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The environmental impact of anesthetic gases

The potential health impacts of climate change are far reaching. Cardiovascular disease, heat-related asthma and malnutrition due to compromised food security are just a few of the associated risks. The health-care system in which patients are eventually treated is responsible for 8 percent of the nation’s greenhouse gas emissions. According to civil and environmental engineering assistant professor Matthew Eckelman, this all raises the interesting question of how the health-care industry itself is affecting our health through direct and indirect changes in our environment.

Eckelman looks at the life cycle of various products and processes — from production to destruction — to determine their overall environmental impact on a systems level. In a recent paper in a special issue of the journal Anesthesia & Analgesia, Eckelman and colleagues at Yale University performed life-cycle assessments of the major anesthetic gases used in the health-care industry: nitrous oxide (laughing gas), desflurane, isoflurane and sevoflurane, as well as a liquid anesthetic alternative, propofol.

“Any life-cycle assessment, Eckelman said, is a series of tradeoffs. The health-care system is designed to reduce human mortality and morbidity, but it is also important to understand the indirect or unintended effects that health care has on the environment and public health. “The health-care sector is increasingly concerned with sustainability issues,” he said.

Life cycle green­house gas (GHG) emis­sions of anes­thetics, including waste anes­thetic gas emis­sions of halo­genated drugs and nitrous oxide (N2O).

During a talk at the International Symposium on Sustainable Systems and Technology in Boston last week, Eckelman delivered the paper’s results, showing the relative environmental profile of each anesthetic alternative, and the important conclusion that the combined environmental impact of production, transportation, waste disposal and other life-cycle events pales in comparison to the impact of the anesthetic gases alone.[media-credit id=9 align=”alignright” width=”590″]

“Anesthetic gases like nitrous oxide and the three halogenated ethers are greenhouse gases themselves,” said Eckelman, who chaired a portion of the symposium, “and they’re quite potent.” Desflurane, for example, has a global warming potential more than 2,500 times that of carbon dioxide, he said.

Only small amounts of the gases are actually metabolized by the body. “The rest are usually vented out of the top of the hospital.” In addition to the anesthetic itself, these agents require a carrier gas, which can be oxygen combined with either air or nitrous oxide, said Eckelman. In cases where nitrous oxide is used, a large portion of the impact comes from emissions of the carrier gases.

Based on the research results, which put desflurane at the top of the list in terms of life-cycle greenhouse gas emissions, Eckelman and his team made a series of recommendations for both doctors and hospitals. Within medical and cost considerations, they suggest doctors should avoid desflurane where possible; use oxygen as a carrier gas instead of nitrous oxide; minimize fresh gas flow rates; and employ IV anesthetic alternatives in applicable cases — propofol’s environmental impacts are negligible compared to the inhaled anesthetics.

The paper, which links health and sustainability, two of the university’s central research themes, is part of a general international effort to bring life-cycle assessment to bear on various aspects of health-care practice. Civil and environmental engineering professor Matthew Eckelman delivered the results of an anesthetic-drug life-cycle assessment to the International Symposium on Sustainable Systems and Technology last week.