Multi-centre clinical audit of oxygen and inhalant anaesthetic usage in equine anaesthesia: The potential benefits of training and low-flow techniques.

Background: The healthcare sector contributes significantly to global greenhouse gas (GHG) emissions, with anaesthetic gases being a notable contributor. Implementing sustainable practices in equine anaesthesia, such as low-flow anaesthesia, offers potential benefits.

Objectives: To audit oxygen and isoflurane usage in five equine hospitals, their associated GHG emissions, and the impact of anaesthesia training on mitigating these emissions.

Study design: Multi-centre clinical audit.

Methods: This audit covered two periods: study period one (1 June-30 September 2022) and study period two (1 June-30 September 2023). After period one, an anaesthesia training programme introduced low-flow techniques. Data collected retrospectively included patient signalment, anaesthetic protocol, and 5-min recordings of fresh gas flow (FGF) and vapouriser settings. GHG emissions (in carbon dioxide equivalents) and costs (in £) were calculated. Statistical analysis used a linear mixed-effects model with a significance level of p-value <0.05.

Results: A total of 414 general anaesthetics were audited. Between study period one and two, isoflurane and oxygen usage decreased by 9.6% and 17.9%, respectively, resulting in a 9.6% reduction in GHG emissions (from 14.6 to 13.2 tCO₂e). A linear mixed-effects model identified five significant predictors of GHG emissions per case: study period, oxygen usage, anaesthesia duration, average isoflurane vapouriser setting, and the interaction between oxygen usage and study period. Cases in study period two were associated with lower GHG emissions, producing on average 10.4 kgCO₂e less per case (p = 0.01), while each additional litre of oxygen consumed increased emissions by 0.12 kgCO₂e (p < 0.001).

Main limitations: Missing data from FGF and/or vapouriser settings and the minimal variability between hospitals could be perceived as limitations.

Conclusions: This audit demonstrates that practising low-flow anaesthesia can effectively reduce the environmental impact of inhalant anaesthetic agents during equine anaesthesia. Wider adoption could improve sustainability, although further research and broader professional engagement are needed.