Southampton anaesthetists cut nitrous oxide use to help save the planet

Anaesthetists at University Hospital Southampton (UHS) NHS Foundation Trust are using less nitrous oxide – an anaesthetic with a big carbon footprint – to help the NHS reach net zero.

New research led by anaesthetist Dr Tom Pierce has shown that UHS has dramatically cut its use of nitrous oxide over the last 12 years, reducing its environmental impact. This provides a blueprint that could be adopted by Trusts across the UK.

Cutting down on nitrous oxide

The results, published in the journal Anaesthesia, show UHS cut its use of nitrous oxide between 2008 and 2020, resulting in a drop in carbon dioxide equivalent emissions from 2,125 to 448 tonnes annually.

This was made possible by the introduction of new equipment which enables anaesthetists to choose settings that use less nitrous oxide gas. These include new electronic anaesthesia workstations with a low flow setting that uses less of the gas, and more recently automated end-tidal control equipment, which monitors and automatically adjusts the amount given.

Whereas the previous equipment often delivered more nitrous oxide gas than was needed, the new technology enables anaesthetists to give just the right amount to effectively and safely anaesthetise patients.

A survey, conducted as part of the study, found 75% of the anaesthetists who responded used less nitrous oxide than they used to, mainly due to environmental concerns.

Overall, 77% thought climate change was very important or critical. While most anaesthetists who responded used nitrous oxide, they only used it for some patients. More than half did not consider nitrous oxide to be essential and thought it should not be freely available.

Big environmental impact

Nitrous oxide, also called laughing gas, has long been used as an anaesthetic. Although not used as much for general anaesthesia it is still used premixed with oxygen as Entonox in the Maternity Department, where it may be referred to as ‘gas and air’. It is the maternity use that is the focus for other researchers in the UK.

Nitrous oxide is a potent greenhouse gas, 265 times more powerful than carbon dioxide. This gives it a big environmental impact, accounting for about 5% of the carbon footprint of the NHS acute sector.

Due to its substantial carbon footprint, the NHS plans to reduce the use of nitrous oxide as part of its goal to be the world’s first net zero national health service. It aims to reach net zero by 2040 for the emissions it controls directly, including anaesthetics, and by 2045 for the emissions it can influence.

Dr Tom Pierce, Cardiac Anaesthetist and Environmental Advisor to the Royal College of Anaesthetists, said: “This study shows it is possible for an NHS Trust to reduce its use of nitrous oxide, with anaesthetists at UHS showing that they care about the environment and are doing what they can to protect it.

“Our results form a useful blueprint for other Trusts to help the NHS reach net zero. Further reductions in nitrous oxide use could be achieved with national strategies to develop and promote the use of alternatives and technologies to safely capture the exhaled gas.”

Continuing to invest in technology that reduces the impact UHS has on the environment is one of a number of initiatives contained in the UHS Green Plan, published by the Trust to coincide with World Earth Day (Friday 22 April).

The plan outlines actions that the Trust is committing to, and how it will be supporting its workforce to adopt changes that collectively work to reduce the carbon emissions generated by the organisation and its people. Working with patients and partners, UHS aims to deliver a healthier future by becoming carbon net zero.