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Anesthesia Pharmacology Review > Benzodiazepines > Flashcards

Benzodiazepines Flashcards

1
Q

What are the pharmacologic effects of Benzos?

A
  • Anxiolysis
  • Sedation
  • Anterograde amnesia
  • Anticonvulsant
  • Spinal-cord mediated skeletal muscle relaxation
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2
Q

What effect lasts longer with benzodiazepines, sedative or anterograde amnestic effect?

A

Anterograde amnesia

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3
Q

What benefits do Benzos have over Barbiturates?

A
  • Less tolerance
  • Less potential for abuse
  • Fewer SE’s
  • Don’t induce hepatic microsomal enzymes
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4
Q

What medication is the antagonist for benzodiazepines?

A

Romazicon (Flumazenil)

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5
Q

Which benzodiazepine is typically used in pre-op?

A

Midazolam (Versed)

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6
Q

Which benzodiazepines are preferred for post-op sedation?

A
  • Diazepam (Valium)
  • Lorazepam (Ativan)
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7
Q

What is the overall MOA of benzodiazepines?

A

GABA mediation:

  • Binding at BZD site
  • Enhances affinity of receptors for GABA
  • Open chloride channels and induces hyperpolarization.
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8
Q

What are the GABA-A/Y subunits we’re most concerned with?

A

α-1
α-2

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9
Q

What effects does the α-1 subunit cause when bound?

A
  • Sedation
  • Amnesia
  • Anticonvulsive
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10
Q

What effects does the α-2 subunit cause when bound?

A
  • Anxiolysis
  • Skeletal muscle relaxation
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11
Q

Which subunit is most abundant?

A

α-1

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12
Q

Where are α-2 subunits located?

A
  • Hippocampus
  • Amygdala
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13
Q

Where are α-1 subunits located?

A
  • Cerebral cortex
  • Cerebellar cortex
  • Thalamus
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14
Q

What other drugs can have an effect on GABA-A receptors?

A
  • Barbiturates
  • Etomidate
  • Propofol
  • Alcohol
  • Opioids
  • α-2 agonists (Precedex, Clonidine)
  • Inhaled anesthetics
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15
Q

What are the main differences between the benzodiazepines we use?

A
  • Onset and duration
  • Potency
  • Lipid solubility
  • Redistribution
  • Pharmacokinetics
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16
Q

What effect do BZD’s have on EEG waves?

A
  • Decreased alpha wave activity (relaxation)
  • Inability to produce isoelectric state (Versed)
  • Anterograde amnesia
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17
Q

What effect do BZD’s have on platelets?

A

Inhibition of platelet aggregating factors

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18
Q

What type of structure does a BZD have that provides stability and allows rapid metabolism?

A

Imidazole ring

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19
Q

Compared to Diazepam (Valium), how strong is Midazolam (Versed)?

A

2-3x more potent
ex. 1mg Versed vs. 10 mg Valium

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20
Q

What special considerations must be taken into account for patients coming off of midazolam-induced sedation?

A
  • Amnestic effects > sedation (hours)
  • Written post-op instructions
  • Ensure they’re accompanied by family/friend
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21
Q

At what pH is Midazolam water soluble?

A

pH < 3.5
(open ring, protonated)

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22
Q

At what pH is Midazolam lipid soluble?

A

pH > 4.0
(closed ring, unprotonated)

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23
Q

What makes Midazolam non-irritating to the veins?

A

Lack of propylene glycol

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24
Q

What is the onset for Midazolam IV?

A

1-2 minutes

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25
Q

What is the peak effect time for Midazolam?

A

5 minutes
(be sure to wait at least 5 mins to assess effects)

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26
Q

How extensively does Midazolam bind to plasma proteins?

A

96-98%

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27
Q

What is the elimination half-time for Midazolam?
What about in the geriatric population?

A
  • 2 hours
  • Doubled in elderly patients
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28
Q

What causes the short duration of action for midazolam?

