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ANESTHESIA > 13 – Opioids II > Flashcards

13 – Opioids II Flashcards

1
Q

Opioids clinical use

A
  • Premedication
  • Bolus or infusion intra- and peri-operatively
    o Dose-dependent analgesia
    o Great anesthetic sparing effect
  • Analgesia for medical and critically ill patients
  • Procedural sedation
    o Combination with sedatives
    o Sedation
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2
Q

Adverse effects of opioids

A
  • Behavioural changes
  • Vomiting and nausea
  • Increased risk of gastroesophageal reflux (GER)
  • Bradycardia
  • Respiratory depression
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3
Q

CNS

A
  • Sedation
  • Euphoria (more common in cats)
  • Dysphoria (more common in dogs)
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4
Q

Euphoria dogs + cats

A
  • Dogs: extreme wakefulness, vocalization
  • *Cats: extreme friendliness, kneading, rolling
  • May OUTLAST analgesic effects
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5
Q

Dysphoria dogs + cats

A
  • *Dogs: agitation, excitement, excessive vocalization
  • Cats: fearful, apparent hallucinatory behaviour, circling, pacing
  • More likely in NON-painful in animals
  • *reaction to ‘overdose’ of opioids
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6
Q

Dysphoria treatment

A
  • Partial opioid reversal (careful titration)
  • Sedation (low dose acepromazine, dexmedetomidine)
    o Maybe do not for older animals
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7
Q

Partial opioid reversal to ‘treat’ dysphoria

A
  • Butorphanol
  • Naloxone
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8
Q

Dose-dependent respiratory depression (mu-opioid agonists)

A
  • Hypoventilation and hypercapnia
  • Mu-opioid receptor decreases responsiveness of regulatory cells to pCO2 and pH
  • Humans are more susceptible than animals
  • Panting in dogs (to decrease body T: hypothermia)
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9
Q

Antitussive actions

A
  • Depression of cough reflex
  • Independent of respiratory depressant effects
  • Butorphanol 100x/4x more effective than codeine/morphine
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10
Q

CV effects

A
  • Minimal effects on CO, cardiac rhythm, arterial BP
  • Vagally mediated bradycardia
  • Reversible with anticholinergic drugs
  • Histamine release: vasodilation and hypotension (morphine, meperidine)
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11
Q

Mu agonist opioids nausea and emesis effects

A
  • Emetic effect: stimulation of dopamine receptors in CTZ (apomorphine)
  • Antiemetic effect: inhibition of emetic center inside the BBB
    o Use of antidopaminergic drugs may decrease incidence of vomiting
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12
Q

Kappa agonist opioids nausea and emesis effects

A
  • Butorphanol: antiemetic for chemotherapy
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13
Q

GI tract effects

A
  • Decreased motility
  • Gastro-esophageal reflux (GER)
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14
Q

Decreased motility (GI)

A
  • Inhibit release of NT=impair coordination of motility and inhibition of GIT
  • Initial effect=defecation
  • Followed by ileus and constipation
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15
Q

Gastro-esophageal reflux (GER)

A
  • Gastro-esophageal sphincter relaxation
  • Hydromorphone, methadone
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16
Q

When would you use full mu-agonist opioids?

A
  • Moderate to severe pain
  • *superior analgesics
17
Q

Full mu-agonist examples

A
  • Morphine
  • Hydromorphone
  • Methadone
  • Fentanyl
  • Meperidine
  • Sufentanil, alfentanil, remifentanil
18
Q

Morphine

A
  • Full mu opiod
  • ‘gold standard’
  • ++ to +++
  • Histamine release if administered IV (hypotension)
  • Vomiting
  • Can be administered neuraxially and intra-articularly
19
Q

Morphine-6-glucruonide

A
  • Active metabolite (650x as potent as morphine)
  • Pharmacological activities indistinguishable from morphine
  • Contributes to clinical analgesia with chronic morphine administration
20
Q

Morphine-3-glucuronide

A
  • Little affinity for opioid receptors
  • May contribute to the EXCITATORY effects of morphine
21
Q

Hydromorphone

A
  • Full mu opioid agonist
  • 5-10x more potent than morphine
  • Analgesia ++ to +++
  • Dose-dependent sedation, respiration, bradycardia
  • Vomiting
  • Panting
  • Adequate analgesia for invasive surgery
22
Q

