Abandoning inhalational anaesthesia

Abstract

The 2018 Intergovernmental Panel on Climate Change (IPCC) Special Report Global Warming of 1.5°C (SR15) makes sobering reading 1. At the current rate, global warming is likely to reach 1.5°C above pre-industrial levels between 2030 and 2052, and this is likely to result in far-reaching effects, including: climate change; sea level rise; loss of biodiversity; global health problems; food and water shortage; mass migration; and geopolitical insecurity. Adaptation to these challenges remains possible below a rise of 1.5°C, but would become increasingly difficult towards 2°C and beyond, as 'tipping points' are exceeded. Limiting global warming to 1.5°C will require global net emissions of carbon dioxide to fall by approximately 45% from 2010 levels by 2030, reaching 'net zero' around 2050 1. These targets are much more stringent than those agreed by the 1998 Kyoto Protocol 2, exceed the scope of the 2015 Paris Agreement 3 and will require 'rapid and far reaching' co-operative global socio-economic changes, including: shifts to renewable energy; changes to food systems; transport electrification; urban restructuring; and carbon capture. Independent consensus supports the immediacy of the changes needed 4. Inhalational anaesthetic agents are fluorocarbons that contribute to man-made climate change primarily through 'radiative forcing' (i.e. acting like greenhouse gases), but also through the carbon cost of their life cycle (manufacture, storage, transport, use and recovery). Their global warming potentials can be compared with that of carbon dioxide over a given time period (usually 20 years or 100 years). Desflurane has the highest global warming potential (one 240-ml bottle of vaporised desflurane being equivalent to the global warming effect of 1296 kg CO2 over 20 years), much higher than that of isoflurane and sevoflurane (521 kg and 132 kg CO2 equivalents (CO2e).250ml−1 bottle, respectively) 5-7. Currently, the global market for inhalational anaesthetic agents is ~12.5 million bottles (worth US$1.12 billion), a figure projected to rise to ~14.9 million bottles by 2025 (worth $1.34 billion) 8. Sevoflurane is the market leader (sevoflurane 70%, desflurane 20%, isoflurane 10%). From these figures, and assuming negligible recovery or metabolism, the estimated annual contribution of inhalational anaesthetic agents represents ~ 0.01% of global CO2 production (0.005/37.1 Gt CO2e) 9. Although a relatively small proportion, this is equivalent to flying an average commercial airliner ~418 times around the world. The NHS Sustainable Development Unit has estimated that anaesthetic gases (including nitrous oxide) contribute ~5% of the carbon footprint of UK hospitals (~0.56/10.4 million tons CO2e; ~0.08 mt (~0.8%) inhalational anaesthetic agents only) 10. An anaesthetist using low-flow (< 0.5 l.min−1) 6% desflurane in 50/50 air/O2 after intravenous induction in theatres without scavenging, uses ~60 ml desflurane during a 7-h operating list 11. If the gases are vented to the atmosphere (as is invariably the case), this is equivalent to ~ 325 kg CO2 (GWP20). Assuming three lists.week−1, 45 weeks.year−1, over a 40-year career, that anaesthetist would have been responsible for releasing 1755 tons CO2e; this is equivalent to ~880 return passenger flights between London Heathrow and JFK airports, ~ 22.year−1 or one trans-Atlantic flight for every week of work. The Association of Anaesthetists has done much to raise professional awareness about the environmental impacts of using inhalational anaesthetic agents and how to mitigate these [https://anaesthetists.org/Home/Resources-publications/Environment], and recently supported the NHS 'Clean Air' day [https://anaesthetists.org/Home/Resources-publications/Environment/Clean-Air-Day-2019]. Similarly, the Royal College of Anaesthetists has recently committed to minimising the environmental effects of anaesthesia, but without specifically addressing the impact of inhalational anaesthetic agents 12. Other authors have called for enhanced awareness of the environmental harms of inhalational agents and reductions in their use through low-flow anaesthesia 13 and the capture and reprocessing of exhaled vapours 14. However, even if these technologies were universally available and affordable, atmospheric escape of inhalational agents would continue to occur. Instead, given the urgency required to avoid the imminent climate catastrophe identified by the IPCC, we argue that it is 'too late to mitigate': the profession of anaesthesia must consider specifically abandoning the use of inhalational anaesthetic agents by 2030. Given their environmental impact, it is perhaps surprising that the use of inhalational anaesthetic agents has not been addressed by either international climate agreements or national carbon reduction strategies, to date. Neither the Montreal Protocol and Kigali Amendment (dealing with ozone depletion) nor the Kyoto Protocol and Paris Agreement mention inhalational anaesthe