Intravenous induction agents: Propofol

Question 1

Propofol: formulation

Answer 1

1% or 2% propofol
2.25% glycerol
1.2% purified egg phosphatide
Soya bean oil
Sodium hydroxide

Question 2

Propofol: molecular weight

Answer 2

178.28

Question 3

Propofol: pH

Answer 3

7-8.5 (in emulsion)

Question 4

Propofol: stability

Answer 4

Stable at room temperature

Not light sensitive

Question 5

Propofol: elimination half life

Answer 5

4-7 hours

Question 6

Propofol: clearance

Answer 6

20-30 ml/kg/min

Question 7

Propofol: volume of distribution

Answer 7

2-10 L/kg

Question 8

Propofol: mechanism of action

Answer 8

Binds to beta subunit of GABA receptor causing hyperpolarization

Question 9

Propofol: pKa

Answer 9

11 (weak acid so almost entirely un-ionized at pH 7.5)

Question 10

Propofol: protein binding

Answer 10

98% (almost entirely bound to albumin)

Question 11

Propofol: metabolism

Answer 11

Conjugated to inactive metabolites by the liver (CYP 2B6 and CYP 2C9) and excreted in the urine (can give green tinge)
Some extrahepatic metabolism occurs in the lungs

Question 12

Propofol: bolus dose

Answer 12

2mg/kg (may be as little as 1mg/kg in the elderly; children may need more)

Question 13

Propofol: infusion dose

Answer 13

0.3-4 mg/kg/h infusion rate

Question 14

Propofol: on injection

Answer 14

Can cause pain/coolness (can be ameliorated with lidocaine)

Question 15

Propofol: CNS effects

Answer 15

Causes rapid and smooth GA in one arm brain time
May cause excitatory movements - not true seizures
Dose dependant cortical depression

Question 16

Propofol: cardiovascular effects

Answer 16

Dose dependent reduction in systemic vascular resistance and bradycardia (especially with concurrent opioid)

Question 17

Propofol: respiratory effects

Answer 17

Respiratory depression and apnoea

Reduced laryngeal reflexes (good for LMA)

Question 18

Propofol: porphyria

Answer 18

Safe to use

Question 19

Propofol infusion syndrome

Answer 19

Fat overload syndrome after prolonged infusion (>4ml/kg/h for >48h)
Classically consists of hyperlipidaemia, fatty infiltration of the heart (causing Brugada-like ECG in V1-3), rhabdomyolysis, renal failure