Anaesthesia for knee replacement surgery has considerable carbon footprint

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Anaesthesia for a single total knee replacement surgery has a carbon footprint equivalent to driving a car 67km, according to a study published in Anesthesiology, the official peer-reviewed journal of the American Society of Anesthesiologists.

A carbon footprint is the amount of carbon dioxide and other carbon compounds emitted due to the consumption of fossil fuels by a particular person, group or activity. Carbon dioxide (CO2) emissions are similar for general, spinal, and combined anaesthesia approaches according to the new research led by Dr Forbes McGain from Western Health in Melbourne. In addition to anaesthetic gasses, important contributors to the carbon footprint of surgical anaesthesia include the use of electricity, disposable items or equipment, and pharmaceutical products such as medications.

In the study, “Carbon Footprint of General, Regional, and Combined Anesthesia for Total Knee Replacements”, Dr. McGain and colleagues performed a life cycle assessment to estimate the CO2 emissions that resulted from knee replacement surgery. Life cycle assessments consider not only the greenhouse gasses directly produced by electricity and gas, but also the indirect emissions associated with the consumption of goods and services.

The study included 29 patients undergoing knee replacement surgery with general, spinal, or combination anaesthesia. General anaesthesia was mainly performed using the inhaled anaesthetic sevoflurane. Spinal and combination anaesthesia were alternative techniques used to improve recovery, while reducing pain and side effects. Dr. McGain and colleagues analysed total CO2 emissions, as well as specific sources of the emissions.

Overall estimated average CO2 emissions were similar, with significant overlaps, across the three groups: 14.9 kilograms (kg) CO2 for general anaesthesia, 16.9 kg for spinal anaesthesia, and 18.5 kg for combination anaesthesia. In all groups, major sources of CO2 emissions were:

  • Single-use (disposable) items, mainly plastics: 20% to 25% of total emissions
  • Electricity for the patient air warmer: about 15% of emissions
  • Pharmaceutical products (other than anaesthetics): 8% of emissions

Some sources varied by anaesthesia type. Sevoflurane accounted for 32% of total emissions in the general anaesthesia group and 17% in the combined group. Washing and sterilising reusable items contributed 25% of emissions with spinal anaesthesia and 20% with combined anaesthesia. Oxygen accounted for 15% of the carbon footprint of spinal anaesthesia.

Based on the fuel efficiency of the average U.S. car, carbon emissions from anaesthesia for one knee replacement surgery is equivalent to driving 67km, the researchers estimate. They note that the carbon footprint of anaesthesia likely varies between countries. For example, in Australia, where we still rely heavily on coal to produce electricity, indirect emissions are greater than in Europe or the U.S.

Dr. McGain and co-authors outline steps anaesthesiologists can consider to safely provide anaesthesia while reducing their carbon footprint: lowering oxygen flow rates for spinal anaesthesia, reducing inhaled anaesthetic use, minimising plastic and glass use, and advocating for renewable energy production. "When combining these carbon-sparing activities, you've halved the miles driven for the 3-hour anaesthetic (typically required for knee replacement surgery)," the researchers wrote.

The researchers concluded, "We encourage cognisance of one's carbon footprint, emphasising that instigating multiple, seemingly small changes in our workplace patterns is the best path to low carbon anaesthesia."