedation lasts 2h
-analgesia is excellent but it only last 30 minutes

23
Q

mechanism of action of alpha-2 agonists and specific changes that occur

A

α2 stim. opens K+ channels = inhibits APs in brain pathways related to:
* Wakefulness (= sedation)
* Pain (= analgesia)
* BP control (= hypotension)
* Motor activity (= muscle relaxation)
* Respiration: may be dramatic drop in O2 exchange

-overall In the brain, pre-synaptic alpha-2a stimulation opens K+ channels = inhibits NT release in various brain pathways

24
Q

mechanism of adverse effects of alpha-2 agonists

A

-Side effect: Transient vasoconstriction

-Alpha-2 agonists also stimulate peripheral alpha 1 & alpha 2b receptors on blood vessels to some extent = initially see vasoconstriction & increased BP

-A slower activation of pre-synaptic alpha 2a receptors in ganglia then inhibits NT release, which inhibits SNS outflow = subsequent drop in BP

25
Q

potential adverse effects of alpha-2 agonists in large animals

A

-vasoconstriction (stim. of α1 and α2b R on blood vessels) = initial rise in
BP, then see bradycardia due to slower central α2 stim. which inhibits SNS outflow = potential for hypotension (a potentially serious effect)

-Significant muscle relaxation (most animals lie down, which may be a benefit)

26
Q

what happens in cast 2-5minutes after administration of an alpha-2 agonist

A

they will vomit

27
Q

how do you reverse alpha 2 agonists

A

Can reverse with α2 antagonists

28
Q

two possible issues that can occur when giving alpha-2 agonists to dogs or small ruminants/calves/sick cattle

A

-Decreased GI motility = bloat (large dogs)

-Degranulation of pulmonary intravascular macrophages in ruminants = May kill small ruminants, calves, sick cows via pulmonary edema

29
Q

are xylazines normally used in small or large animals

A

usually large, only a few uses in small animals

30
Q

what do you need to remember about sensitivity in large animals

A

Many domestic ruminants are highly sensitive; Possess an alpha-2D receptor that other species lack
= require only 1/10th the dose of other species

31
Q

main uses of xylazine in large animals

A
  • Alone = restraint
  • With ketamine = general anesthesia
  • With opioid = short surgical procedure
  • Epidural analgesia (horses)
  • Has been used with acepromazine for heavy sedation
32
Q

what species is demotidine approved in

A

horses

33
Q

features of demotidine in horses

A
  • Analgesia is thought to last as long as sedation (1-2 h)
  • Animals may kick even when fully sedated
  • If light, can top up with guaifenesin or add opioid, rather than using more detomidine (animal may be resistant or agitated)
  • Peak sedation in 5-20 min
  • Used when pain greater, or longer effect desired
34
Q

what is the main difference between xylazine and demotidine

A

duration of action

35
Q

what species is dexmedetomidine approved in

A

dogs and cats

36
Q

what is the most popular alpha 2 agonist is small animal practice

A

dexmedetomidine

37
Q

what species is romifidine used in and why

A

horses

-50% longer sedation than xylazine (0.5 – 3 h, depending on dose) & less head droop and ataxia than equipotent doses of xylazine or detomidine = helpful for dentistry

38
Q

what are two alpha 2 antagonists

A

Atipamezole, yohimbine

39
Q

specificity of atipamezole

A

Atipamezole is more specific for α2 vs. α1

40
Q

what could happen if you dont titrate a2 antagonists

A

Titrate to effect – don’t be overzealous or may cause increased
SNS effects and pain

41
Q

what is the main benzodiazepine

A

diazepam

42
Q

what is diazepam used for

A

Sedative, muscle relaxant, & anticonvulsant

43
Q

mechanism of action of benzodiazepines

A

-Inhibits APs in post-synaptic cells by facilitating the action of GABA at the GABAa receptor (the main inhibitory NT in brain)

-GABAa receptors are a type of ligand-gated chloride channel = open in response to binding of GABA = hyperpolarizes cell= inhibits excitation

44
Q

why are benzos safe when used alone

A

because little effect on CV system

45
Q

how can you reverse benzo overdose effects

A

Overdose effects can be reversed by flumazenil, a competitive inhibitor of the BZD binding site

46
Q

what is an effective appetite stimulant in cats

A

benzos

47
Q

what can happen with hepatic function in cats when giving benzos

A

Cats: fulminant hepatic necrosis (lethargy, jaundice +/- death); idiosyncratic; may follow >2 days admin.

48
Q

what is a dose dependent side effect of benzos

A

Dose-dependent respiratory depression

49
Q

why is midazolam used instead of diazepam

A

Midazolam is similar but water soluble, so better for IM use when rapid effect is desired (also shorter T1/2)

50
Q

what is a common induction mixture in small animal medicine

A

A 1:1 mixture of diazepam:ketamine is a very common induction mixture in small animal medicine

51
Q

what is a problem that might be seen in small animals and horses with benzo use

A

Excitement & paradoxical aggression problems in healthy small animals & horses = administered in combination with other drugs

52
Q

what is guaifenesin used for and in what species? how does it act?

A

-A muscle relaxant (sedation occurs only at high doses)
-Used in horses at induction to relax muscles to help a sedated horse go down smoothly
-Acts centrally: inhibits excitatory interneurons in motor pathways

Pharmacology (16 decks)

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