LAUSR

Recently, there has been a major drive to reduce the environmental impact of anaesthesia, in which the Association of Anaesthetists has been playing a leading role. A cornerstone of this effort is reducing the use of inhalational anaesthetic agents, all of which have harmful global warming effects, with desflurane being the worst offender. Desflurane produces 2540 times the global warming potential over 100 years (GWP100) compared with a mass equivalent of carbon dioxide [1] and is 50–60 times more harmful than sevoflurane MAC for MAC [2], depending onwhat values are used forMAC. Inspired by the Association, there have been many recent projects that have successfully reduced the amount of desflurane used by hospitals in several regions across the UK, some of which featured at the recent Trainee Conference in Telford [3–5]. A key concept in such work is that of carbon dioxide equivalents (CO2e); the mass of carbon dioxide that has the same GWP as a given mass of agent in question. For example, since desflurane has a GWP100 of 2540, 1 kg of desflurane produces an equivalent of 2540 kg of carbon dioxide. The CO2e a hospital generates from any given inhalational agent can then simply be calculated by multiplying the number of bottles of that inhalational agent a trust uses by the CO2e generated by vaporising an entire bottle of said inhalational agent. The CO2e of a bottle of desflurane is stated on the Association website as 886 kg (https://anaesthetists.org/Home/Re sources-publications/Environment), a figure originally published by Campbell and Pierce in their excellent educational article [6]. However, it appears that this figure is incorrect andneeds tobe updated. The CO2e of a bottle of inhalational agent is calculated using the following formula: