Decrease greenhouse gas pollution in anaesthesia
Anaesthesia is a carbon-intensive specialty, involving the routine use of inhaled drugs which are potent greenhouse gases. After patient use, these gases are exhausted directly to the environment, where they accumulate in the atmosphere contributing to global warming. Such inhaled anaesthetic drugs are volatile halogenated organic compounds (sevoflurane, desflurane, isoflurane, halothane) and nitrous oxide (N2O). The environmental impacts of desflurane and N2O are several times greater than the other inhaled anaesthetics, making them an even higher mitigation priority.
Volatile anaesthetic agents have been estimated to be responsible for 0.01 – 0.1% of total global CO2 equivalent (CO2e) emissions contributing to global warming; and based on atmospheric sampling of volatile agents, their accumulation is increasing (particularly desflurane). Whilst a seemingly small contribution to total global emissions, inhaled anaesthetics frequently account for 5% of acute hospital CO2e emissions, and 50% of perioperative department emissions (in high income countries). Their use is directly within the control of anaesthesia providers and thus, their stewardship is an important opportunity for greenhouse gas mitigation and leadership in healthcare environmental sustainability.
Anaesthesia practitioners to exercise stewardship in the use of volatile anaesthetic agents, when clinically safe to do so.
Actions to reduce inhaled anaesthetic atmospheric waste include:
1. Use lowest fresh gas flow rates during all stages of anaesthesia (e.g. <1L/minute during maintenance).
2. Avoid high impact inhaled anaesthetics: desflurane, nitrous oxide.
3. Decommission N2O central piping, and switch to portable tanks that remain closed between uses.
4. Consider intravenous and regional techniques, when safe to do so.
5. Measure inhaled anaesthetic greenhouse gas emissions at an institutional and provider level to support education, practice improvement and set targets for mitigation.
N.B. More research is needed before investing in waste anaesthetic gas (WAG) trapping (for volatiles only) or WAG destroying (N2O only) technology. While such technology appears promising, only a fraction of WAG is captured/re-processable for potential reuse. Further, reuse requires regulatory approval, and thus storage of reprocessed volatiles is presently required. Avoidance of these inhaled anaesthetics and reduction of fresh gas flows (FGFs) are much higher priorities.
1. Desflurane, which has a global warming potential over 100 years of 2540 CO2 equivalents (CO2e), was eliminated from the Yale New Haven Health System formulary in 2013 in favor of sevoflurane, saving an estimated US$1.2 million and 1.6 million kg CO2e (the equivalent of 360 passenger vehicles) annually from the flagship hospital alone.
2. In Australia and New Zealand, a network of anaesthesia trainees has formed a group to drive research and other initiatives around environmental sustainability in anaesthesia (TRA2SH – Trainee-led Research and Audit in Anaesthesia for Sustainability in Healthcare). This group has promoted an online pledge to encourage anaesthesia departments to immediately reduce their use of desflurane and remove it from their hospital formulary by 2025. Several large institutions, including The Alfred, Western Health and Fiona Stanley Hospital, have already removed desflurane from their formulary, along with many others who have pledged to do so prior to 2025 Link.
At the Fiona Stanley Hospital in Perth, the removal of desflurane from their formulary has saved approximately AUD$90 000 and approximately 300 tonnes CO2e per year (equivalent of 60 return flights from Perth to London). At Western Health in Melbourne, this same action has saved AUD$30 000 and reduced emissions by 140 tonnes per year (the equivalent of 36 return flights from Melbourne to London). Following their action in 2021, The Alfred Hospital reported only positive, supportive departmental feedback Link.
3. After labelling on environmental impact at the point of use, desflurane use at the University of Wisconsin was reduced by 55% in favour of sevoflurane. This resulted in a saving of $25,000/month in 2015, and an average reduction of per anaesthetic case emissions from 163kg CO2e pre-intervention to 58kg CO2e post-intervention. Link
4. The University of California San Francisco implemented an electronic clinical decision support tool, aimed at nudging providers to reduce FGFs in real-time. The electronic health record tool alerts providers if FGFs > 0.7 L/min for desflurane, and >1 L/min for sevoflurane, during maintenance anaesthesia. In 2018, researchers demonstrated reductions in mean FGFs by 0.6 L/min for sevoflurane and 0.2 L/min for desflurane.
5. The primary driver of N2O emissions is loss of gas in the facility infrastructure. In 2019, Providence St. Vincent hospital in Portland, Oregon, USA, procured 991 metric tons of N2O. Investigators discovered infrastructure leak rates, ranging from <0.1 L/min to >3.5 L/min, resulting in use efficiency of 5-40%. Central piped N2O was subsequently decommissioned, and portable e-cylinders substituted, saving 958 metric tonnes of CO2e of N2O annually, equivalent to 2,407,644 fewer car miles driven, and $12,000 in procurement costs.
