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

## TL;DR

This study examines how anesthetists use sevoflurane and fresh gas flows at an academic hospital, finding that higher flows increase costs and environmental impact.

## Contribution

The study provides empirical evidence on sevoflurane usage and fresh gas flows in clinical practice, highlighting inefficiencies and environmental implications.

## Key findings

- Medium-flow anesthesia was prevalent, leading to significant sevoflurane wastage and increased costs.
- Induction phase accounted for 21% of sevoflurane consumption despite being brief.
- Case average fresh gas flows correlated strongly with sevoflurane costs (r = 0.86).

## Abstract

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.

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.

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.

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.

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.