Environmental impact of anaesthetic gases at a tertiary hospital: A comparison of subspecialties and analysis of anaesthetic choices (2021)

Type of publication:
Conference abstract

Ito Y.; Takacs R.; Mittal R.; *Damm E.; Daley H.

Anaesthesia; Jul 2021; vol. 76 ; p. 103

The Anthropocene has already caused warming exceeding 1.2degreeC compared to pre-industrial levels, resulting in profound, immediate and rapidly worsening health effects. The climate crisis will continue to worsen without meaningful intervention [1]. Five per cent of the total carbon footprint (CF) of the NHS is due to inhalational anaesthesia [2]. Anaesthetists therefore have a unique opportunity and obligation to intervene [2]. Methods: Data of inhaled anaesthesia during maintenance phase were collected in 13 theatres in a tertiary hospital over a 9-day period. Data were extracted from Maquet Flow-i anaesthetic machines and the Bluerspier theatre information system. Case categories included emergency, elective and trauma; covering most surgical specialties. The 'Anaesthetic Impact Calculator' application was used to calculate the equivalent of CO2 kg.h-1 produced, cost, and km.h-1 for a car (efficiency 122 g.km-1). End tidal (ET) sevoflurane of 2.1, flow of 0.3 l.min-1, was used to calculate a benchmark of ideal volatile use. Results One hundred and seventy-three cases with complete datasets were included. Eighty-six per cent were performed under general anaesthesia (GA). Sixty-six per cent of cases used sevoflurane, 16% isoflurane, and 4% desflurane. Desflurane increased the cost and CF significantly, whereas N2O increased CF only. Fifty per cent of desflurane usage was in neurosurgery, followed by general and thoracic surgery. N2O was used in 20% of cases, of which 64% were trauma. Thirty per cent of paediatric cases used N2O, compared to 18% in adults. The highest CO2 kg.h-1 was recorded for emergency work (17.6), followed by elective (7.7), then trauma (4.7). Our data suggest this was mostly due to excessive gas flow. General surgery was first at (19.7), followed by neuro (16), and thirdly thoracic surgery (9.4). If using ET sevoflurane of 2.1 with 0.3 l.h-1 O2, a total of 2916 kg of CO2 could have been saved; equivalent to driving 24,065 km, or saving 1284. Discussion Sixty-six per cent of cases used sevoflurane, with few at low-flow rates. An alarming 20% used N2O. Only 14% of cases used techniques that avoided GA. There was a significant variation of CF between specialties. Our project is likely to under-represent the CF/anaesthetic as induction was not included. Every effort should be taken to use anaesthetic techniques avoiding use of inhalational anaesthesia. If required, lower carbon alternatives should be used at low flow, avoiding N2O. This is in line with the NHS Long Term Plan committed to lowering the 2% of the NHS' CF from anaesthetic gases by 40% [2].

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