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Flashcards in Methohexital Deck (23)
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1
Q

What is the trade name of Methohexital?

A

Brevital

2
Q

What is the formal drug class of Methohexital?

A

Barbiturate/ Oxybarbiturate

3
Q

What are the clinical uses of Methohexital?

A
  • IV/IM/Rectal induction and IV maintenance of anesthesia in short procedures with minimal painful stimuli
  • treatment of Increased ICP
4
Q

What is the MOA of Methohexital?

A
  • produces sedative-hypnotic effects via interaction with GABA in the CNS and by depressing the RAS
  • GABAa increases transmembrane chloride, resulting in hyperpolarization of the post-synaptic cell membrane and thus inhibition of the post-synaptic neurons
  • also targets glutamate, adenosine and neuronal nicotinic receptors
  • selectively depresses transmission in SNS ganglia resulting in decreased BP during IV administration
5
Q

How is Methohexital metabolized?

A
  • Occurs in the liver through N-dealkylation and oxidation to inactive metabolites
  • side chain oxidation to form the inactive metabolite, 4-hydromethohexital is the most important biotransformation involved in termination of biologic activity
6
Q

What is the elimination 1/2 life?

A

4 hours

7
Q

How is Methohexital cleared?

A

-much higher hepatic extraction ratio (compared with TPL) therefore hepatic blood flow and cardiac output more likely to influence metabolism

8
Q

What is the redistribution of Methohexital?

A
  • IV administration results in rapid uptake by the brain (within 30 secs) and rapid induction of sleep
  • early awakening is a result of redistribution away from CNS
9
Q

What is the DOA of Methohexital?

A

5-10 minutes as a result of its lipid solubility and rapid redistribution into muscle and organs with high blood flow

10
Q

How is Methohexital eliminated?

A

clearance 9.3-12.1 mL/kg/min

Excreted via the kidneys

11
Q

What is the volume of distribution of Methohexital?

A

Vd is 1.9-2.2 L/kg

12
Q

Is Methohexital protein bound?

A

approximately 73%

13
Q

What are the CNS side effects of Methohexital?

A
  • Hiccups, coughing, and/or muscle twitching
  • produces a dose-dependent decrease in CMRO2 by up to 50% of normal
  • Reduction in O2 requirements may offer protection during transient focal ischemic events
  • seizures may be elicited in those with previous history of convulsive activity, especially partial seizure disorder
  • cerebral vasoconstriction with reduction in cerebral blood flow and ICP- cerebral perfusion pressure maintained because reduction in ICP exceeds MAP
  • pain on injection
14
Q

What are the respiratory side effects of Methohexital?

A
  • Depressed ventilatory response to hypercarbia or hypoxemia as a result of central depression
  • dose dependent decrease in RR and TV- apnea may result for 30-90 seconds after a sleep dose
15
Q

What are the CV effects of Methohexital?

A

-following induction, temporary dose-dependent decrease in ABP and CO, and reflex tachycardia

16
Q

What are the contraindications to the use of Methohexital?

A
  • Contraindicated in patients who cannot tolerate GA
  • Porphyria
  • known sensitivity
17
Q

When should Methohexital be used with caution?

A
in patients with:
asthma
obstructive pulm. disease
severe HTN or hypotension
Hypovolemia
Myocardial disease
CHF
Severe anemia
Extreme obesity
18
Q

Metabolism of Methohexital is influenced by what other drugs?

A
Phenytoin
Halothane
Anticoagulants
Corticosteroids
Ethyl Alcohol
Opioids
Propylene Glycol
19
Q

What should NOT be mixed with Methohexital?

A

Succinylcholine and other

Acidotic medications because precipitation will occur

20
Q

What is the induction dose of Methohexital?

A

1 - 2 mg/kg IV of 1% solution

21
Q

What is the maintenance IV dosage of Methohexital?

A

Intermittent injections of 20-40mg of 0.2% or 1% solution every 4-7 minutes, or as required

22
Q

What is the rectal dose of Methohexital and when is it usually used?

A

20 - 30 mg/kg for induction of anesthesia in uncooperative or pediatric patients

23
Q

What is an important airway consideration of Methohexital?

A

-it does not completely obtund a/w reflexes; asthmatics may develop bronchospasm and lightly anesthetized patient may develop laryngospasm