Barbiturates

Question 1

Barbiturates Mechanism of Action

Answer 1

Interaction with GABA A (alpha subunit) receptor, directly activate chloride ion channels, increasing their duration of opening (increases efficacy of GABA), hyperpolarization of postsynaptic cell membranes, also blocks AMPA receptor (glutamate)

Question 2

Barbiturates Protein Binding

Answer 2

83%

Question 3

Barbiturates Lipid Solubility

Answer 3

High - rapid into CNS, uptake in 30 seconds & prompt awakening after single dose

Question 4

Barbiturates Metabolism

Answer 4

Hepatic

Question 5

Barbiturates Excretion

Answer 5

Renal

Question 6

Barbiturates CV Effects

Answer 6

Decrease: SBP, CO & SVR - cardiac depression & increased venous capacitance, Increase: HR (rebound)

Question 7

Barbiturates Pulmonary Effects

Answer 7

Respiratory depression, apnea, return with slow RR & tidal volume

Question 8

Barbiturates CNS Effects

Answer 8

Decrease: CBF, ICP, CMRO2

Question 9

Barbiturates Renal

Answer 9

Modest decrease in blood flow & GFR

Question 10

Barbiturates pH effects

Answer 10

Metabolic acidosis increase effects, metabolic alkalosis decreases effects of barbs, & respiratory acidosis has much less effect

Question 11

Thiopental supplied as

Answer 11

25 mg/mL

Question 12

Methohexital supplied as

Answer 12

10 mg/mL

Question 13

Induction dose of thiopental

Answer 13

3-5 mg/kg

Question 14

Induction dose of methohexital

Answer 14

1-1.5 mg/kg (20-30mg/kg rectal)

Question 15

Barbiturates Be aware of

Answer 15

May cause hyperalgesia, can cause histamine release, Extravasation causes tissue sloughing, do not mix with succ (will make “concrete”), intraarterial injection causes severe vasoconstriction, induces the P450 system, contraindicated in patients with acute intermittent porphyria