Induction Drugs (Etomidate) (Exam II)

Question 1

In general, thiobarbiturates are much more _____ soluble and have a greater _______ than oxybarbiturates.

What atom do thiobarbiturates have in lieu of an oxygen in the second position (like oxybarbiturates)?

Answer 1

• Lipid; potency
• Sulfur

Question 2

What is unique about Etomidate’s organic chemical structure?

Answer 2

It is the only carboxylated imidazole containing compound.

Question 3

When is etomidate water-soluble vs lipid-soluble?

Answer 3

• H₂O-soluble at acidic pH.
• Lipid-soluble at physiologic pH.

Question 4

What percentage of etomidate is propylene glycol? What is the result of this?

Answer 4

• 35% propylene glycol resulting in pain on injection.

Question 5

Which induction agent can be given without an IV? How is this?

Answer 5

Etomidate - can be given sub-lingual.

Question 6

Why does etomidate have a low incidence of myoclonus?

Answer 6

• Trick Question. Etomidate has a high incidence of myoclonus, just like all other induction agents.

Question 7

What is the onset of etomidate?
How much of it is protein bound?
What protein does it bind to?

Answer 7

• Onset: 1 minute
• 76% albumin bound

Question 8

What is etomidate’s Vd?
How does clearance compare to thiopental?
What is the result of this clearance?

Answer 8

• Large Vd
• 5x faster clearance than thiopental resulting in a prompt awakening.

Question 9

What metabolizes etomidate?
What is the elimination profile? (E1/2, excretion)

Answer 9

• CYP450’s & plasma esterases
• Elimination ½ time = 2-5 hours with 85% via urine and 10 - 13% via bile.

Question 10

What is the induction dose for etomidate?

Answer 10

• 0.3 mg/kg IV

Question 11

What is the best use for etomidate?

Answer 11

• Induction for unstable cardiac patients. (Minimal changes to HR, SV, CO, contractility)
  -Good choice for low EF
  -alternative to propofol or barbiturates for induction

Question 12

What needs to be used concurrently with etomidate when performing a laryngoscopy? Why?

Answer 12

• Opioids, etomidate has no analgesic effects.

Question 13

What is Etomidate’s most common side effect?
How often does this occur?

Answer 13

• Involuntary Myoclonic Movements ( 50 - 80 %) of administration.

Question 14

What can be administered with etomidate to prevent involuntary myoclonic movements?

Answer 14

Fentanyl 1-2 μg/kg IV

Question 15

Etomidate has a dose dependent inhibition of the conversion of cholesterol to _________.
What does this mean clinically?

Answer 15

• Cortisol
• Etomidate decreases SNS capability to respond to stress (longer vent times, severe hypotension, etc.)

Question 16

How long does adrenocortical suppression with etomidate last?
What two pathologies would cause you to hesitate before giving etomidate?

Answer 16

• 4 - 8 hours.
• Sepsis & hemorrhage (anything where you need an intact cortisol response).

Question 17

Compared to thiopental, etomidate will lower plasma concentrations of what substance?

Answer 17

Cortisol

Question 18

What are etomidate’s effects on CBF & CMRO₂ ? Why?
What effect does etomidate have on ICP?

Answer 18

• Etomidate = ↓CBF & ↓CMRO₂ due to being a direct cerebral vasoconstrictor.
• Will also ↓ICP.

Question 19

CMRO₂ is couple with both CBF and _______.

Answer 19

CMRG (cerebral metabolic requirement of glucose)

Question 20

What is the EEG profile of etomidate?

Answer 20

• More excitatory than thiopental
• May activate seizure foci
• Augments SSEP amplitude.

Question 21

Though etomidate is great for cardiac patients, what condition can result in significant hypotension if not treated prior to induction?

Answer 21

• Hypovolemia
  (etomidate causes a decrease in SVR)

Question 22

Histamine release via etomidate is mediated through what?

Answer 22

• Trick question. Etomidate does not release histamine.

Question 23

What is the pulmonary profile of etomidate?

Answer 23

• Less respiratory depression than barbiturates
• Rapid IV produces apnea
• Stimulates CO₂ medullary centers

Question 24

What is the mechanism of action of etomidate?

Answer 24

selective modulator of GABA-A receptors