Anesthesia & the Environment
It's Time to Choose Greener Gases
Climate change is the single greatest risk to global health.
Climate change has been recognized as a significant global health threat of the century, with recent reports from the Intergovernmental Panel on Climate Change (IPCC) predicting that global warming will exceed 1.5°C thresholds by 2040. In recognition of the widespread social, economic, and health consequences of climate change, Canada has signed onto the WHO COP26 Health Programme in November 2021. This agreement, shared by 50 countries, commits Canada to develop climate-resilient and low-carbon, sustainable healthcare systems. Currently, Canada has the third highest per-capita healthcare emissions, which account for 4.6% of national emissions.
More than ever before, we have seen the devastating impact of heatwaves, floods, wildfires, food insecurity, and forced displacement of people around the world. As physicians, we have a duty to advocate for the health of our environment, because it directly affects the health of our patients.
Modern anesthetic agents are known greenhouse gases
Modern anesthetic agents are known greenhouse gases with hundreds to thousands of times the global warming impact compared to carbon dioxide (CO2). Less than 5% of halogenated anesthetic gases are metabolized by the body, and the remainder is removed by OR waste gas scavenging systems that pump the gas virtually unchanged into the atmosphere. Desflurane and nitrous oxide are common anesthetic volatile agents with particularly harmful environmental impacts. Desflurane has a notably high global warming potential (GWP), which is a measure of the infrared radiation absorbed by a greenhouse gas over a period of time expressed relative to CO2. While the 100-year GWP (GWP100) of CO2 is equal to 1 by definition, the GWP100 of sevoflurane, desflurane, and nitrous oxide are 130, 2540, and 298 respectively, and these gases have an atmospheric lifespan of 1.1, 14, and 114 years respectively. Nitrous oxide additionally directly depletes the ozone layer, which protects the Earth from harmful UV-B radiation from the sun.
Desflurane vs Sevoflurane
The climate impact of an anesthetic gas also depends on the amount of gas required to provide adequate anesthesia. This measure is determined by the potency of the gas, the minimum alveolar concentration (MAC), and the fresh gas flow (FGF) at which the gas can be used. The greenhouse gas effect of an anesthetic gas, taking into account GWP and amount of gas used, is commonly expressed as carbon dioxide equivalent (CDE). When used at a FGF of 1 L/min at 1 MAC-hour, the 100-year CDE of desflurane is fifty times greater than that of sevoflurane. Minimizing the use of desflurane is thus an important strategy for decreasing anesthetic emissions. Indeed, a study of three hospitals in Canada, the UK, and the US found that anesthetic agents were the greatest source of OR gas emissions in hospitals where desflurane was routinely used.
In addition to environmental benefits, sevoflurane is often cheaper. Reducing desflurane has been associated with savings of as much as $25,000 USD per month, as reported at the University of Wisconsin.
Given the harms of desflurane, some Canadian institutions, including in London, Vancouver, and Toronto have begun to phase down its use, while other systems such as Health Sciences North in Sudbury, Ontario or the Yale-New Haven Health System in the United States have eliminated it entirely from their hospital formularies.
The American Society of Anesthesiologists (ASA) has also recommended a number of strategies, including utilizing low fresh gas flows, avoiding high impact inhaled anesthetics including nitrous oxide, using intravenous and regional anesthetic techniques, and investing in waste anesthetic gas trapping or destroying technology. More information on these suggestions can be found in their report, Greening the Operating Room and Perioperative Arena: Environmental Sustainability for Anesthesia Practice, produced by the ASA Task Force on Environmental Sustainability Committee on Equipment and Facilities.
Reducing desflurane use can be challenging when there are established practice patterns, limited resources, or competing priorities. To help alleviate some of the initial work in promoting volatile agent change, we have created a Greener Gases Starter Pack that contains the resources developed by the Greener Gases project at McMaster University. This project was started in August 2020 as part of the Canadian Federation of Medical Students inaugural Project Green Healthcare cohort, and it was publicly launched in February 2021. Although we are still in the first year of project implementation and data collection is currently underway, the urgency of climate action compels us to share the resources we developed to help Canadian healthcare institutions shift to reduce desflurane use and help meet the mandate of the COP26 Health Programme.
Our starter pack includes a white paper of up-to-date evidence, a PowerPoint presentation introducing the project, anesthetic machine labels, and infographic posters for high-traffic areas such as the anesthesia lounge. The package also includes a provider survey to help evaluate attitudes, knowledge, and beliefs pre- and post-intervention, as well as an easy-to-read narrative guide describing tips, recommendations, and lessons learned.
In releasing this starter pack, we recognize that reducing desflurane use is only the first step to improving anesthetic sustainability. Other strategies include the installation of desflurane capture and recycle technologies, desflurane and nitrous oxide elimination, increase in total intravenous anesthesia and regional technique use, and the consistent use of low-flow anesthesia. A comprehensive list of recommendations can be found at the American Society of Anesthesia’s Greening the Operating Room guidelines (see above).
Join the Movement
Use our free Starter Pack: a collection of resources including an infographic, white paper, powerpoints, and anesthesia machine labels, to create local change at your institution today.