In Response

Thank you very much for your attention to my article and your appreciation1 of its title: Desflurane Should Des-Appear: Global and Financial Rationale.2 Recently, a similar article supporting the elimination of desflurane was published with an equally punny title: Desflurane in Modern Anaesthetic Practice: Walking on Thin Ice(Caps)?3 Readership may enjoy that article as well. It does not surprise me that criticism of my article comes from an anesthesiologist who has received speaking fees from Baxter for desflurane promotion. I appreciate Dr Answine’s1 openness regarding this. Readers should consider the potential bias of his protective position toward desflurane. I acknowledge Dr Answine’s1 passion for desflurane. He believes desflurane is necessary for “high-risk patient populations undergoing high risk surgeries,”1 I do not, and I believe there are decades of data to support my position. Dr Answine’s1 letter claimed desflurane improves postoperative cognitive function. He cited a study from 2009 demonstrating quicker recovery of cognitive function with desflurane compared to sevoflurane.4 I cited a 2019 study that found a higher incidence of postoperative delirium in patients receiving desflurane compared to isoflurane.5 I also cited a meta-analysis from 2015 that found no difference in postoperative cognitive dysfunction between desflurane and sevoflurane.6 I reiterate my initial, peer-reviewed assessment: “While it is far from certain that desflurane is associated with worse postoperative cognition, it is equally uncertain that desflurane is associated with improved postoperative cognition.”2 Dr Answine1 commented that my article “did not discuss the impact to the environment of other anesthetics.” On the second page, the third paragraph under the subheading “Health Care and the Global Climate” reads “all volatile anesthetics are greenhouse gases…” Additionally, Figure 1 enumerates the relative carbon dioxide equivalents of the different volatile anesthetics at different fresh gas flows, and their associated social cost of carbon. Desflurane at 0.5 L of fresh gas flow per minute is multiples worse than sevoflurane or isoflurane at 2 L of fresh gas flows per minute.2 He proceeded to write “we cannot underemphasize the negative environmental effects of the intravenous anesthetics such as propofol.”1 However, Figure 2 of my article reads “Propofol has the smallest [greenhouse gas] impact per MAC-hour.”2 I cited a article documenting a cradle-to-grave, life-cycle assessment of propofol, desflurane, sevoflurane, and isoflurane. This article concludes: “[greenhouse gas] impacts of propofol are comparatively quite small, nearly 4 orders of magnitude lower than those of desflurane.” To be clear, this life cycle assessment included all the plastic tubing and syringes needed for the delivery of propofol.7 Coincidentally, Dr Answine1 cited this very same Sherman et al7 article when making his most interesting point, “Dr Meyer failed to mention the utilization of waste gas elimination devices now available to dramatically lower the release of desflurane into the environment.”1 However, immediately after the Sherman et al7 article mentions charcoal absorbers, it qualifies their utility by explaining the once-absorbed volatile agents leach into the atmosphere over a few days from the charcoal and thus charcoal absorbers “do not prevent emissions.” This concept of trapping anesthetic gases may be possible in the future—Baxter, the same corporation which is a large distributor of desflurane,8 is promoting a technology9 that claims to capture waste anesthetic gases in a special canister. More importantly, the scheme is for these filled canisters to be returned to factories that will recover the anesthetic gases, and then resell the anesthetic gases for use in anesthesia. It does not seem that this entire process is active yet, but theoretically, if safe and well-executed, it is a fantastic idea and demonstrates the circular economy. Health care waste harms human health,10 and to minimize this harm, the entire health care ecosystem needs to commit to the circular economy. Health care inventors need to consider the end of their products; simply entering the waste stream is no longer an acceptable option. Modern medical product design should mandate a cradle-to-grave, life-cycle analysis to ensure efficiency, and permit comparison between products. If Baxter can expand its application of the circular economy to its entire portfolio of health care products, it does not need to worry about desflurane sales, as it will be well positioned to capture the health care product market of the near future. There is no perfect anesthetic agent. With the right anesthesiologist, and the right attention to the patient, most anesthetic agents can be used for most surgical cases. As I acknowledged in the original article, “With health care’s emphasis on value-based care, considering what we know about desflurane’s financial and environmental costs, the onus is on the clinician to have evidence for improved outcomes for their patient when choosing desflurane.”2 Matthew J. Meyer, MDDepartment of AnesthesiologyUniversity of VirginiaCharlottesville, Virginia[email protected]