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Anesthesia > Opioids 2 > Flashcards

Opioids 2 Flashcards

1
Q

clinical use of opioids

A

-premedication
-bolus or infusion intra and perioperatively (dose dependent analgesia, great anesthetic sparing effect)
-analgesia for medical and critically ill patients
-procedural sedation (combined with sedatives; sedation when administered alone in critical ill patients)

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2
Q

Adverse effects of opioids

A

-behavioural changes
-vomiting and nausea (morphine, hydromorphone)
-increased risk of gastroesophageal reflux (morphine, methadone)
-bradycardia
-respiratory depression

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3
Q

Opioids effect on CNS

A

-sedation
-euphoria
-dysphoria

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4
Q

Euphoria in dogs vs cats

A

Dogs: extreme wakefulness, vocalization

Cats: extreme friendliness, kneading, rolling

**may outlast analgesic effects

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5
Q

Dysphoria in dogs vs cats

A

Dogs: agitation, excitement, restlessness, excessive vocalization, disorientation

Cats: fearful, apparent hallucinatory behaviour, agitation, circling, pacing

**more likely in non-painful animals

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6
Q

Dysphoria

A

-Rxn to opioids
-animals difficult to distract or calm by interaction
-don’t respond to light palpation or painful area

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7
Q

How to treat dysphoria?

A
  1. partial opioid reversal with careful titration
    >Butorphanol (mu antagonists, kappa agonist)
    >Naloxon (mu antagonist)
  2. sedation (low dose acepromazine, dexmedetomidine)
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8
Q

Respiratory depression from opioids

A

-hypoventilation and hypercapnia
-dose dependent

-mu- opioid receptor decreases responsiveness of regulatory cells to pCO2 and pH

Eg. panting in dogs

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9
Q

Antitussive actions from opioids

A

-depression of cough reflex
-independent of respiratory depressant effects

*Butorphanol 100x/4x more effective than codeine/morphine

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10
Q

Cardiovascular effects from opioids

A

-minimal effects on cardiac output, cardiac rhythm, arterial blood pressure
-vagally mediated bradycardia
-histamine release= vasodilation and hypotension

-reversible with anticholinergic drugs

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11
Q

Nausea and emesis from opioids

A

**depends on opioid, dose, route of administration

Mu agonist opioids:
1. emetic effect- stimulation of dopamine receptors in chemoreceptor trigger zone (apomorphine)

2.Antiemetic effect- inhibition of emetic center inside BBB. Use of antidopaminergic drugs prior might decrease incidence of vomiting

Kappa opioids:
-Butorphanol: antiemetic for chemotherapy

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12
Q

Opioids effect on GI tract

A

-Decreased motility
-Gastro-esophageal reflux

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13
Q

Decreased motility from opioids

A

-inhibit the release of these NTs= impairing coordination of motility and inhibition of GI tract

**initially defecation followed by ileus and constipation

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14
Q

Gastro-esophageal reflux

A

Gastroesophageal sphincter relaxation

**caused by hydromorphone and methadone

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15
Q

Full mu agonists use

A

-superior analgesics; treatment of moderate to severe pain

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16
Q

Types of full mu agonists

A
  1. morphine
    2.hydromorphine
    3.methadone
    4.fentanyl
    5.meperidine
  2. sufentanil, alfentanil, remifentanil
17
Q

Morphine

A

-full mu opioid
-gold standard opioid to which others are compared
-administered IV, or neuraxially and intra-articularly

18
Q

Morphine affects

A

-histamine release if administered IV= hypotension
-vomiting

19
Q

Morphine-6-glucuronide

A

-active metabolite (650x more potent as morphine)
-pharmacological activities indistinguishable from morphine
-contributes significantly 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 potent than morphine
-used for moderate to severe pain; adequate for invasive surgery
-dose dependent sedation, respiratory depression, bradycardia

22
Q

Hydromorphone effects

A

-vomiting
-panting in dogs

-hydromorphone-3-glucuronide can produce neuro-excitatory behaviours

23
Q

Methadone

A

-pure mu agonist; NMDA antagonist
-Ne and serotonin uptake inhibitor
-no active metabolites
-similar to morphine

-Provides analgesia (moderate to severe, works on wind up pain; no vomiting; panting present)

24
Q

Fentanyl

A

-more powerful analgesic
-more potent than morphine (75-125x)
-used in intra and peri-operative pain
-anesthetic sparing (isoflurane requirements are reduced by 53% in dogs)
-highly lipophilic (high VD, long half life)

25
Q

Fentanyl timing

A

-fast onset
-short half life
>prolong context sensitive half lives (long recovery time, more problems in humans than dogs, cats)

**suitable for repeated boluses or infusions

26
Q

Fentanyl effects

A

More potent, so stronger effects
-dose dependent respiratory depressant
-dose dependent bradycardia

**too many repeated doses or to prolonged an infusion. May result in accumulation

27
Q

Meperidine

A

-synthetic mu and kappa agonist
-1/10 potency of morphine

28
Q

Meperidine timing

A

Short duration

29
Q

Meperidine effects

A

-mild analgesia
-histamine release
-decreased incidence of GER compared to morphine
-Cardiovascular effects:
>negative inotropy when administered alone to conscious dogs
>modest atropine-like effects= increase HR rather than typical bradycardia

30
Q

Remifentanil

A

-mu opioid agonist
-similar potency to fentanyl
-used for analgesia linked with intra-operative use. Need other analgesics before infusion is stopped
-metabolized by blood and tissue non-specific cholinesterases, so can be used with pregnant animals; independent of hepatic function

31
Q

Remifentanil timing

A

-ultra short acting: context sensitive half time (4min)

32
Q

Tramadol

A

-atypical mu receptor agonists
-inhibits reuptake of serotonin and NE
-mild analgesia; primarily due to O-desmethyltramadol (M1)

33
Q

M1

A

-acts as a full mu opioid agonist

34
Q

Tramadol in dogs

A

-do not produce substantial amounts of M1
-analgesic effects are predicted to be weak at best

35
Q

Tramadol in cats

A

-produce substantial amounts of M1 therefore likely an effective analgesic
-bitter taste of oral preparation makes dosing a challenge

36
Q

Buprenorphine

A

-partial mu agonist, weak kappa antagonist
-1000x higher affinity for mu receptor than morphine
-difficult to antagonize effects
-moderate intrinsic activity, moderate analgesia

37
Q

Timing of buprenorphine

A

Slower onset time than other opioids (15-30 mins)

Long duration : 6-8hrs

38
Q

Butorphanol

A

-kappa agonist, mu antagonist
-originally labeled as an antitussive agent in dogs
-min effect on cardiopulmonary function
-no histamine released
-short acting (30-90mins)
-mild analgesia

Anesthesia (24 decks)

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