- Design
- Retrospective single-centre cohort
- Population
- 341,199 adults having propofol sedation or volatile general anaesthesia
- Primary outcome
- Propofol infusion dose and age-adjusted end-tidal MAC
- Effect
- Non-medical use +6.85 µg/kg/min propofol (95% CI 6.07 to 7.63); +0.01 MAC
A single-centre retrospective cohort in the British Journal of Anaesthesia (published 29 September) analysed 341,199 adults who had propofol sedation or volatile-based general anaesthesia in Boston between 2008 and 2024. About 7% were non-medical cannabis users and 0.9% held medical cannabis certification.
After adjustment, non-medical users received about 6.85 micrograms per kg per minute more propofol during sedation (95% CI 6.07 to 7.63), and daily users about 8.4 more. Medical users received about 2.9 more. Volatile requirements were higher by only 0.01 to 0.02 MAC. Non-medical users also had a slightly larger heart rate rise after intubation (about 1.5 beats per minute).
Earlier, smaller studies suggested cannabis users need substantially more anaesthetic, and some anaesthetists pre-emptively increase doses. These data show a real but modest effect. Asking about cannabis use, particularly daily use, still matters for titration and airway reactivity, but it is not a reason to change induction doses by large amounts.
- Ask every patient about cannabis use, including frequency and route, at pre-assessment.
- Expect a modestly higher propofol requirement in daily cannabis users and titrate to effect.
- Avoid large pre-emptive dose increases based on cannabis use alone.
- Record cannabis use in the anaesthetic chart so future anaesthetists can anticipate requirements.
Why it matters
It corrects an inflated expectation that could lead to over-dosing cannabis users at induction.
Don't overread it
This was observational and relied on recorded cannabis use, which is likely under-reported.
The statistics, in plain English
In a cohort this large, very small differences become statistically significant. An extra 0.01 MAC is clinically negligible; an extra 7 micrograms per kg per minute of propofol is a modest increase, roughly a few percent of a typical sedation infusion.
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