Nitrous oxide in maternity: what’s all the gassing about?

Carbon footprinting in healthcare helps to inform us about carbon hotspots in our practice in order to seek and implement solutions. Knowledge and communication of the environmental impact of desflurane has resulted in a substantial reduction in use, from 23% of all volatile agents in 2018 to < 5% in 2022 [1]. However, recent interest in the greenhouse gas (GHG) impact of nitrous oxide for labour analgesia has been less well received. Why should discussing the environmental impact of nitrous oxide be such a taboo?

In the case of desflurane we have readily available alternatives; however this is not as straightforward when it comes to labour analgesia. A 2021 survey showed that nitrous oxide was used in 76% of births [2]. It has several advantages over other labour analgesics: it is available in all birth settings (mandated by NICE guidance); it does not require additional monitoring; and has relatively few side effects. There are currently no suitable inhalational analgesic alternatives that can be administered for prolonged periods. Even use of a birthing pool is contraindicated for many labouring women. Use of remifentanil and epidural analgesia require additional equipment, monitoring and staffing. In practice, the midwifery staffing crisis and recent supply issues with loss of resistance syringes, epidural giving sets, remifentanil and diamorphine challenge what we can offer safely. All of these factors mean that nitrous oxide is here to stay, and the onus rests with healthcare providers, not parturients, to reduce its GHG impact.

We must continue to improve access to a variety of labour analgesia options and provide education to help women make informed choices. With 75% of adults in the UK reportedly worried about climate change [3], it seems reasonable to provide user information about the environmental impact of healthcare. This work has already begun and the approach is hugely important. The National Childbirth Trust now mentions the environmental impact of Entonox® in their user information [4], exemplifying how this information can be presented sensitively to avoid making women feel guilty about their birth choices. The RCoA webpage Your anaesthetic and the environment uses infographics to help explain the carbon dioxide equivalence of different volatiles [5]; an example of how labour analgesics could be compared is presented in Figure 1.

There are ways to reduce GHG emissions whilst still offering Entonox to women in labour (Table 1). It is estimated that 40% of Entonox is lost as system waste via leaks in delivery systems or poor cylinder management [6]. Eliminating this wastage would be highly effective in reducing emissions, with no impact on women’s choice. Anaesthetists have a role to play in reducing emissions too. A 2021 survey demonstrated the impact of providing nitrous oxide as bridging analgesia via anaesthetic machines in obstetric theatres [7], which could simply be reduced using existing demand valve systems.

Table 1.

Scavenging and catalytic destruction can reduce environmental nitrous oxide levels by 70-80% [8], but require significant estates infrastructure and behaviour change to optimise both destruction efficiency and user/ staff acceptability. With no discernible ‘user benefit’, persuading organisations to invest thousands of pounds in such technology may be a hard sell. This is where increasing awareness, prioritising the financial and environmental benefits of reducing waste, plus pressure from Greener NHS and the wider public could be beneficial.

Scavenging and catalytic destruction can reduce environmental nitrous oxide levels by 70-80% [8], but require significant estates infrastructure and behaviour change to optimise both destruction efficiency and user/ staff acceptability. With no discernible ‘user benefit’, persuading organisations to invest thousands of pounds in such technology may be a hard sell. This is where increasing awareness, prioritising the financial and environmental benefits of reducing waste, plus pressure from Greener NHS and the wider public could be beneficial.

Fiona Pearson
Consultant Anaesthetist, South Tyneside and Sunderland NHS Foundation Trust

Emma Evans
Consultant Anaesthetist, St George’s University Hospitals NHS Foundation Trust

Twitter: @fi_pea; @DrEdebates

Figure 1. Infographic comparing carbon footprints of labour analgesics

References 

1. Greener NHS. Greener NHS Dashboard–volatile anaesthetic gases, 2022. https://tabanalytics.data.england.nhs.uk/#/workbooks/3237/views (accessed 26/11/2022). 
2. Care Quality Commission. Maternity survey, 2021. www.cqc.org.uk/publications/surveys/maternity-survey-2021 (accessed 26/11/2022). 
3. Office for National Statistics. Data on public attitudes to the environment and the impact of climate change, Great Britain, 2021. https://www.ons.gov.uk/peoplepopulationandcommunity/wellbeing/datasets/ dataonpublicattitudestotheenvironmentandtheimpactofclimatechangegreatbritain (accessed 26/11/2022). 
4. National Childbirth Trust. Labour pain relief: gas and air (Entonox), 2021. www.nct.org.uk/labour-birth/your-painrelief-options/labour-pain-relief-gas-and-air-entonox (accessed 26/11/2022). 
5. The Royal College of Anaesthetists. Your anaesthetic and the environment, 2022. https://rcoa.ac.uk/patient-information/about-anaesthesia-perioperative-care/your-anaesthetic-environment (accessed 26/11//2022).
6. NHS Scotland. Nitrous oxide mitigation implementation plan, Chakera A. 2022. https://www.publications.scot.nhs.uk/details.asp?PublicationID=7628 (accessed 26/11/2022). 
7. Pearson F, Lawson C, MacLennan K. Use of anaesthetic gases in obstetric anaesthesia: a survey of current practice. International Journal of Obstetric Anesthesia 2021; 48: 103215. 
8. Pinder A, Fang L, Fieldhouse A et al. Implementing nitrous oxide cracking technology in the labour ward to reduce occupational exposure and environmental emissions: a quality improvement study. Anaesthesia 2022; 77: 1228-36.

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