To the Editor:
The article “Carbon Footprint of General, Regional, and Combined Anesthesia for Total Knee Replacement” by McGain et al. provides welcome dialogue in the evidence-sparse domain of carbon equivalent comparisons between anesthetic modalities. Their paper describes prospective life cycle assessment of anesthetic components of total knee joint replacement surgery, and found similar carbon dioxide equivalent emissions for spinal anesthesia, general anesthesia, and combined spinal with general anesthesia (14.9 to 18.5 kg CO2 equivalents per case). While it may be tempting to interpret these findings as representing environmental equipoise, there are several institutional and geographical differences that we think are relevant to consider when implementing this research locally, and to encourage thoughtful advocacy in the important task of healthcare climate work.
Western Health, the Melbourne, Australia, hospital in which this study was conducted uses a laudable range of reusable anesthetic items, including facemasks, Proseal (Teleflex Medical Europe Ltd, Ireland) laryngeal masks, laryngoscope blades, anesthesia circuits, spinal trays, drug trays, sterile gowns, cotton drapes, and cotton hand towels. Despite this, single-use products still comprised approximately 20 to 25% of all emissions for the three anesthetic modalities examined. We propose that in most institutions that have not implemented reusable equipment like Western Health, the carbon emissions for all anesthesia options for a total knee replacement would be greater. Reusable equipment has a lower carbon footprint when renewable energy provides some or all of the energy, and is consistently cheaper such that hospitals that use single-use items in place of reusable items for a total knee replacement may have higher financial and environmental costs. Thus, institutional procurement will significantly affect anesthetic carbon dioxide equivalent calculations. For example, the carbon dioxide equivalent emission for using a reusable drug tray is 0.11 kg, compared to up to 0.20 kg for a single-use item. A reusable steel laryngoscope blade, including sterilization, produces 0.22 kg CO2 equivalents, compared to 0.44 kg for a single-use steel blade and a reusable laryngeal mask produces 7.4 kg CO2 equivalents, which corresponds to 40 disposable laryngeal masks, contributing 11.3 kg CO2 equivalents.4 This is not accounting for other reusable items, such as anesthetic circuits, sterile gowns, cotton drapes, and facemasks.
McGain et al. note that geographical variation in electricity energy sourcing alters the carbon dioxide–associated equivalent emissions per kilowatt-hour; however, these differences may be greater where hospitals currently use single-use items and transition to reusable equipment in locations with a high or increasing renewable energy mix. In the study by McGain et al., washing and sterilizing items contributed approximately 29% to the total carbon dioxide equivalent emissions for spinal anesthesia, and 20% for combined spinal and general anesthesia. As noted by the authors, healthcare electricity in Victoria, Australia, is currently coal-driven, but will be 100% renewable energy from 2025. As such, a renewable energy mix similar to the United Kingdom and Europe would translate to a fourfold reduction in carbon dioxide equivalent emissions for cleaned reusables. These considerations should compel clinicians to advocate for adopting reusable equipment and to continue to ensure governments make steady gains toward an increasingly renewable energy mix for healthcare electricity.
The research by McGain et al. invites us to consider how our relevant local hospital practices (product procurement and energy sourcing) impact our in-theatre carbon footprints, and to champion change to benefit our patients and our planet.