Induction Meds: Barbiturates (General)

Question 1

What drug class is represented by the figure below? How do you know this?

Answer 1

• Barbiturates
• Rapid redistribution & lengthy context-sensitive half-time (noted by fat build-up over time)

S19

Question 2

Where is the site of initial redistribution for barbiturates?

When is equilibrium between plasma concentrations & muscle concentrations reached?

Answer 2

• Skeletal muscles
• 15 min
  *mass decreased on elderly

S21

Question 3

Where is the main reservoir for barbiturates?
What does this mean clinically?

Answer 3

• Adipose tissue
• Dose on lean body weight and note cumulative effects of barbiturates.

S21

Question 4

What is the metabolism and excretion of barbiturates?

Answer 4

• Hepatic metabolism
• Renal excretion

S22

Question 5

What are Barbiturates bound and how much?

Answer 5

70 - 85% protein bound on Albumin

S22

Question 6

What are the characteristics of a non-ionized barbiturate?

Answer 6

• Lipophillic
• Acidotic environment is favored.

S23

Question 7

What are the characteristics of an ionized barbiturate?

Answer 7

• Lipophobic
• Alkalotic-favored

S23

Question 8

Why might barbiturates be considered cerebro-protective?

Answer 8

↓CBF & ↓CMRO₂

S23

Question 9

Regarding barbiturates, are S-isomers or R-isomers more potent?
Which is used clinically?

Answer 9

• S-isomer barbiturates are more potent
• Trick question. Racemic mixtures are only ones used.

S24

Question 10

What is the onset of Barbituates and how is the patient affected?

Answer 10

Rapid onset of 30 seconds

Rapid awakening due to rapid uptake

S19

Question 11

Elimination 1/2 of Barbituates is shorter for which population

Answer 11

Pediatrics

S22

Question 12

What were previous uses of Barbituates?

Answer 12

• Premedication
• treat Grand mal seizures
• rectal administration with uncooperative/young patients
• increased ICP
• cerebral protection
• induction

S23

Question 13

What would occur with accidental arterial administration of a barbiturate?
What is the treatment?

Answer 13

• Immediate, limb-threatening vasoconstriction.
• Lidocaine or papaverine injection as well as any other vasodilatory method.

S34

Question 14

What renal effects would one expect to see after barbiturate administration?

Answer 14

Transient ↓RBF and ↓GFR

S35

Question 15

How do you return to spontaneous ventilation with barbiturates?

Answer 15

Slow frequency or decrease tidal volume.

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Question 16

Scoliosis surgery with barbiturates will require ______ monitoring

Answer 16

Somatosensory Evoked Potentials** (SSEP)**

Commonly used to detect changes in nerve conduction and prevent impending nerve injury

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Question 17

2 to 7 days of barbiturate infusion will have ____________ metabolism of anticoagulation, phenytoin, TCAs, digoxin, corticosteroids, bile salts, and vit K. May persist for 30 days.

Answer 17

accelerate metabolism

(more frequent dosing will be required)

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