6. In 2020, Lothian NHS Scotland demonstrated system losses from 3 centrally piped N2O systems across two hospital sites, of approximately 790,000 and 685,000 litres, respectively. Mitigation activities, including fully decommissioning centrally piped N2O, eliminated the equivalent of 806 tonnes CO2e per annum. The national Nitrous Oxide Project was subsequently launched in January 2021. By the end of March 2021, 16 hospitals across the NHS reported an annual system loss of 13,770,000 litres, 95% of total procured N2O. This is equivalent to 7,219 tonnes CO2e, comparable to 7,600 flights from Paris to New York.
Supporting consensus guideline from the World Federation of Societies of Anaesthesiologists (WFSA):
White et al. (2021), ‘Principles of environmentally-sustainable anaesthesia: a global consensus statement from the World Federation of Societies of Anaesthesiologists’, Anaesthesia, 77(2), 201-212 Link
Comprehensive review of basic science and anaesthesia sustainability literature:
McGain, Muret, Lawson & Sherman (2020), ‘Environmental Sustainability in Anaesthesia and Critical Care’, British Journal of Anaesthesia, 125(5):680-692 Link
Checklists to improve environmental sustainability in perioperative environments:
The ASA Sustainability Checklist: Link
The ANZCA Environmental Sustainability Audit Tool: Link
Calculate the comparative CO2e emissions associated with different anaesthesia methods:
Yale Gassing Greener App (free), provider educational calculator: Link
American Society of Anesthesiologists (free), institutional calculator: Link
AAGBI Anaesthetic Impact Calculator (free), provider calculator: available as an app Link or spreadsheet Link
Further information and resources about the comparative environmental impact of desflurane and N2O:
The greenhouse gas emissions (CO2e) for desflurane as clinically used are approximately 50 times that of sevoflurane and isoflurane over a 100-year period. Desflurane is also significantly more costly and lacks evidence of improved clinical outcomes over alternative anaesthetics.
Sherman, Le, Lamers & Eckelman. (2012) Life Cycle Greenhouse Gas Emissions of Anaesthetic Drugs, Anaesthesia and Analgesia, 114(5), 1086-90 Link
Sherman, Feldman, Chesebro (2020), ‘Inhaled Anesthetic 2020 Challenge: Reduce your Inhaled Carbon Emissions by 50%!”, ASA Monitor, 84, 14-17: Link
Sherman & Berkow (2019), ‘Scaling Up Inhaled Anesthetic Practice Improvement: The Role of Environmental Sustainability Metrics’, Anesthesia & Analgesia, 128(6), 1060-1062, Link
McGain et al. Why be sustainable? The ANZCA Professional Document PS64: Statement on Environmental Sustainability in Anaesthesia and Pain Medicine. Anaesth Intens Care 2019 Sep;47(5):413-422 Link
N2O is less potent and must be used in high concentrations (typically 50%) and has a very long atmospheric lifetime (114 years). Therefore, its warming impacts are similar to desflurane in clinically relevant doses.
Sherman, Le, Lamers & Eckelman. (2012) ‘Life Cycle Greenhouse Gas Emissions of Anaesthetic Drugs’, Anaesthesia and Analgesia, 114(5), 1086-90 Link
Association of Anaesthetists ‘Nitrous Oxide Project’: Link
Seglenieks R et al. (2022) ‘Discrepancy between procurement and clinical use of nitrous oxide: waste not, want not’, British Journal of Anaesthesia, 128(1):e32-e34 Link
Further information about low flow anaesthesia:
There have been historical concerns about a theoretical risk of renal injury associated with ‘compound A’ production when sevoflurane is used with low FGFs. There is no clinical evidence of harm associated with compound A in humans and it is advised that sevoflurane can safely be used with low FGFs to minimise its environmental impact. It is recommended to use CO2 absorbers which contain low or no sodium hydroxide (NaOH) during low FGF anaesthesia with sevoflurane.
Feldman (2012), ‘Managing fresh gas flow to reduce environmental contamination’, Anaesthesia and Analgesia, 114(5):1093-101 Link
Sondekoppam et al. (2020), ‘The impact of sevoflurane anesthesia on postoperative renal function: a systematic review and meta-analysis of randomized-controlled trials’, Canadian Journal of Anaesthesia, 67(11):1595-1623 Link
Environmental impact and use of total intravenous anaesthesia (TIVA):
The environmental impact of TIVA is substantially less than volatile anaesthesia, even when consumables and the carbon cost of production is factored in.
Sherman and Barrick (2019), ‘Total Intravenous Anesthetic Versus Inhaled Anesthetic: Pick Your Poison’, Anesthesia and Analgesia, 128(1):13-15. Link
Environmental impact of regional anaesthesia:
The use of regional anaesthesia is not a default low carbon alternative and consideration needs to be given to minimising O2 flows, reducing single use plastics and sources of energy generation, to minimise its impact.
McGain et al. (2021), ‘Carbon Footprint of General, Regional, and Combined Anesthesia for Total Knee Replacements’, Anaesthesiology, 135(6):976-991 Link
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