Impact of maintenance anaesthetics on total emissions of an atrial fibrillation catheter ablation procedure

© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (https://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com We read with interest the study ‘Carbon footprint of atrial fibrillation catheter ablation’. We appreciate the meticulous methodology and the practical road map to decrease the carbon footprint. We wish to emphasize that anaesthesia choices can significantly overshadow the overall procedure’s impact. A mean emission of 76.9 kg CO2 equivalents (CO2e) per procedure was concluded. Depending on the anaesthetist’s choice, maintenance anaesthesia can either have minimal impact, as seen with total intravenous anaesthesia producing less than 1 kg CO2e per hour, or dwarf any emissions from the procedure, as observed when using sevoflurane at a 6 L fresh gas flow, resulting in 183 kg CO2e per hour, or desflurane at a 6 L fresh gas flow, resulting in 1171 kg CO2e per hour. 4 The use of nitrous oxide, which can be easily omitted, can by itself add 180 kg CO2e per hour. Traditionally, a 20-year or 100-year time horizon is frequently employed, denoted as GWP20 and GWP100. When emissions arising from an activity consist primarily of CO2, the choice of time horizon has a negligible impact on the calculated CO2e. For international accounting, a conventional practice is to employ a 100-year time horizon. Nonetheless, for extremely potent greenhouse gases with a short atmospheric lifetime, such as volatile anaesthetics, this significantly underestimates the effects within the next decades and assumes the absence of any amplifying feedback mechanisms. Given the urgency of the climate crisis and the numerous positive feedback mechanisms that intensify the effects of initial emissions, a 20-year time horizon more accurately reflects the true climate impact. The detailed roadmap to decrease the carbon footprint shows that recycling of packaging (3.1 kg CO2e), recycling of precious metals (3.4 kg CO2e), suppressing instruction leaflets (0.8 kg CO2e), recycling of the majority of devices (7.8 kg CO2e), redesigning medical devices using an ecodesign approach (2.8 kg CO2e) and optimal reuse (5.8 kg CO2e) could lead to a total diminution of 23.7 kg CO2e per procedure, while 19.7 kg (26%) CO2e emissions were attributed to anaesthesia workstation and drugs. The specific anaesthetics used were not reported, and we presume that a 100-year time horizon was considered. Including production emissions associated with volatile anaesthetics, the use of 1 mL (=1.52 g) of sevoflurane corresponds to 2.1 kg CO2e for a 20-year time horizon and 0.6 kg CO2e for a 100-year time horizon. 4,6 For 1 mL (=1.46 g) of desflurane, the corresponding emissions are 11.3 kg CO2e for a 20-year time horizon and 4.2 kg CO2e for a 100-year time horizon. Table 1 displays volatile anaesthetics consumption and associated CO2e emissions during a 2-h procedure, varying with anaesthetic choice and nitrous oxide presence. These different scenarios still represent common practices in Europe. Total intravenous anaesthesia with propofol typically generates approximately 1 kg CO2e for 2 h of anaesthesia, encompassing all necessary consumables. Depending on the anaesthetist’s decisions, the CO2e emissions from 2-h maintenance anaesthesia can therefore range from 1 kg CO2e to 2.3 tons CO2e. Even the easily avoidable addition of nitrous oxide (N2O) can add more CO2e than the reported total emission from the procedure. The substantial environmental impact posed by specific maintenance anaesthetics underscores its importance in determining priority actions to decrease pollution from interventional procedures.