We read with interest the article by Mc Gain et al. presenting the comparative carbon footprint of two general and regional anesthesia techniques. As the authors point out, the results cannot be systematically extrapolated to other countries because of the different energy sources used in each country. An important point is the use in this study of reusable breathing circuits changed once a week, as is the case in several countries which considerably reduces costs and greenhouse gas emissions compared to North American practices that require changing circuits (mostly single-use) between each patient even when a filter is used.  It is conceivable that this would have had an impact on the results of the same study conducted in North America.

However, several recent studies have demonstrated, in vivo, that bacterial or viral contamination of an anesthesia circuit was very low and did not increase with the time of use when effective hydrophobic heat and moisture exchange filters were used, with a rigorous technique of filter change and cleaning of the anesthesia station.  In an effort to reduce operating room waste, which represents 25% of hospital waste,  it may be time to revise our recommendations to allow for safe and sustainable practice.