Hydromorphone-3-glucuronide can produce

A
  • Neuro-excitatory behaviours
23
Q

Metadone

A
  • Pure mu-agonist
  • NMDA antagonist (more for ‘wind up’ pain)
  • NE and serotonin uptake inhibitor
  • Analgesia moderate to severe pain
  • Clinically similar to morphine
  • *NO vomiting
  • No active metabolites
24
Q

Fentanyl

A
  • 75-125x more potent than morphine
  • Analgesia +++
  • Intra and peri-operative pain
  • Fast onset, short half-life (suitable for repeated boluses or infusions)
  • Dose dependent respiratory depressant and bradycardia
  • Anesthetic sparing
  • Highly lipophilic (very large Vd and long elimination half-life)
  • Too many repeated doses or too prolonged an infusion=may result in accumulation
  • Prolong context-sensitive half lives: long recovery time)
25
Q

Merperidine

A
  • Synthetic mu and kappa agonist
  • 1/10 potency of morphine
  • Short duration, mild analgesia
  • Histamine release
  • Decrease incidence of GER compared to morphine
  • Unique CV effects
  • NEGATIVE INOTROPHIC effects when administered along
  • Has modest ATROPINE-like effects=increase HR rather than typical bradycardia
26
Q

Remifentanil

A
  • mu opioid agonist
  • similar potency fentanyl
  • analgesia +++
  • ultra-shortening: context-sensitive half time
  • only suitable for intra-operative use
  • metabolized by blood and tissue non-specific cholinesterases
  • independent of hepatic function
  • *may use under general anesthetics
  • Ex. C-sections (effect on mom but not the puppies)
27
Q

Tramadol

A
  • Atypical mu-receptor agonist
  • Inhibits reuptake of serotonin and NE
  • Add humans
  • Not good for dogs
28
Q

Tramadol dogs

A
  • Do NOT produce substantial amounts of M1
  • Analgesic effects are predicted to be weak
29
Q

Tramadol cats

A
  • Produce substantial amounts M1: likely effective analgesic
  • Bitter taste of oral preparation=dosing is a challenge
30
Q

Buprenorphine

A
  • Partial mu-agonist (weak K-antagonist)
  • 1000x higher affinity for mu-receptor than morphine
  • Difficult to antagonize its effects
  • Moder intrinsic actiivy
  • Analgesia ++
  • Slower onset (15-30mins)
  • *ceiling effect (bell shape dose response curve, go higher=less effective)
  • Long duration: 6-8 hrs
31
Q

Butorphanol

A
  • Kappa agonist, mu antagonist
  • Minimal effects on cardiopulmonary function
  • No histamine release
  • Shorting acting (30-60mins)
  • Sedative properties
  • Analgesia +
32
Q

Butorphanol was labeled as an

A
  • Antitussive agent in dogs
33
Q

11-month old great pyrenees dog: hit by car, problem=coxofemoral luxation, going to do sedation for radiographs and closed reduction

A
  • Pain level: severe
  • Opioid: Hydromorphone (or Fentanyl)
  • Side effect example: panting
34
Q

3 year old DSH, ate walnuts, obstructive foreign bodies in stomach, plan: surgery

A
  • pain level: moderate
  • opioid: methadone (no vomiting), fentanyl (titre to effect)
35
Q

7 year old DSH, accidental drug overdose->cardiac arrest, successful chest compression

A
  • buprenorphine: every breath=hurt
  • butorphanol: no CV or respiratory side effects
36
Q

10 year old Yorkie, goose honking cough, suspect collapsing trachea, scheduled for radiographs under sedation

A
  • pain level: mild
  • opioid: butorphanol (no respiratory effect
    o can give IM
    o also mild sedative may decrease/calm breathing
37
Q

5 year old DSH, complicated humerus fracture, amputation (buprenorohine over night)

A
  • pain: severe
  • opioid: methadone, fentanyl, hydromorphone
  • *stop buprenorophine at midnight so doesn’t interfere with hydromorphine
38
Q

2 year old miniature horse, elective castration

A
  • Pain: mild
  • Opioid: don’t give a full mu-agonist, do a partial agonist
  • **butorphenol

ANESTHESIA (27 decks)

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