Airway procedures: the importance of distinguishing between high risk and aerosol generation.

The NHS is the UK's biggest public sector employer and one of the greatest contributors to climate change The scale of annual carbon dioxide (CO2) emissions by the NHS is estimated at 27 million tonnes [1] Halogenated anaesthetic gases, such as isoflurane, sevoflurane, desflurane and nitrous oxide, contribute to 5% of all greenhouse gas emissions by acute NHS organisations [2] Methods A retrospective audit was carried out over a 2-week period in October 2019 at Salisbury District Hospital Data were collected from each of the Drager Primus machines From the collated data, we calculated the average flow rate (litres per minute), average agent consumption (millilitres per hour), average agent consumption per hour of anaesthesia and kilogram of CO2 equivalence per hour, per volatile agent Results The total consumption of anaesthetic gases was found to be 752 ml for sevoflurane, 268 ml for isoflurane, 490 ml for desflurane and 384 ml for nitrous oxide This generated an equivalent total CO2 of 147 4, 203 7, 1809 and 179 3 kg, respectively The average CO2 emission per hour was 24 8 kg with an average flow rate of 2 37 l min-1 The results were presented at the clinical governance meeting in June 2020 for which anaesthetists were encouraged to use low flows during general anaesthesia along with increased use of sevoflurane and reduced usage of isoflurane, desflurane and nitrous oxide Stickers were placed on all anaesthetic machines, indicating the CO2 equivalence per hour of each volatile agent along with the distance equivalent (in kilometres) in a motor vehicle An email was circulated with the audit results and recommendations A re-audit was undertaken over a 2-week period in June 2020, once elective surgery restarted after the peak of the COVID-19 pandemic Results have shown a reduction in average CO2 equivalence per hour of anaesthesia by 74% The usage of sevoflurane has almost doubled from 49% to 98% The use of nitrous oxide has fallen slightly from 34% to 28% The average flow rate has fallen from 2 37 to 1 9 l min-1 The data sets from both October and June capture about 100 h of operating time Discussion Our re-audit has shown that, with encouragement, we have made a massive impact in reducing our global warming impact by the increased use of sevoflurane and reduction in isoflurane, desflurane and nitrous oxide usage The re-audit highlights the further need for us to use low flows, particularly with sevoflurane, to further reduce our global warming impact