The role of the anaesthetist in mitigating the environmental impacts of nitrous oxide: a narrative review

Nitrous oxide (N2O) is a greenhouse gas (GHG) with ozone-depleting effects. It is a relatively minor, but important, measurable, and remediable part of healthcare’s contribution to global warming. Anaesthetists became aware of the GHG emissions associated with their daily work practices, particularly inhalation agents including N2O, well before other clinicians. However, only relatively recent research indicates that a significant amount of N2O is leaked before patient care, representing a much larger proportion of associated GHG emissions than clinical use. In addition, there are other sources of waste not related to clinical use. Consequently, while reduction of clinical use is important, it is not enough on its own. N2O is used in multiple clinical areas by various clinicians including in anaesthesia, midwifery and obstetrics, paediatrics, dentistry, and emergency medicine. There appears to be considerable geographic variation, and while evidence suggests that N2O use is declining in anaesthesia in some countries, it appears to be increasing in some countries in midwifery/obstetrics and paediatrics. Anaesthetists are leading efforts to reduce N2O usage, via mitigation of leaks (i.e. N2O waste before clinical use) and reduced clinical use. Engagement by anaesthetists with colleagues in midwifery/obstetrics and paediatrics appears to be at a formative stage. Further engagement with other specialties that use N2O will be necessary to reduce both leaks and clinical use. Safe and inexpensive alternatives to N2O, particularly in resource-constrained countries, will need ongoing consideration.