Anaesthetics add to global warming

Inhaled anaesthetics used to put patients to sleep during surgery contribute to global climate change, according to a new study.

Researchers determined that the use of these anaesthetics by a busy hospital can contribute as much to climate change as the emissions from 100 to 1,200 cars a year, depending on the type of anaesthetic used, said University of California anaesthesiologist Dr Susan M. Ryan and fellow study author Claus J. Nielsen, a computer scientist at the University of Oslo in Norway.

The three major inhaled anaesthetics used for surgery - sevoflurane, isoflurane, and desflurane - are recognised greenhouse gases, but their contribution to climate change has received little attention because they're considered medically necessary and are used in relatively small amounts.

Gases remain in atmosphere

These anaesthetics undergo very little metabolic change in the body, the researchers noted. When they're exhaled by patients, they're almost exactly the same as they were when administered by anaesthetist. The anaesthetics "usually are vented out of the building as medical waste gases," the study authors wrote in a news release. "Most of the organic anaesthetic gases remain for a long time in the atmosphere where they have the potential to act as greenhouse gases."

Desflurane has a 10-year "lifetime" in the atmosphere, compared with 3.6 years for isoflurane and 1.2 years for sevoflurane. When they factored in the flow rates at which the different anaesthetics are given, the researchers calculated that desflurane has about 26 times the global warming potential as sevoflurane and 13 times the potential of isoflurane.

Using desflurane for one hour is equivalent to 235 to 470 miles of driving, according to the study.

The environmental impact of anaesthetics can be reduced by not using nitrous oxide unless there are medical reasons to do so, avoiding unnecessarily high anaesthetic flow rates (especially with desflurane) and by developing new methods of capturing anaesthetic gases for reuse, rather than releasing them into the atmosphere, the researchers suggested.

The study appears in the July issue of the journal Anaesthesia & Analgesia. - (HealthDay News, July 2010)