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Foundations- Anesthesia > Sedatives and Opioids > Flashcards

Sedatives and Opioids Flashcards

1
Q

describe the reasons for premedication (7)

A
  1. facilitate restraint
  2. anxiolysis
  3. muscle relaxation
  4. pre-emptive analgesia
  5. decrease required induction and maintenance anesthetics
  6. smooth induction
  7. modulate autonomic reflex activity
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2
Q

categorize the drugs used for premedication based on class and drug enforcement agency (DEA) scheduling

A

5 classes
1. phenothiazines
2. alpha-2 agonists
3. opioids
4. benzodiazepines
5. anticholinergics: now only if indicated by patient blood pressure and heart rate

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3
Q

describe the 5 DEA scheduling levels

A

Schedule 1:
-no currently accepted medical use; high potential for abuse (ILLEGAL); heroin, LSD< marijuana, ecstasy, peyote

Schedule II:
-high potential for abuse, but do have a medical reason for use
-pure mu agonists

Schedule III:
-moderate to low potential for dependence or abuse
-ketamin/buprenorphine

Schedule IV:
-low potential for abuse
-tramadol, benzodiazepines, butorphenol, alfaxolone

Schedule V:
-very low potential for abuse
-cough medicine with less then 200mg codeine

propofol and etomidate not controlled!

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4
Q

describe phenothiazines (acepromazine)

A
  1. sedative effect via antagonism of dopamine receptors
  2. label dose is 0.45mg/kg but this is hella high!
    -clinical dose is 0.01-0.05mg/kg
  3. does NOT provide analgesia
  4. onset of action takes up to 20 min and duration of action is 6-8 hours (long! but variable based on metabolic rate)
  5. there is no reversal and no way to increase clearance so if overdose = fucked until patient clears it itself
  6. can give IV, IM, SQ; can be mixed with other drugs
  7. NOT controlled by DEA
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5
Q

describe the effects of acepromazine on the body (pharmocadynamics)

A

CNS: dose dependent sedation

cardiovascular: vasodilation, unresponsive hypotension, anti-arrhythmic

respiratory: minimal

GI: anti-emetic

other:
-splenic sequestration of RBCs (can decrease PCV 20-30%)
-anti-histaminic
-paraphimosis in horses: makes it easy to clean sheath and more likely to die from anesthesia than to have its penis amputated!
-decreases platelet aggression: not super clinically relevant

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6
Q

give indications and contra1indications (6) of acepromazine

A

indications: suitable for exercise tolerant adult patients

contraindications/avoid in patients that are/have:
1. neonates
2. geriatric
3. heart disease
4. anemic
5. coagulopathic
6. hypotensive or cardiovascularly unstable

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7
Q

what 4 alpha agonists are available?

A
  1. dexmedetomidine: 1620:1
    -most frequently used in small animal, available in a gel for thunderstorm anxiety
    -much safer than xylazine for small animals
  2. romifidine: 340:1
    -associated with less ataxia in horses
  3. detomidine: 260:1
    -used frequently in horses, available in a gel
  4. zylazine: selectivity is 160 alpha 2 receptors for every alpha 1 receptors
    -oldest, still frequently used in horses, produces largest increase in blood glucose
    -ruminants are very sensitive! so only use 1/10 of the equine dose

difference in selectivity for alpha 2 over alpha 1 receptor = slightly different effects despite same MOA

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8
Q

describe alpha 2 agonists

A
  1. produce sedation and hypnosis
    -activate alpha-2 receptors in locus ceruleus of brain
    -decreases norepi centrally and peripherally resulting in sedation and analgesia
  2. rapid onset, short duration
  3. IV, IM, SQ; can be mixed with other drugs
  4. reversible
  5. not controlled by DEA
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9
Q

describe the cardiovascular effects of alpha 2 agonists

A

phase 1: vasoconstriction causes increased blood pressure causes reflex bradycardia and decreased CO but this is appropriate bc compensation

phase 2: resolution of vasoconstriction, persistent low HR (vagal effect) causes decreased blood pressure and decreased CO- up to 50% (doesn’t really effect them bc they’re sleeping)

arrhythmias:
1. sinus bradycardia
2. AV block (1st, 2nd, 3rd)
3. ventricular arrhythmias

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10
Q

describe respiratory, GI, genitourinary, and metabolic effects of alpha 2 agonists

A

respiratory: mild respiratory depression and milk pulmonary edema in small ruminants
-all small ruminants will have some measure of pulm edema but will occasionally be life threatening so be ready always! reverse and give furosemide or lasix

GI: decreased motility and occasional vomiting (xylazine to make cats vomit)

genitourinary:
-inhibit ADH = causes patients to urinate
-causes increased uterine wall tone

metabolic: inhibition of insulin release can lead to hyperglycemia

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11
Q

describe indications and contraindications (7) for alpha 2 agonists

A

indications: suitable for exercise tolerant adult patients

contraindications:
1. neonates
2. geriatrics
3. heart disease
4. anemic
5. cardiovascularly stable
6. diabetic
7. pregnant

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12
Q

describe reversal agents for alpha 2 agonists

A
  1. atipamizole: used to reverse dexmedetomidine (equal volume given even though actual reversal dose given is 10 times admin dose based on concentration)
  2. yohimbine: used in horses to reverse xylazine, romifidine, detomidine
  3. tolazoline: commonly used in food animals
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13
Q

what opioids are available?

