Climate change due to inhalation anaesthetics
Inhalation anaesthetics (volatile anaesthetics) are anaesthetic gases used to maintain general anaesthesia. Desflurane, sevoflurane, isoflurane, nitrous oxide (N2O) and the noble gas xenon are currently authorised in Germany. Chemically, all inhalation anaesthetics except N2O and xenon are halogenated hydrocarbons in which one or more hydrogen atoms have been replaced by fluorine and chlorine.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 therefore a chlorofluorocarbon (CFC).
Climate and ozone-depleting properties
CFC gases are ozone-depleting and, together with HFC gases, are highly potent greenhouse gases. In addition to its greenhouse gas effect, nitrous oxide also has an ozone-depleting effect. with an atmospheric lifetime of about 121 years.
Of all the volatile anaesthetics, desflurane has by far the most greatest climate-damaging effect. 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, an area in which natural greenhouse gases (CO2, Methanenitrous oxide) do not cause any reflection of the radiating infrared radiation. In 1987, a reduction of CFC gases in the Montreal Protocol agreed at 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 effect in Kigali. However, anaesthetic gases are not included in this treaty as they are medically necessary substances. Thus, anaesthetic gases are now the only HFC compounds whose concentrations are released into the atmosphere.
Measurable increase in the atmosphere worldwide
The Increasing use of desflurane worldwide and sevoflurane can be demonstrated by a visibly measurable increase in the atmosphere. Causes 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 anaesthetics used today*. In a hospital, currently approx. 25 per cent of greenhouse gas emissions from the use of inhaled anaesthetics.
Compared to sevoflurane, a significantly higher gas concentration is necessary for general anaesthesia with desflurane. Furthermore, it is necessary to specify the "global warming potency" on shorter time windows, since anaesthetic gases, except nitrous oxide, all have an atmospheric lifetime of less than 20 years. These effects should be considered as a CO2 footprint per anaesthetic procedure. For example, the CO2 footprint for the 1-year time window of a 7-hour general anaesthesia at a fresh gas flow of 2 l/min with
- Sevoflurane of a car journey of 3,132 km
- Desflurane of a car journey of 15,698 km
By reducing the fresh gas flow (low flow anaesthesia 0.5l/min) during anaesthesia, the CO2 footprint significantly reduced become. However, the better alternative would be to conduct a General anaesthesia via the vein with propofol or, if possible, the use of regional anaesthesia procedures. Both processes leave a significantly lower carbon footprint
© Priv. Doz. Susanne Koch, MD, Forum Sustainability in Anaesthesiology (DGAI/BDA) 10/2021
* Koch S, et al. Survey regarding routine use of anaesthetic procedures and related knowledge on environmental impact in Germany 2021. European Journal of Anaesthesiology.