Design: Pooled analysis of three clinical studies with emissions modelling
Population: 132 ASA I to III patients receiving sevoflurane at 0.2 to 4 l/min fresh gas flow
Primary outcome: First-hour CO2 equivalent emissions by component
Effect: Sevoflurane 2.4 to 18.6 kg CO2e across flows; carrier gas plus absorbent under 3% of total

An analysis in Anesthesiology (29 September 2026) combined data from three studies of 132 patients given sevoflurane at constant end-tidal concentration, by manual, target-controlled or automated closed-circuit delivery, across fresh gas flows from 0.2 to 4 l/min. It calculated the carbon dioxide equivalent emitted in the first hour by the sevoflurane, the oxygen and air, and the carbon dioxide absorbent.

Sevoflurane emissions rose in a straight line with fresh gas flow, from 2.4 kg to 18.6 kg CO2 equivalent, apart from a short high-flow wash-in at low flows. Carrier gas and absorbent together contributed less than 3%, even in closed-circuit delivery, so the concern that low flow simply swaps vapour for soda lime does not hold.

This is a modelling analysis of one hour, not a full life-cycle assessment. But its practical message is direct. The largest climate gain in an inhalational anaesthetic comes from turning the flow down and not running a higher end-tidal concentration than the patient needs.

After a brief wash-in, consider reducing fresh gas flow to 1 l/min or lower during maintenance where your machine and monitoring allow.
Do not avoid low flow out of concern for absorbent use; its footprint was negligible here.
Titrate end-tidal sevoflurane to the lowest concentration that meets the patient's needs.
Use target-controlled or automated delivery where available to make low flow easier.
Audit fresh gas flows in your department; habit often keeps them high.

Why it matters

It removes the main objection to low-flow anaesthesia and puts a number on what each litre per minute costs.

The statistics, in plain English

Moving from 4 to 0.2 l/min cut first-hour sevoflurane emissions from about 18.6 to 2.4 kg CO2 equivalent, roughly an 87% reduction. These are calculated from measured consumption and published warming factors, so the absolute numbers depend on those factors, but the comparison between flows is robust.