CVS Equine referral hospitals deliver major cuts in isoflurane use and carbon emissions through innovative anaesthesia practices
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CVS is taking a major step toward greener veterinary care with new findings showing substantial reductions in Isoflurane consumption and associated greenhouse gas emissions across its Equine referral hospitals.

The initiative - delivered across five CVS equine referral hospital sites - has been led by Luís Filipe Louro, EBVS Specialist in Veterinary Anaesthesia and Analgesia at CVS Chestergates Veterinary Specialists, a CVS companion animal referral centre in Chester.

Isoflurane, a widely used and volatile anaesthetic agent in equine surgery, is also a potent greenhouse gas (GHG). When released into the atmosphere, volatile anaesthetics contribute to climate change, with Isoflurane possessing a global warming potential many hundreds of times greater than carbon dioxide. For this reason, anaesthetic gases are increasingly recognised as a key opportunity for reducing emissions across human and veterinary healthcare.

Recognising this, CVS Equine set out to understand current anaesthetic gas use and identify practical ways to reduce environmental impact while maintaining the highest standards of patient care. Working collaboratively with the equine division, Luís Filipe Louro designed and implemented a structured multicentre clinical audit spanning June-September 2022 (pre‑intervention) and June-September 2023 (post‑intervention).

The project included five CVS Equine referral hospitals and analysed 414 general anaesthetic procedures across the two audit periods. The training programme focused on optimising fresh gas flow rates, improving analgesia, and promoting the safe and effective use of low‑flow anaesthesia - an established technique in human medicine that reduces wastage of oxygen and volatile agents.

The clinical audit revealed a clear shift in anaesthetic practice, resulting in meaningful institutional environmental gains. Across the five hospitals, total Isoflurane usage decreased by 9.6% and oxygen usage by 17.9% between the two audit periods. This resulted in an overall reduction in GHG emissions from anaesthetic gases of 9.6%, falling from 14.6 to 13.2 tonnes of CO₂e over the four-month study periods. Statistical analysis identified several key factors influencing GHG emissions per anaesthetic case, including the period prior and post-training, total oxygen usage, anaesthesia duration, average isoflurane vaporiser setting, and the interaction between oxygen usage and study period. After adjusting for case mix and other variables, cases performed during the second study period were associated with lower GHG emissions per case compared with those in the first period.

The study also explored a hypothetical low-flow anaesthesia model, based on an initial short period of high fresh gas flow followed by maintenance at 2 L/min. Modelling suggested that, if consistently applied, such an approach could reduce anaesthetic gas-related emissions by up to 34% compared with current practice, highlighting further potential for improvement.

A central aspect of the programme was ensuring that reducing fresh gas flows did not compromise patient safety. All hospitals used multiparameter monitoring - including inspired and expired oxygen levels - allowing anaesthetists to confidently maintain safe FiO₂ levels throughout procedures. These findings show that low‑flow anaesthesia can be implemented responsibly and effectively in equine practice.

Speaking about the initiative, Luís Filipe Louro said:

Our results highlight the enormous potential for veterinary teams to reduce anaesthetic gas emissions through structured training, regular equipment checks, and a shift towards evidence‑based low‑flow techniques. It shows we can become significantly more sustainable without compromising safety. By embedding sustainable anaesthesia practices across our equine referral network, CVS is demonstrating how veterinary groups can take meaningful action on climate responsibility. Our group now plans to extend this work further, supporting its equine hospitals to adopt low‑flow anaesthesia consistently, invest in efficient anaesthetic equipment and encouraging wider profession‑wide engagement. I’m incredibly proud of the CVS Equine teams for embracing this work and demonstrating what is possible.
CVS Group operates across small animal, farm animal, equine and laboratories, with over 500 veterinary practices and referral centres in the UK and Australia. CVS has invested £122 million in its sites, facilities, equipment and technology since the start of 2023, in addition to providing industry leading training and support, to give the best possible care to animals.