Emergency Medicine Journal 2024

Original research Environmental impact of low-dose methoxyflurane versus nitrous oxide for analgesia: how green is the ‘green whistle’? Aleksis EV Martindale‍ ‍, 1 Daniel S Morris, 2,3 Thomas Cromarty, 4 Amarantha Fennell-Wells‍ ‍, 5 Brett Duane‍ ‍ 6,6

ABSTRACT Background The NHS has the target of reducing its carbon emission by 80% by 2032. Part of its strategy is using pharmaceuticals with a less harmful impact on the environment. Nitrous oxide is currently used widely within the NHS. Nitrous oxide, if released into the atmosphere, has a significant environmental impact. Methoxyflurane, delivered through the Penthrox ’green whistle’ device, is a short-acting analgesic and is thought to have a smaller environmental impact compared with nitrous oxide. Methods Life cycle impact assessment (LCIA) of all products and processes involved in the manufacture and use of Penthrox, using data from the manufacturer, online sources and LCIA inventory Ecoinvent. These data were analysed in OpenLCA. Impact data were compared with existing data on nitrous oxide and morphine sulfate. Results This LCIA found that Penthrox has a climate change effect of 0.84 kg carbon dioxide equivalent (CO 2 e). Raw materials and the production process contributed to majority of the impact of Penthrox across all categories with raw materials accounting for 34.40% of the total climate change impact. Penthrox has a climate change impact of 117.7 times less CO 2 e compared with Entonox. 7 mg of 100 mg/100 mL of intravenous morphine sulfate had a climate change effect of 0.01 kg CO 2 e. Conclusions This LCIA has shown that the overall ’cradle-to-grave’ environmental impact of Penthrox device is better than nitrous oxide when looking specifically at climate change impact. The climate change impact for an equivalent dose of intravenous morphine was even lower. Switching to the use of inhaled methoxyflurane instead of using nitrous oxide in certain clinical situations could help the NHS to reach its carbon emission reduction target. BACKGROUND The climate crisis is a health crisis. A recent report by Lancet Countdown, which tracks progress on health and climate change, discusses the unequiv- ocal contribution that ill-health and healthcare makes to rising global temperatures and vice versa. 1 In line with UK Government ambitions described in the Climate Change Act 2008, the Paris Agreement 2016 and the most recent Health and Social Care Act 2022 NHS England has set ambitious targets for carbon reduction. 2–4 The first goal is reducing NHS England’s prepandemic carbon emissions of 25 megatonnes of carbon dioxide equivalents

Handling editor Caroline Leech ► Additional supplemental material is published online only. To view, please visit the journal online (http://dx.doi. org/1 0.1136/e mermed-2022- 213042). 1 General Duties Medical Officer, 3 Medical Regiment, Catterick, UK 2 Ophthalmology, University Hospital of Wales, Cardiff, UK 3 Wilderness Medical Training, Wilderness Medical Training, Kendal, UK 4 Emergency Medicine, Southampton Children’s Hospital, Southampton, UK 5 Centre for Sustainable Healthcare, Centre for Sustainable Healthcare, Oxford, UK 6 Dental Science, Trinity College Dublin, Dublin, Ireland Correspondence to Capt Aleksis EV Martindale, Royal Army Medical Corps, Camberley GU15 4NP, UK; m artindalealeksis@gmail.c om Received 18 December 2022 Accepted 12 September 2023

(MtCO 2 e)—around 5% of England’s carbon foot- print—by 80% by 2032. 5 Of these 25 MtCO 2 e, 2% is attributable to anaesthetic gases. 6 Two recom- mendations are to be implemented to reduce these significant emissions: (1) altering clinical practice pertaining to prescribing and (2) administering and disposing of anaesthetic gases. Nitrous oxide (N 2 O), is a commonly used anaes- thetic gas in EDs in the UK and elsewhere. 7 Inhaled methoxyflurane can also be used in acute emergency care for analgesia during painful procedures and is superior in managing pain from trauma compared with standard analgesic treatments. 8 9 It is also thought to have a smaller overall environmental impact compared with N 2 O. We know that N 2 O has a 100-year global warming potential 66.25 times greater than methoxyflurane (N 2 O: 265, methoxy- flurane: 4) and is one of the six major greenhouse gases targeted by the Kyoto Protocol, however, the overall environmental impact of methoxyflurane is unknown. 10 ⇒ This type of analysis allows healthcare professionals and managers to make more informed decisions regarding procurement and delivering care, taking environmental impact into account. ⇒ The findings suggest a shift in the type of short- term analgesia used by clinicians to agents that are less harmful to the environment. WHAT IS ALREADY KNOWN ON THIS TOPIC ⇒ Nitrous oxide is frequently used for analgesia but has significant environmental impacts. ⇒ Inhaled methoxyflurane can be used as an analgesic agent in certain clinical settings. WHAT THIS STUDY ADDS ⇒ This life cycle impact analysis calculates the overall environmental impact of the currently available form of methoxyflurane, Penthrox. ⇒ Penthrox was found to have lower climate change impact by a factor of 117.7 for equivalent use of Entonox (nitrous oxide:oxygen, 50%:50%). ⇒ Morphine has the lowest climate change impact of the three analgesic agents. HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY

Published Online First 28 September 2023

► http://d x.d oi.o rg/1 0.1 136/ emermed-2 023-213432

To cite: Martindale AEV, Morris DS, Cromarty T, et al . Emerg Med J 2024; 41 :69–75. commercial re-use. See rights and permissions. Published by BMJ.

Martindale AEV, et al . Emerg Med J 2024; 41 :69–75. doi:10.1136/emermed-2022-213042