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Climate change due to inhalation anesthetics

Inhalation anesthetics (volatile anesthetics) are anesthetic gases used to maintain general anesthesia. Desflurane, sevoflurane, isoflurane, nitrous oxide (N2O) and the noble gas xenon are currently permitted in Germany. Chemically, all inhalation anesthetics except N2O and xenon are halogenated hydrocarbons in which one or more hydrogen atoms have been replaced by fluorine and chlorine. Sevoflurane and desflurane are pure fluorocarbons (HFCs). Isoflurane contains an additional chlorine atom and is thus a chlorofluorocarbon (CFC).

 

 

Climate and ozone depleting characteristics

CFC gases are ozone-depleting and, with HFC gases, are highly potent greenhouse gases. In addition to its greenhouse gas effect, nitrous oxide also exhibits an ozone-depleting effect with an atmospheric lifetime of approximately 121 years.

Desflurane has by far the greatest climate-damaging effect of all volatile anesthetics. Thus, over the time window of 100 years, desflurane shows a 1,620 higher "global warming potency (GFW)" compared to the reference greenhouse gas CO2.

The strong global warming potential of HFC and CFC compounds is caused by the high absorption and reflection of infrared radiation in the so-called atmospheric window, a region in which natural greenhouse gases (CO2, methane, nitrous oxide) do not cause reflection of radiating infrared radiation. In 1987, a reduction of CFC gases was agreed upon in the Montreal Protocol of the Conference of the Parties to the United Nations Framework Convention on Climate Change to protect the ozone layer. This was expanded in 2016 to include HFC compounds due to their high climate-damaging effects in Kigali. However, anesthetic gases are not included in this treaty because they are medically necessary substances. Thus, anesthetic gases are nowadays the only HFC compounds whose concentrations are released into the atmosphere.

Measurable increase in the atmosphere worldwide

The increasing use of desfluran and sevoflurane worldwide can be demonstrated by a measurable increase in the atmosphere. The reasons for this are the increasing world population, improved medical care and the increasing age of people combined with more frequent operations. In Germany, sevoflurane and desflurane are the primary inhaled anesthetics used today*. The use of inhaled anesthetics currently accounts for approximately 25 percent of greenhouse gas emissions in a hospital.

Compared to sevoflurane, a significantly higher gas concentration is required for general anesthesia with desflurane. Furthermore, it is necessary to report the "global warming potency" on shorter time windows, since anesthetic gases, except nitrous oxide, all have an atmospheric lifetime of less than 20 years. These effects should be accounted for as a CO2 footprint per anesthetic procedure. For example, the CO2 footprint for the 1-year time window corresponds to 7 hours of general anesthesia at a fresh gas flow of 2 l/min with

  • sevoflurane a car trip of 3,132 km

  • desflurane a car trip of 15,698 km

By reducing the fresh gas flow (low-flow anesthesia 0.5l/min) during anesthesia, the CO2 footprint can be significantly reduce . However, the better alternative would be to perform general anesthesia via vein with propofol or, if possible, to use regional anesthesia procedures. Both procedures leave a significantly lower CO2 footprint.

* Koch S, et al. Survey regarding routine use of anaesthetic procedures and related knowledge on environmental impact in Germany 2021. European Journal of Anaesthesiology.

© Priv. Doz. Dr. med. Susanne Koch, Forum Nachhaltigkeit in der Anästhesiologie (DGAI/BDA) 10/2021

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