Context-sensitive half-life is used to predict recovery from continuous IV infusion. After a 4-hour propofol infusion at anaesthetic doses, what is the approximate context-sensitive half-life?
- A Approximately 10 minutes
- B Approximately 2 hours
- C Approximately 40 minutes ✓
- D Approximately 6 hours
Correct answer: C. Approximately 40 minutes
Explanation
Context-sensitive half-life (CSHL) is the time for plasma concentration to fall by 50% after stopping an infusion, where 'context' refers to duration of infusion. Propofol's CSHL after a 4-hour infusion is approximately 30–40 minutes, making it favourable for TIVA techniques. After 8 hours, it rises to about 60–70 minutes but remains shorter than thiopental (which has a very context-sensitive CSHL). This contrasts with remifentanil whose CSHL remains ~3 minutes regardless of infusion duration due to organ-independent ester hydrolysis.
Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.
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Written and medically reviewed by the StethoPrep medical team.