- Design
- Retrospective single-centre cohort, 2010–2020
- Population
- 185,455 adults having noncardiac surgery under ventilated general anaesthesia
- Primary outcome
- In-hospital mortality
- Effect
- aOR 1.63 (95% CI 1.36–1.86) per 5 mmHg decrease in mean ETCO₂ from the median
This retrospective cohort, published in Anesthesiology on 10 September, examined 185,455 adults having noncardiac surgery under general anaesthesia with mechanical ventilation at one French tertiary centre between 2010 and 2020. In-hospital mortality was 0.85%.
Lower mean intraoperative end-tidal CO₂ was associated with higher mortality in a non-linear way: each 5 mmHg fall below the median carried an adjusted odds ratio of 1.63. The association held after adjustment for minute ventilation and for the depth and duration of hypotension, and there was no interaction with hypotension.
End-tidal CO₂ reflects cardiac output and dead space as well as ventilation, so a persistently low value in a normally ventilated patient may be an early sign of low flow. This study cannot show that raising end-tidal CO₂ improves survival; it suggests the number is worth treating as a warning, not just a ventilator setting.
- Treat a persistently low end-tidal CO₂ with normal minute ventilation as a possible sign of low cardiac output.
- Check for hypovolaemia, embolism or falling output before adjusting the ventilator.
- Avoid unnecessary hyperventilation during routine anaesthesia.
- Record end-tidal CO₂ trends in the anaesthetic record for handover.
Why it matters
A number anaesthetists watch every minute may carry prognostic meaning beyond blood pressure.
Don't overread it
This was observational; it does not show that targeting a higher end-tidal CO₂ saves lives.
The statistics, in plain English
An adjusted odds ratio of 1.63 per 5 mmHg fall means each step down was associated with about 60% higher odds of dying in hospital, after allowing for ventilation and hypotension. Absolute mortality was low (0.85%), so the absolute increase is small.
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