A
  1. morphine
  2. hydromorphone
  3. oxymorphone
  4. methadone
  5. meperidine
  6. fentanyl
  7. buprenorphine
  8. butorphenol

common used for acute pain; animals can become biologically addicted so be careful

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14
Q

how are opioids classified?

A

based on receptor selectivity

pure mu: morphine, hydromorphone, oxymorphone, methadone, meperidine, fentanyl
-give most profound analgesia, moderate sedation

partial mu: buprenorphine; moderate analgesia (species dependent), moderate sedation

mixed agonist/antagonist: butorphernol, nalbuphine
-mild analgesia (think enough for a nail trim), moderate sedation

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15
Q

describe opioid receptors

A
  1. mu, kappa, delta
  2. present throughout body: brain, spinal cord, peripheral nociceptors, joint spaces, circulating immune cells
  3. endogenous ligand is endorphins
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16
Q

describe opioids

A
  1. mainstay of veterinary analgesia
  2. CONTROLLED by DEA
    -pure mu = Schedule II
    -partial mu = schedule III
    -mixed agonist/antagonist (butorphenol): schedule IV
  3. diversion is a big problem
  4. give IV, IM, SQ, transdermal, epidural; can mix with other drugs
  5. reversible
17
Q

describe the CNS, cardiovascular, respiratory, and GI effects of opioids

A

CNS: analgesia with species dependent sedation, euphoria, dysphoria, excitement

cardiovascular: may cause bradycardia (dose and drug dependent)

respiratory: dose dependent respiratory depression

GI: decreased motility, nausea, vomiting

all can cause histamine release! but worse with morphine, meperidine; may see hives, hypotension, hyperthermia, tachycardia

18
Q

describe specific adverse effects, duration of action, and water solubility of morphine

A

specific adverse effects: vomiting, histamine release

duration of action: 2-4 hours

water soluble so onset of action is 10-20 minutes, but in epidural space duration of action is up to 24 hours

19
Q

describe specific adverse effects and duration of action hydromorphone

A

vomiting, panting, hyperthermia in cats (only opioid that can increase temp!)

duration of action: 4-6 hours

20
Q

describe adverse effects and duration of actions of meperidine, of methadone, and of fentanyl and of buprenorphine and of butorphenol

A

meperidine: DOA 1 hour, may cause increase in heart rate

methadone: DOA 1-2 hours, can cause tremendous bradycardia requiring reversal, NMDA antagonist

fentanyl: DOA 30 min; administered as a CRI

buprenorphine: DOA 6-8 hours, mild adverse effects but DEA schedule III!

butorphenol: DOA 1-2 hours, mild adverse effects, causes more sedation than pure mu opioids via agonism of kappa receptors and can be used to reverse pure mu opioids

21
Q

what is neurolept analgesia?

A

opiod + major sedative; work synergistically to give more effective sedation and more profound analgesia

can use a lower dose of each drug for the same effect

22
Q

describe opioid antagonists

A
  1. naloxone:
    -most commonly used in vet practice
    -duration of action is 20-30 min so patients may re-narc when naloxone wears off
  2. naltrexone, nelmefene: longer DOA than naloxone, used commonly in wildlife/zoo immobilization
23
Q

what are 3 benzodiazepenes

A
  1. diazepam
  2. midazolam
  3. zolazepamh
24
Q

how do benzodiazepines work?

A
  1. causes sedation and anxiolysis via action at GABA receptors
  2. zolazepam only available as telazol with tiletimine
  3. midazolam is water soluble:
    -can be given IV, IM, SQ and can be mixed with other drugs
  4. diazepam is not water soluble, containing propylene glycol and ethanol
    -on admin it burns and has erratic absorption when given IM or SQ and should only be given IV
    -should NOT be mixed with any drug other than ketamine
  5. benzodiazepines are CONTROLLED by the DEA; schedule IV
  6. benzodiazepines do NOT provide analgesia
25
Q

describe CNS, cardiovascular, respiratory, GI, and musculoskeletal effects of benzodiazepines

A

CNS:
-depress limbic system, thalamus, and hypothalamus creating a calming effect
-anticonvulsant
-sedation is mild and usually not effective as a sedative in healthy adult patients

cardiovascular: minimal

respiratory: minimal

GI: diazepam is an appetite stimulant in cats

musculoskeletal: causes MSK relaxation

26
Q

describe clinical utility of benzodiazepines

A
  1. good choice for pre-med if
  2. neonates
  3. geriatric patients
  4. debilitated patients
  5. can cause excitement/dysphoria when used in healthy adult patients
  6. often used as a co-induction agent with NMDA agonists
27
Q

describe reversal of benzodiazepines

A

flumezenil: GAGA receptor antagonist, rarely necessary; usually only if bad trip

28
Q

how do you choose what drug to use to premed?

A
  1. species
  2. degree of analgesia necessary
  3. degree of sedation required
  4. personality of patient (bouncing lab versus calm greyhound)
  5. concurrent disease processes (avoid morphine in a patient with a mast cell tumor- histamine)
  6. presence or absence of IV catheter

Foundations- Anesthesia (6 decks)

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