Abstract and Introduction
With an estimated worldwide volume of 266 million surgeries in 2015, the call for general inhalation anesthesia is considerable. However, widely used volatile anesthetics such as N2O and the highly fluorinated gases sevoflurane, desflurane, and isoflurane are greenhouse gases, ozone-depleting agents, or both. Because these agents undergo minimal metabolism in the body during clinical use and are primarily (≥95%) eliminated unchanged via exhalation, waste anesthetic gases (WAGs) in operating rooms and postanesthesia care units can pose a challenge for overall elimination and occupational exposure. The chemical properties and global warming impacts of these gases vary, with atmospheric lifetimes of 1–5 years for sevoflurane, 3–6 years for isoflurane, 9–21 years for desflurane, and 114 years for N2O. Additionally, the use of N2O as a carrier gas for the inhalation anesthetics and as a supplement to intravenous (IV) anesthetics further contributes to these impacts. At the same time, unscavenged WAGs can result in chronic occupational exposure of health care workers to potential associated adverse health effects. Few adverse effects associated with WAGs have been documented, however, when workplace exposure limits are implemented. Specific measures that can help reduce occupational exposure and the environmental impact of inhaled anesthetics include efficient ventilation and scavenging systems, regular monitoring of airborne concentrations of waste gases to remain below recommended limits, ensuring that anesthesia equipment is well maintained, avoiding desflurane and N2O if possible, and minimizing fresh gas flow rates (eg, use of low-flow anesthesia). One alternative to volatile anesthetics may be total intravenous anesthesia (TIVA). While TIVA is not associated with the risks of occupational exposure or atmospheric pollution that are inherent to volatile anesthetic gases, clinical considerations should be weighed in the choice of agent. Appropriate procedures for the disposal of IV anesthetics must be followed to minimize any potential for negative environmental effects. Overall, although their contributions are relatively low compared with those of other human-produced substances, inhaled anesthetics are intrinsically potent greenhouse gases and pose a risk to operating-room personnel if not properly managed and scavenged. Factors to reduce waste and minimize the future impact of these substances should be considered.
Since the 1950s, the climate system has warmed, causing changes that are projected to have an increasing effect on environmental and social determinants of health such as the need for clean air, safe drinking water, sufficient food, and secure shelter.[1,2] According to a 2014 report by the World Health Organization (WHO), such effects are expected to cause an additional 250,000 deaths/y in the coming decades. With the human influence on global climate becoming clearer over the last several decades, integrated evidence-based responses from individuals, institutions, and governments are needed more than ever to mitigate the ecological and health effects of climate change. A key contributor to climate change is the emission of greenhouse gases (GHGs),[1,3] which includes release of waste anesthetic gases (WAGs) from surgical procedures into the environment (Figure 1). Although anesthesia gases contribute a relatively small portion of GHGs, a strong body of evidence supports the importance of minimizing WAG release into the environment to limit contributions to climate change and associated health risks on the global level and, on an individual level, to minimize occupational exposure and risk of adverse effects.
The total annual US GHG emission in 2012 was 6.2 gigatons of CO2 equivalent, of which 6.8% comprised N2O (4.3%) and fluorinated gases (3%; hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride, and nitrogen trifluoride).4 The contributions of inhaled anesthetics (N2O, desflurane, isoflurane, and sevoflurane) to US GHG emissions for 2011–2013 were estimated to be 5.6 million tons of CO2 equivalent (excluding dental, laboratory, and veterinary medicine),5,6 comprising approximately 1% of GHG emissions from the US health care sector6 and approximately 0.1% of total US GHG emissions.4,6 GHG indicates greenhouse gas.
The importance of this issue is further supported by the considerable worldwide volume of surgical procedures, many of which call for general inhalation anesthesia. A 2019 study of global surgery metrics estimated that 266 million surgeries were performed worldwide in 2015, with a global median of 4171 procedures per 100,000 individuals. Just in the United States, an estimated 36 million surgeries were performed in 2015, corresponding to 11,113 surgeries per 100,000 individuals. This large surgical volume exposes a broad range of health care workers, including anesthesiologists, dentists/dental personnel, nurse anesthetists, operating-room nurses, operating-room technicians/personnel, recovery-room nurses/personnel, and surgeons, to volatile anesthetics. In the United States alone, during 2015, more than a quarter of a million health care workers were potentially exposed to anesthetic gases that leak during procedures (ie, WAGs) and are consequently at risk for associated adverse health effects.
Given these considerations, this narrative review aimed to summarize the current understanding of the environmental (climate change health effects, greenhouse effect/gases that impact the atmosphere, and effect of anesthetic gases released into the atmosphere) and occupational (agents used, early research on exposure and health impact, exposure limits, and modern exposure and health effects) exposure aspects of volatile anesthetic gases. In this context, specific strategies and recent innovations for hospital anesthesia waste-minimization efforts are also discussed (volatile/inhaled and intravenous [IV] anesthetic alternatives and current strategies to minimize environmental and occupational exposure, including "greening the operating room/operating theater").
Anesth Analg. 2021;133(4):826-835. © 2021 International Anesthesia Research Society