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Anesthesia > Opioids > Flashcards

Opioids Flashcards

1
Q

Which opioid is Fentanyl chemically related to?

A

Meperidine

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2
Q

Describe chemical component of opioids:

  • acid/base
  • protein binding
  • neutral o rionized
A

weak base
high protein binding
largely ionized at physiologic pH

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3
Q

How would causing decreased protein binding and un=ionized forms of opioids effect their behavior?

A
  • shorter latency to peak effect
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4
Q

MOA of opioids (general/basic)

A

Bind opioid receptor- G protein linked
downstream effects cause hyperpolarization of cell, and decreased neuronal excitability

mediators- K+ channel, AC, MAPK, Voltage gated Ca+ channels

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5
Q

Name the types of opioid receptors

A

mu
kappa
delta
(ORL1)- unclear clinical relevance

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6
Q

Major effect of opioids at

  1. spinal cord
  2. brainstem
  3. forebrain
A
  1. Spinal cord
    a. inhibit release of substance P from primary sensory neurons in DH (mitigates painful sensation transfer to brain)
  2. Brainstem- block nociceptive transmission from DH of SC via descending inhibitory signals
  3. Forebrain- alter affective response to pain
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7
Q

General metabolism of opioids

A

Hepatic microsomal metabolism (conjugation)

Excreted by kidney

not case with all

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8
Q

Order the following opioids from QUICKEST peak effect to SLOWEST peak effect for a BOLUS

morphine
fentanyl
sufentanil
alfentanil
remifentanyl
A

Alfentanil/Remifentanil –> Fentanyl –>Sufentanil –>Morphine

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9
Q

Order the following opioids from QUICKEST peak effect to SLOWEST peak effect for a INFUSION

morphine
fentanyl
sufentanil
alfentanil
remifentanyl
A

Remifentanil –>Alfentanil –> Sufentanil –>Fentanyl/Morphine

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10
Q

Which opioids would be preferred in bolus form if you desire a brief duration with rapid dissipation?

A

Remifentanil or Alfentanil

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11
Q

Which opioid is best suited for a PCA? Why?

A

Fentanyl > Morphine

Peak effect as seen on front end kinetics shows that greatest effect of Fenatnyl occurs before “lock out period” ends for PCA…avoiding dose stacking and OD risk

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12
Q

What determines the latency to peak effect?

which factors effect this most?

A

speed that plasma and effect site come to equilibrium

i.e. Faster = Higher proportion of drug that is “diffusible”, i.e. unbound and un-ionized.

Faster = higher lipid solubility

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13
Q

Clinical implication of stead-state concentration of opioid constant rate infusion? Exception to this?

A
  • Latency to reach steady state effect
  • demonstrates need for bolus prior to infusion to bridge to peak effect

Exception: Remifentanil

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14
Q

Which drug is a good choice for total IV anesthesia for opioids?

A

Remifentanil- reaches a steady state quickly (drug will not be continuing to increase in concentration for hours despite continued or lowered infusion rate)

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15
Q

Define Context Sensitive Half Time (CSHT)

A

Time required to achieve a 50% decrease in concentration of drug after stopping continuious steady state infusion

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16
Q

How does decrease in opioid rate change over time re: infusion duration?

A

Longer duration = longer CSHT (Except Remifentanil)

Helps to determine which opioid is best based on case duration and length of time needed for drug

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17
Q

Major Mu opioids

A

morphine, fentanil

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18
Q

Major opioid group with venitilatory depression

A

mu

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19
Q

major opioid group with GI effects

A

mu and kappa

20
Q

major opioid groups causing sedation

A

mu and kappa

21
Q

Major side effects of opioids

A
  1. Supraspinal/spinal analgesia
  2. Miosis (small pupils)
  3. cough suppression
  4. vasodilation (hypotension)
  5. Bradycardia
  6. ventilatory depression
  7. increased biliary pressure
  8. n/v
  9. constipation/illeus
  10. delayed gastric emptying
    11urinary retention
  11. muscle rigidity
  12. pruritis
22
Q

Which “type” of pain are mu opioids best at treating?

