Journal watch13 January 2026
Author(s): L.F. Louro, C. Sinclair, L. Hargreaves, K. Coumbe, M. Hajeeh Ali, V. Percan, B. Bacon, A. Kukaswadia and T. Mair
Published in: Equine Veterinary Journal
Date: October 2025
DOI: https://doi.org/10.1111/evj.70108
Type of access: Requires membership/payment (click for full article)
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Our summary
Louro, L.F. et al. (2025) Multi-centre clinical audit of oxygen and inhalant anaesthetic usage in equine anaesthesia: The potential benefits of training and low-flow techniques. Equine Veterinary Journal.
The aim of this multi-centre clinical audit was to measure oxygen and isoflurane usage and calculate their associated global greenhouse gas (GHG) emissions, before and after implementation of low flow anaesthesia training.
The audit was performed on 5 equine referral hospitals in the UK before and after the introduction of a low flow anaesthesia training programme: period one (June-Sep 2022) and period 2 (June-Sep 2023). Anaesthesia training started at end of September 2022, and included in-house training, in addition to a series of webinars. The sessions included practical and theoretical teaching on all aspects of equine anaesthesia, with a focus on fostering a safety culture, carefully managing fresh gas flows during anaesthesia, minimising anaesthesia duration, and optimising pre- and intra-operative analgesia to reduce reliance on inhalant anaesthetics thereby reducing GHG emissions.
All hospitals used the same type of anaesthetic machine, isoflurane as the sole inhalant maintenance agent vaporised in 100% oxygen, and mechanical ventilation, although there were some variations in the anaesthetic protocols.
Data was collected from the horses’ anaesthetic records and included only on cases with both fresh gas flows and vapouriser settings recorded every 5 min. If one or both values were missing at a specific time point, that recording was excluded for that interval, while the rest of the data remained valid for analysis.
Retrospective data from 414 general anaesthetics (GA) were included in the audit, 219 and 195 GA in period 1 and period 2, respectively, with a total of 7251 5-min recordings, of which 7154 (98.6%) were complete. Data were analysed to calculate total oxygen and isoflurane usage throughout the entire anaesthetic period, as well as associated GHG emissions, and financial costs.
From period 1 and 2, results from the audit found an overall reduction in the use of oxygen and isoflurane corresponding to an overall reduction in GHG emissions of 9.6%. The reduction in the mean oxygen usage was statistically significant (from 396.3 ± 105.9 L/hr in period 1 to 338.1 ± 116.6 L/hr in period 2); while the reduction in isoflurane was not statistically significant (from 57.9 ± 16.3 mL/hr to 54.3 ± 20.5 mL/hr in period 2). However, when looking at the difference in the mean GHG emissions per hour of anaesthesia between 2 periods the reduction was not statistically significant (from 50.5 ± 14.2 kgCO2e to 47.4 ± 17.9 kgCO2e in period 2).
Based on a hypothetical usage scenario, assuming an initial fresh gas flow rate of 10 L/min for the first 15 min of anaesthesia to denitrogenate the anaesthetic circuit, followed by a reduced fresh gas flow rate of 2 L/min for the remainder of the procedure the usage of isoflurane usage would be 8.7 tCO2e, compared with the actual recorded emissions of 13.2 tCO2. This would correspond to a potential reduction in carbon emissions of up to 34.1%; and the associated reduction in oxygen and isoflurane offered a potential saving of over £1,300, over a 4-month period (Period 2).
Limitations of the study include missing data from a small number of GA records (97, 1.4%), and reliance on data accuracy and consistency collected retrospectively.
Take home
This clinical audit was carried out across 5 equine hospitals, demonstrated that implementing an anaesthesia training programme with low-flow techniques has the potential to reduce oxygen and inhalant anaesthetic use, resulting in both environmental and economic benefits.
The following may also be of interest
McMillan, M. (2021) Sustainable veterinary anaesthesia: single centre audit of oxygen and inhaled anaesthetic consumption and comparisons to a hypothetical model. Journal of Small Animal Practice, 62 (6), pp.420-427. https://doi.org/10.1111/jsap.13316
Elzahaby, D. et al. (2024) Inhalational anaesthetic agent consumption within a multidisciplinary veterinary teaching hospital: an environmental audit. Scientific reports, 14 (1), p. 17973.https://doi.org/10.1038/s41598-024-68157-5
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