Exploring sevoflurane consumption and CO2 emissions of individual patients undergoing noncardiac surgery using a target-controlled sevoflurane administration system

Reduce sevoflurane consumption during anaesthesia remains an economic and environmental challenge. This case study analyzed retrospectively a large cohort of procedures using end-tidal (ET) Control to optimize sevoflurane consumption and assess the impact of ventilator settings on it. In single center, consecutive adult procedures for noncardiac surgery under general anaesthesia were analyzed in twelve operating rooms. The anaesthesia system (Aisys CS², GE, USA) was connected to software (Carestation Insight, GE, USA) that automatically recorded sevoflurane consumption for each case. Left to the discretion of the anaesthesiologist, fresh gas flow (FGF) was set at 0.5, 0.8 or 1 L.min^-1 with an initial end-tidal sevoflurane target of 1.2-2% to reach the goal of approximately 1.0 MAC. The primary endpoint was the sevoflurane consumption (mL.min^-1). Secondary endpoints were sevoflurane consumption and carbon footprint for the cohort (sevoflurane GWP₂₀ = 702) and by anaesthesia duration, type of airway management (endotracheal intubation EI, laryngeal mask LM), FGF and initial sevoflurane settings. From May to September 2024, 3064 procedures were recorded via the app. with a median (IQR) duration of surgery of 79 (47-124) minutes. Sevoflurane consumption was. 19 528 mL. Median (IQR) sevoflurane consumption was 0.16 (0.12-0.20) mL.min^-1 with a carbon footprint (sevoflurane GWP₂₀ including manufacturing = 1,468 kg/mL) of 0,23(0.17-0.29) kgCO_2eq.min^-1.Subgroup analysis demonstrated that FGF at 0.8 or 1.0 L.min^-1 significantly increased sevoflurane consumption and CO₂ emission when compared with 0.5 L.min^-1 (P < 0.01). Initial ET target sevoflurane levels of 1.2% vs greater than 1.2% did not change total sevoflurane consumption. Regarding airway management (EI vs LM), LM use was associated with higher consumption, specifically when duration > 120 min (P < 0.01). In this large cohort of cases, this study demonstrated that controlling ET with an FGF target of 0.5 L.min^-1 remained the best way to reduce sevoflurane consumption. Other settings did not significantly reduce gas consumption.