Anesthetic gases have a high global warming potential (GWP), and when not metabolized by the patient, end up being vented to the atmosphere by the medical vacuum or waste anesthesia gas disposal system.
Studies indicate that the majority of nitrous oxide use is wasted from piped, manifolded systems. In one study, up to 95% of purchased nitrous oxide was wasted. Nitrous oxide is included in the Kyoto Protocol*; other anesthesia gases are not specifically included but do contribute to GWP1.
How to measure and report:
Because anesthetic gases are basically unmetabolized, their use can be tracked by procured anesthetic drugs through the pharmacy department for desflurane, sevoflurane and isoflurane or the medical gas department for nitrous oxide.
Anesthetic gases use can be converted to carbon dioxide equivalent (CO2e) using the following conversion rates:
How to manage:
The best way to reduce GHG emissions due to anesthetic gases is to eliminate the use of central nitrous oxide systems. Some studies suggest that the majority of nitrous oxide use is due to leaks in the system, so decommissioning existing nitrous oxide system or avoiding a central system altogether and using portable E cylinders greatly reduces the GHG emissions.
Another good way to reduce GHG emissions is to use anesthetics with lower global warming potential, specifically by removing desflurane from use and using sevoflurane instead. Desflurane has a Carbon Dioxide Equivalent of 27 times that of sevoflurane and a Global Warming Potential of almost 11 times that of sevoflurane.
A final method to reduce GHG emissions is to minimize fresh gas flow rates. Typically, a greater volume of carrier gas flow (and therefore the amount of anesthetic gas) is delivered to the patient than needed. Tracking the volume of carrier gas flow via electronic anesthesia records will provide data to assist in working with the anesthesia team to reduce use.
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