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In Response

Sherman, Jodi, MD

doi: 10.1213/ANE.0b013e318280dff4
Letters to the Editor
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Department of AnesthesiaYale School of Medicine/Yale-New Haven HospitalNew Haven, Connecticutjodi.sherman@yale.edu

Drs. Mychaskiw and Eger1 express concern that the desire to accept responsibility for environmental stewardship may induce practitioners to modify inhaled anesthetic practices inappropriately. While I agree that not all anesthetic considerations are equal, there is opportunity for reducing our environmental impact while maintaining high standards of care.

Greenhouse gas (GHG) emissions associated with inhaled agents may be larger than previously suggested. The estimate cited by Sulbaek Andersen et al.2 for the total worldwide contribution of inhaled anesthetics to global warming—0.01%—is problematic. The authors based their extrapolation on only 1 US institution that uses comparatively little desflurane (the volatile agent contributing the greatest GHG pollution), and admittedly failed to account for nitrous oxide (N2O)—effectively underestimating contributions.a Furthermore, the 0.01% estimate ignores all dental, veterinary, and laboratory medicine use, as well as other life cycle phases such as manufacturing and transportation.b The true contribution of inhaled anesthetics is likely much higher, and reduction could easily be accomplished using strategies discussed in a recent editorial.c,3

Mychaskiw and Eger1 also note cost as important in decision-making in health care, and I agree. Interestingly, many environmental improvements to the practice of health care are financially advantageous, such as reprocessing medical devices, recycling, and minimizing hazardous waste.d Feldman demonstrated how routinely minimizing fresh gas flows could compound significantly over a career to avoid waste.4 Sulbaek Andersen et al.5 state “(e)xercising care to avoid excessive use of anesthetic gases has the double benefit of reducing health care costs and protecting the environment.” Does a particular anesthetic reduce cost as well?

While Eger and Shafer showed that desflurane could result in faster wake up times compared with that of other volatile agents in surgeries of short duration (<90 minutes), for longer surgeries, desflurane wake up times (time to 85% mean alveolar concentration decrement in vessel rich groups) are comparable with those of the other volatile agents.6 However, in this study, the volatile agent concentration was maintained at 1 MAC until the end of surgery instead of tapering it down as we do in actual practice, and therefore the difference between anesthetics was likely exaggerated. Whether shorter wake up times after shorter surgeries offset the higher cost of desflurane depends on many factors including: patient payor mix, efficiency of room turnover, staff reimbursement system, and availability of patients to fill potential operating room times.e

A culture shift has begun in medicine (Healthier Hospitals Initiative, f CleanMedg national scientific meetings, Choose Wiselyh national campaign to reduce unnecessary laboratory testing). We as a specialty pride ourselves on flexibility and balance of multiple factors, including patient safety. Long-term public health impacts are also part of a more efficient health care practice. The specialty of anesthesia should open its collective mind to exploring a safe practice within a new, more sustainable paradigm.

Jodi Sherman, MD

Department of Anesthesia

Yale School of Medicine/Yale-New Haven Hospital

New Haven, Connecticut

jodi.sherman@yale.edu

a The Sulbaek Anderson worldwide estimate was based solely on the University of Michigan’s practice in 2009, which used very little desflurane (6 L for 46,000 cases) and averaged 17 kg carbon dioxide equivalents (CO2 eq) per case (2012 global warming potentials over 100 years, GWP100). By comparison, purchasing data from the University of California, San Francisco in 2008 to 2009 indicate that that institution used much more desflurane, with associated GHG emissions of 98 kg CO2 eq per case. This difference is partially explained by the very high global warming potential of desflurane. Both institutions also make extensive use of nitrous oxide, and its inclusion would increase GHG emissions estimates further. For example, Yale-New Haven Hospital averaged 74 kg CO2 eq per case in 2010 if neglecting to account for N2O, and 165 kg CO2 eq with N2O.
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b No national case numbers are tracked for these surgical professions. Manufacturing and administration of inhaled anesthetics account for approximately 5% of total life cycle GHG contributions.
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c Since all of the inhaled anesthetics are potent GHGs while liquid anesthetics such as propofol are not, techniques such as Total IV Anesthesia and regional anesthesia will reduce climate impacts. When using inhaled drugs, simply avoiding desflurane and N2O wherever possible will reduce impacts since their GHG effects are 15 to 20 times higher than either isoflurane or sevoflurane. Earnest application of low flow anesthesia could save tens of thousands of liters of inhaled anesthetics over the course of a single provider’s career.
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d The Business Case for Greening the OR. Available at: http://practicegreenhealth.org/sites/default/files/upload-files/caseforgor_r5_web.pdf. Accessed September 7, 2012.
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e For example, the University of Utah Hospital delivers 25,000 anesthetics per annum and elected to cut desflurane usage in half. In 1 year, they subsequently reduced their inhaled anesthetic acquisition costs by $308,000 and saved the waste anesthetic GHG equivalent of 5.4 million miles driven, without increasing their turnover times. Propofol usage did not increase during this time period, while isoflurane use increased and sevoflurane use stayed the same. Personal communication with Dr. Harriet Hopf, MD, Professor of Anesthesiology, University of Utah, harriet.hopf@hsc.utah.edu.
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f It is an invitation for health care organizations across the country to join the shift to a more sustainable business model, and a challenge for them to address the health and environmental impacts of their industry. Available at http://healthierhospitals.org.
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g CleanMed is the annual meeting of Practice Greenhealth. See www.cleanmed.org.
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h Choose Wisely is an initiative by the American Board of Internal Medicine Foundation, representing all 9 subspecialties. See http://www.abimfoundation.org/Initiatives/Choosing-Wisely.aspx.
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REFERENCES

1. Mychaskiw G, Eger E. A different perspective on anesthetics and climate change. Anesth Anal. 2013;116:734–5
2. Sulbaek Andersen MP, Sander SP, Nielsen OJ, Wagner DS, Sanford TJ Jr, Wallington TJ. Inhalation anaesthetics and climate change. Br J Anaesth. 2010;105:760–6
3. Ryan S, Sherman J. Sustainable anesthesia. Anesth Analg. 2012;114:921–3
4. Feldman JM. Managing fresh gas flow to reduce environmental contamination. Anesth Analg. 2012;114:1093–101
5. Sulbaek Andersen MP, Nielsen OJ, Wallington TJ, Karpichev B, Sander SP. Medical intelligence article: assessing the impact on global climate from general anesthetic gases. Anesth Analg. 2012;114:1081–5
6. Eger EI 2nd, Shafer SL. Tutorial: context-sensitive decrement times for inhaled anesthetics. Anesth Analg. 2005;101:688–96 table of contents
© 2013 International Anesthesia Research Society