Carbon Footprint of General, Regional, and Combined Anesthesia for Total Knee Replacements

Forbes McGain, F.A.N.Z.C.A, F.C.I.C.M., Ph.D.; Nicole Sheridan, F.A.N.Z.C.A.; Kasun Wickramarachchi, B.Sc., M.P.H., M.D.; Simon Yates, M.D., Brandon Chan, M.B.B.S.; Scott McAlister, B.Sc., P.grad., Dip.Sci., M.Eng.Sci.


Anesthesiology. 2021;135(6):976-991. 

In This Article

Abstract and Introduction


Background: Health care itself contributes to climate change. Anesthesia is a "carbon hotspot," yet few data exist to compare anesthetic choices. The authors examined the carbon dioxide equivalent emissions associated with general anesthesia, spinal anesthesia, and combined (general and spinal anesthesia) during a total knee replacement.

Methods: A prospective life cycle assessment of 10 patients in each of three groups undergoing knee replacements was conducted in Melbourne, Australia. The authors collected input data for anesthetic items, gases, and drugs, and electricity for patient warming and anesthetic machine. Sevoflurane or propofol was used for general anesthesia. Life cycle assessment software was used to convert inputs to their carbon footprint (in kilogram carbon dioxide equivalent emissions), with modeled international comparisons.

Results: Twenty-nine patients were studied. The carbon dioxide equivalent emissions for general anesthesia were an average 14.9 (95% CI, 9.7 to 22.5) kg carbon dioxide equivalent emissions; spinal anesthesia, 16.9 (95% CI, 13.2 to 20.5) kg carbon dioxide equivalent; and for combined anesthesia, 18.5 (95% CI, 12.5 to 27.3) kg carbon dioxide equivalent. Major sources of carbon dioxide equivalent emissions across all approaches were as follows: electricity for the patient air warmer (average at least 2.5 kg carbon dioxide equivalent [20% total]), single-use items, 3.6 (general anesthesia), 3.4 (spinal), and 4.3 (combined) kg carbon dioxide equivalent emissions, respectively (approximately 25% total). For the general anesthesia and combined groups, sevoflurane contributed an average 4.7 kg carbon dioxide equivalent (35% total) and 3.1 kg carbon dioxide equivalent (19%), respectively. For spinal and combined, washing and sterilizing reusable items contributed 4.5 kg carbon dioxide equivalent (29% total) and 4.1 kg carbon dioxide equivalent (24%) emissions, respectively. Oxygen use was important to the spinal anesthetic carbon footprint (2.8 kg carbon dioxide equivalent, 18%). Modeling showed that intercountry carbon dioxide equivalent emission variability was less than intragroup variability (minimum/maximum).

Conclusions: All anesthetic approaches had similar carbon footprints (desflurane and nitrous oxide were not used for general anesthesia). Rather than spinal being a default low carbon approach, several choices determine the final carbon footprint: using low-flow anesthesia/total intravenous anesthesia, reducing single-use plastics, reducing oxygen flows, and collaborating with engineers to augment energy efficiency/renewable electricity.


Climate change has become a considerable healthcare threat of the 21st century,[1] yet health care itself produces greenhouse gases directly (electricity and gas), but also from indirect emissions associated with consumption of goods and services.[2,3] The Australian healthcare system is responsible for approximately 7% of the total Australian greenhouse gas emissions.[4] Within hospitals, the intensive care unit[5] and operating rooms[6] are the most demanding of natural and financial resources. Operating rooms require large amounts of medical equipment, produce much waste,[7] and have large energy requirements.[6,8] As climate change has become an environmental (and health) emergency,[1] health systems need to investigate ways in which high-quality health care can be delivered while minimizing the environmental impact.

MacNeill et al.[6] studied three hospitals, one each in Canada, the United States, and the United Kingdom, finding that anesthesia could have greater carbon dioxide equivalent emissions than (1) all surgical equipment and procurement, and (2) all operating room–associated energy requirements including heating, ventilation, and air conditioning.[6] Multiple studies have focused on the surgical side of carbon dioxide equivalent emissions for different operations (e.g., hysterectomies,[8] cesareans,[9] and cataracts[10]). The carbon dioxide equivalent emissions associated with the anesthetic gases desflurane and nitrous oxide are significant.[11] Similar to the United Kingdom hospital in the study by MacNeill et al.,[6] we observed minimal desflurane and nitrous oxide use in our hospital, although we recognize variability in Australian anesthetic practice.[12] There are calls for studies to investigate the effects of general versus regional anesthetic choice upon carbon dioxide equivalent emissions,[13] as this could be important even in the absence of desflurane or nitrous oxide.

We asked what was the carbon footprint of the anesthetic component of a total knee replacement, a common operation for which there is clinical equipoise between alternate anesthetic approaches. We aimed to quantify the carbon dioxide equivalent emissions of general anesthesia, spinal anesthesia, and combined general and spinal anesthesia.