A

“second pain” - slow conducting unmyelinated C fiber pain

vs “first pain” via small myelinated A delta fibers or neuropathic pain

23
Q

MOA of opioid induced vent depression

A

alter vent response to arterial CO2 in medulla (threshold for increase is paCO2 of 40 mmHg, linear increase there after, but slowed)

Both Vt and RR decrease –> progress linearly with increased conc until apnea

regulated via mu receptor

24
Q

Factors increasing risk for opioid OD

A
  1. large opioid dose
  2. old age
  3. use of other CNS depressants (benzos, etc)
  4. renal insufficiency (for morphine)
  5. natural sleep
25
Q

CV effects of opioids (fentanyl, morphine)

Fentayl vs Morphine, greater CV effects?

A

Bradycardia (increased vagal nerve tone)

hypotension (vasodilation via brain effects, decrease pre and afterload)

Morphine > Fentanyl

26
Q

Side effect that may make ventilation difficult with bolus doses of fentanyl?

A

muscle rigidity, causing vocal cord rigid/closure (hard to ventilate)

can be eliminated by NM blocking drugs

27
Q

MOA of opioid induced nausea

A

chemoreceptors in area postrema on floor of 4th ventricle

worse with movement

28
Q

Major pharmacokinetic interaction of opioids with other drugs

A

Propofol

Opioids given with propofol infusion result in higher opioid concentrations

29
Q

Major pharmacodynamic effect of opioids with other medications

A

synergy when combined with sedatives

moderate opioid levels dramatically reduce MAC of inhaled anesthetics (substantially, up to 75%).

Reduction is NOT complete…opioids are not a complete anesthetic

30
Q

Which opioid is completely unaffected by the anhepatic phase of a liver transplant?

A

remifentanil- metabolism is completely unrelated to hepatic clearance

31
Q

Pt population at increased risk of sedative effects of opioids?

A

pts with hepatic encephalopathy

32
Q

Which opioids are affected by renal failure?

A

morphine - nearly half of the conjugation of morphine occurs in the kidney (in addition to excretion of m3g and m6g*active)

meperidine - active metabolites are excreted by kidneys. build up of normeperidine causes tremors, anxiety, frank seizures

33
Q

Gender differences in opioid effects

A

Morphine - more potent in women, slower onset in women

34
Q

Age differences in opioid effects

A

older = more potency of fentanyl cogeners

Decreased clearance and decreased distribution volume

RESULT: decreased dose requirements (50% reductions) for pts > 65yo

35
Q

Obesity effects on opioids

A

Opioid requirements based on lean total body mass, not TBW

extremely obese people will not require doses suggested by their weight because lean body mass is smaller

36
Q

What is the active component of codeine?

A

morphine is active compound of this prodrug

37
Q

Side effects of morphine limiting its use intraoperatively? why?

A

Histamine release = hypotension (and itching)

38
Q

Fentanyl routes of administration

A 
IV
transdermal
transmucosal
transnasal
transpulmonary
39
Q

Describe metabolism of alfentanil

A

liver via cyp3a4 (somewhat unrpredictable due to interindividual variation in this enzyme)

40
Q

most potent opioid used in anesthesia practice

A

sufentanil

41
Q

metabolism of remifentanyl

A

ester hydrolysis

loses mu reactivity = short half life

42
Q

speed and duration of action of remifentanyl

A

quick on and quick off (due to hydrolysis)

short CSHT (5 min)

  • latency similar to alfentanil
  • potency slightly less than fentanyl
43
Q

Commonly used meds in total IV anesthesia

A

Remifentanil + Propofol

44
Q

Questions to ask when choosing and opioid

A
  1. how quick does it need to work?
  2. how long will i need it to work?
  3. How important is it that vent depression/sedation go away quickly?
  4. will the opioid need to be titrated intraop (big changes in analgesia requirements)?
  5. will there be a lot of pain post-op?
45
Q

Your patient is getting a retrobulbar block and you need a brief pulse of opioid effect and then rapid recovery:

What med?

A

Bolus Remifentanil/Alfentanil

46
Q

Your patient is getting a craniotomy, and neurosurgery wants to do a neuro exam on table immediately post-op (need good pain control, but awake/alert soon after procedure:

what med?

A

remifentanil infusion

47
Q

Need long-lasting pain control, and post-op pain likely to be high?

A

fentanyl infusion

Anesthesia (9 decks)

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