Sevoflurane usage and fresh gas flows in Maquet anaesthetic machines at an academic hospital

Abstract

Background: Low-flow anaesthesia (LFA) is crucial in combating rising healthcare costs and the global threat of climate change. This study analysed the conduct of inhalational anaesthesia at a Johannesburg Academic Hospital to determine fresh gas flows (FGF) and liquid agent consumption (LAC) at various stages of anaesthesia.

Methods: A prospective, contextual research design was followed. Purposive sampling method was used in 10 theatres equipped with Maquet Flow-i® anaesthetic machines. Calculated LAC values were compared to those measured by the anaesthetic machines.

Results: The average FGF during induction, maintenance and time-weighted case average were 7.07 L/min, 1.41 L/min and 1.73 L/min, respectively. The average end-tidal sevoflurane concentration during maintenance was 2.40%. The calculated average LAC for induction, maintenance and total case were 7.74 mL, 28.01 mL and 36.84 mL, respectively, while the hourly LAC was 16.71 mL/h. The calculated case average LAC overestimated the measured values by 4.14 ± 4.86 mL (12.98%), with 98.5% of values being within ± 1.96 standard deviation (s.d.). Despite its brevity, the induction phase accounted for 21% of the calculated LAC. The calculated liquid agent expenditure over time was ZAR54.32 ± 23.55/h. Case average FGF had a very high positive correlation with the calculated cost of sevoflurane, r = 0.86, p < 0.001.

Conclusion: This study demonstrated that the prevailing use of medium-flow anaesthesia among anaesthetists at our institution resulted in significant sevoflurane wastage, increased expenditure and environmental pollution.

Contribution: The study provides insight into anaesthesia practices at an academic hospital. It highlights the need to implement policies to standardise LFA as a cost-saving and environmentally friendly strategy.