A
  • Lipid solubility
  • Rapid redistribution
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29
Q

What is the volume of distribution for Midazolam?

A

1-1.5 L/kg
(Increased in the elderly, obese, and women)

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30
Q

What metabolizes Midazolam?

A

CYP3A4
(Hepatic and intestinal P-450 enzymes)

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31
Q

What does Midazolam metabolize into? How is it cleared?

A
  • 1-hydroxymidazolam
  • Active metabolite conjugated and cleared by kidneys
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32
Q

What drugs inhibit P-450 enzymes?

A
  • Cimetidine (Tagamet)
  • Erythromycin
  • CCBs
  • Antifungals
  • Fentanyl
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33
Q

Compared to Lorazepam what’s the clearance rate of Midazolam?

Compared to Diazepam, what’s the clearance rate of Midazolam?

A
  • 5x faster than Lorazepam
  • 10x faster than Diazepam
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34
Q

What occurs to CMRO2 and CBF with Midazolam?

A

Dose-related decrease

35
Q

What is the isoelectric effect of midazolam?

A

Unable to produce isoelectric EEG

36
Q

Midazolam is a potent __
(even in status epilepticus)

A

Anticonvulsant

37
Q

Midazolam preserves __ response to CO2.

A

Vasomotor

38
Q

Why is midazolam a great drug to give to neuro patients?

A

Does not increase ICP if there’s an issue with intracranial compliance

39
Q

What effects does midazolam have on the pulmonary system?

A
  • Decrease in ventilation (dose-dependent)
  • Decreased hypoxic drive
  • Transient apnea w/rapid administration
40
Q

In what population should you be careful with administration of Midazolam?

A

COPD patients
(increased ventilatory depression)

41
Q

What effects does Midazolam have on the oropharynx and pharynx?

A
  • Depressed swallowing reflex
  • Decreased upper airway activity
    (Increased aspiration risk)
42
Q

What effect does Midazolam have on patient HR and BP?

A
  • Increased HR
  • Decreased BP
    (Dose-dependent)
43
Q

What effect does Midazolam have on cardiac output?

A

No change
SVR is decreased
(Helpful in pts with CHF)

44
Q

Can Midazolam inhibit the BP/HR response seen with intubation?

A

No

45
Q

What is the sedation dosage of Midazolam for children?
When is the peak effect?

A

0.25-0.5 mg/kg (oral)
20-30 minutes

46
Q

What is the sedation dosage of Midazolam in adults?

What will be the peak effect time?

A

1-5 mg IV
5 minutes

47
Q

What is the induction dose of Midazolam?

A

0.1-0.2 mg/kg IV over 30-60 seconds

Facilitated by a preceding dose of opioid (1-3 minutes), 50-100 mcg of fentanyl (synergistic effect)

48
Q

What is the post-op sedation dosage of Midazolam?

A

1-7 mg/hr IV

49
Q

What is the max recommended time of use for Midazalom post-op?
Why?

A

2-3 days
Causes T-cell suppression, metabolite accumulation

50
Q

It is uncommon to use midazolam for ___________. Instead, supplemented with opioids, propofol, and volatiles.

Midazolam is rarely associated with _____________ or ______________.

A

Maintenance (but decreases the requirement for volatiles)

N/V; emergence excitement (crazy)

51
Q

Which benzodiazepine is highly lipid soluble and has a more prolonged duration of action compared to Midazolam?

A

Diazepam (Valium)
(Rarely used in anesthesia)

52
Q

What substance is in Diazepam that causes irritation and burning to the veins?

A

Propylene glycol

53
Q

What is the onset time for Diazepam?

A

1-5 minutes

54
Q

What is the elimination half-time for Diazepam?

A

20-40 hours

55
Q

What metabolizes Diazepam?

A

CYP3A4

56
Q

What are the active metabolites of Diazepam?

A
  • Desmethyldiazepam
  • Oxazepam
57
Q

What is a major concern with Diazepam metabolism?

A

Return of drowsiness 6-8 hours post

58
Q

What occurs to CMRO2 and CBF with Diazepam administration?

