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Anesthesia > Sedatives > Flashcards

Sedatives Flashcards

1
Q

Why use premedication?

A

-relieve anxiety and stress in patient
-to smooth induction of anesthesia, maintenance phase of anesthesia, recovery from anesthesia
-Anesthetic sparing (reduce dose of induction and maintenance anesthetic agents and therefore reduce side effects)
-provide analgesia
-reduce muscle tone

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2
Q

Factors of an ideal premedication

A

-relieve fear and anxiety
-easily administered
-quick onset of action
-reasonable duration of action
-reversible
-predictable (dose)
-safe
-minimal side effects (cardio, resp)
-provide analgesia, muscle relaxation
-possibly provide amnesia

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3
Q

Pre-anesthetic medications

A

-Phenothiazines
-Butyrophenones
-alpha 2 agonists
- benzodiazepines- in some animals
-anticholinergics
-opioids
-ketamine

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4
Q

Phenothiazines, Butyrophenones, alpha 2 agonists, benzodiazepines (in some animals)

A
  • sedation to calm animal and reduce anxiety
    -anesthetic sparing effect
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5
Q

Anticholinergics

A

-prevent undesirable side effects (bradycardia)

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6
Q

Opioids, alpha 2 agonists, ketamine

A

-provide analgesia (pre-emptively)

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7
Q

Phenothiazines actions

A

-anti-adrenergic (alpha 1 block)
-antidopaminergic
-anticholinergic (muscarinic block)
-antihistaminic (H1 block)
-antiserotonergic (serotonin block)
-local anesthetic effects (clock ion channels)
-anti-arrhythmic
-no analgesia
-antithrombotic actions

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8
Q

Phenothiazines effects

A

-sedation
-hypotension
-hypothermia
-anti-emetic
-anti-arrhythmic

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9
Q

Phenothiazines chemical structure

A

-contain two benzene rings that are linked by a sulphur and nitrogen atom
-highly protein bound (more than 90%)
-lipophilic
-hepatic metabolism

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10
Q

Phenothiazines homeostasis control

A

-vasomotor control
-thermoregulation
-hormonal balance
-acid-base balance
-emesis

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11
Q

Phenothiazines mechanism of action

A

-Mediated by antidopaminergic actions in CNS (post-synaptic DA receptor blockage results in inhibition of dopamine release)
-results in mental calming effect

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12
Q

Overdose of phenothiazines

A

increased extra-pyramidal signs

**1mg is max dose ever

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13
Q

Phenothiazines cardio effects

A

Hypotension through vascular smooth muscle alpha 1 receptors
-not reversible
-duration is dose dependent (can last 8hrs)
-supportive management (fluid therapy and pressure support)

**avoid in volume depleted animals or when hemorrhage present

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14
Q

Phenothiazines respiratory effect

A

-reduce the sensitivity of the respiratory center to CO2
-slight reduction in RR
**overall, no change in blood gas

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15
Q

Phenothiazines thermoregulatory effect

A

Hypothermia can occur due to disruption of thermoregulation and cutaneous vasodilation

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16
Q

Phenothiazines anti-emetic effect

A

-positive; effects central chemoreceptor trigger zone

**effectiveness against opioids- need to give 15-20 mins prior

17
Q

Phenothiazines anti-arrhythmic effect

A

-positive
-increases the concentration of EPI required to induce cardiac arrhythmias

18
Q

Acepromazine (phenothiazine)

A

-common in vet med (cats, dogs, horses, rare in ruminants and exotics)
-30-40% anesthetic sparing
-mild sedation when used alone, no analgesia
-can be used in seizure animals
-can be used to control emergence delirium during recovery from anesthesia
-solution is yellow
-slow time to onset of effect
-dose dependent (duration and side effects)

19
Q

What is Acepromazine (phenothiazine) given with commonly?

A

alpha 2 agonists, opioids

20
Q

Acepromazine (phenothiazine) in horses

A

sometimes linked to penile prolapse
-will effect future breeding so avoid in stallions!

21
Q

Benzodiazepines

A

-anticonvulsant, reduce amount of major anesthetic (anesthetic sparing), muscle relaxant
-avoid using alone in dogs, cats, horses because can cause excitement or aggressiveness
-combine with mu-opioids (IV or IM)
-good for very young, old, and very sick
-exotics
-no analgesia
-retrograde amnesia

22
Q

Benzodiaepines chemical structure

A

-benzene rings fused to diazepine ring
- highly protein bound

23
Q

Benzodiaepines absorption

A

-hepatic metabolism (oxidation and conjugation)
-well absorbed across mucous membrane
-significant first-pass metabolism= so need to increase dose

24
Q

Benzodiaepines mechanism of action

A

Acts on specific benzodiazepine binding sites which are associated with GABA A Receptors. This enhances the affinity for and action of GABA (inhibitory neurotransmitter)

Results in depressed activity in reticular activating system and therefore anxiolysis and sedation (dose dependent)

25
Q

Benzodiazepines acting on central GABA vs spinal cord

A

Central GABA: enhances activity= anti-convulsant effect

Spinal cord: depress internuncial neurotransmission= muscle relaxation

26
Q

Benzodiaepines cardio effects

A

minimal

27
Q

Benzodiaepines resp effects

A

-minimal
-can enhance respiratory depression caused by other anesthetic agents- due to a reduced ventilatory response to CO2 and slight relaxation of intercostal muscles

28
Q

Benzodiaepines CNS effects

A

Overdose causes coma

29
Q

Diazepam

A

-adheres to plastic syringes (takes 12 hrs), sensitive to light degradation

-propylene glycol carrier (pH 6.8) making it painful on IM and has unreliable absorption

-has mordiazepam (active metabolites)

30
Q

Diazepam with pregnancy

A

Don’t use!

Diazepam will cross placenta, reach fetus

31
Q

Midazolam structure at different ph

A

**Contains imidazole ring
-At pH less than 4, ring opens and compound is water soluble
-pH greater than 4, ring closes and compound is highly lipophilic

32
Q

Midazolam administration

A

-can be administered IM, intranasal, transmucosal

-2-3x more potent than diazepam

-inactive metabolites

-popular in exotics

33
Q

Flumazenil

A

-Benzodiazepine antagonist- binds to GABA A receptor

-no side effects, increases muscle tone to normal and improves ventilation

-useful in exotics

-30-60mins duration IV, IM

34
Q

Trazodone

A

-behaviour modifier; decrease stress
-serotonin receptor antagonist and reuptake inhibitor (atypical antidepressant)

-oral admin may occur before visit

-can be combines with opioid

35
Q

Gabapentin

A

-mechanism underlying anxiolytic properties is unclear
-has inhibitory effect on voltage gated Ca channels in neural tissue decreasing the release of glutamate within CNS

-oral admin before visit possible

36
Q

What is gabapentin routinely used for?

A

-treatment of chronic pain
-epilepsy

Anesthesia (24 decks)

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