A

Decrease
(Similar to Midazolam)

59
Q

What is the isoelectric effect of Diazepam (Valium)?

A

Can produce isoelectric EEG

60
Q

What is the anticonvulsant dosage of Diazepam?

A

0.1 mg/kg IV

61
Q

What conditions can be treated with Diazepam?

A
  • DT’s
  • Status epilepticus
  • Lidocaine toxicity r/t seizures
62
Q

What medication is typically given with Diazepam when used as an anticonvulsant?

A

Fosphenytoin (Cerebyx)

63
Q

What are the pulmonary effects of diazepam?

A

A slight decrease in tidal volume that can be exaggerated with opioids, alcohol, and COPD

64
Q

After __ mg/kg IV of Diazepam, there will be an increase in PaCO2.

A

0.2 mg/kg

65
Q

What reverses ventilatory depression caused by Diazepam?

A

Surgical stimulation
(Ideal for COPD patients)

66
Q

What are the cardiovascular effects of diazepam?

A

BP: Minimal
CO: Minimal
SVR: Minimal
BP changes with opioids and unchanged with the addition of nitrous

67
Q

What are the neuromuscular effects of diazepam?

A
  • Decrease skeletal muscle tone
  • Decrease tonic effect on spinal neuron
    Tolerance to skeletal muscle relaxant effects develops over time
68
Q

What is the induction dose for Diazepam?
What are the considerations when it comes to dosing for the elderly, patients with liver disease, or the presences of opioids?

A

0.5-1.0 mg/kg IV
Decrease dose by 25% to 50%

69
Q

Which BZD has the most potent sedative and amnestic effects?

A

Lorazepam (Ativan)

70
Q

Lorazepam is ___ soluble.

This drug has a ___ onset of action and __ metabolic clearance when compared to midazolam.

A

Lipid soluble (insoluble in water, will have irritation)

Slower onset and slower metabolic clearance.
(slower entrance to CNS too)

71
Q

What is the IV dose of Lorazepam?

A

1-4 mg

72
Q

What is the onset time for Lorazepam?
What is the peak effect time?

A

1-2 minutes (IV)
20-30 minutes (IV)

73
Q

What is the elimination half-time for Lorazepam?

A

14 hours

74
Q

What is different about the metabolism of Ativan compared to Versed and Valium?

A

Not entirely dependent on the CYP450 enzyme.
Works via glucuronidation

75
Q

Why is Lorazepam a good option for liver patients?

A

Conjugated into inactive metabolites

76
Q

Which drug acts as a competitive antagonist with a high affinity for BZD receptors and reverses all agonist activity of BZDs?

A

Flumazenil (Romazicon)

77
Q

How is Flumazenil metabolized?

What does it metabolize into?

A

CPY P450, CYP3A4

Inactive metabolites.

78
Q

What is the inital dosing of Flumazenil?

A

0.2 mg IV titrated to consciousness
Repeat 0.1 mg q1 minute to 1 mg total

79
Q

What is the dosing of Flumazenil to reverse sedation?

A

0.3 to 0.6 mg

80
Q

What is the dosing of Flumazenil for Benzodiazepine overdose?

A

0.5 to 1.0 mg

81
Q

What to do if the patient is still unconscious after using 1.0 mg of flumazenil?

A

Given Narcan
Consider other intoxicants

82
Q

What is the duration of flumazenil?

What is the continuous infusion rate of flumazenil?

A

30-60 minutes (half-time for BZD are longer, may need to redose)

0.1 to 0.4 mg/hr

83
Q

What are the side effects of high dose flumazenil?

A
  • Acute anxiety
  • Hypertension/tachycardia
  • Neuroendocrine evidence
  • Change in MAC of volatiles
84
Q

What are the special considerations to take when using flumazenil?

A

Contraindicated if BZDs are used as an antiepileptic drug, can precipitate acute withdrawal seizures.

Anesthesia Pharmacology Review (2 decks)

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