Carbon dioxide equivalency (CO2e) describes the amount of carbon dioxide (CO2) that would have the same Global warming potential (GWP) as the gas in question. GWP100 represents the ability of a gas to warm the earth’s atmosphere over a 100 year period, relative to one mass unit of carbon dioxide.
All inhalation anaesthetic agents are potent green house gases, with Desflurane being particularly harmful (See Table 1). It is believed that volatile anaesthetic gases account for 5% of the CO2e from acute trusts (Sustainable Development Unit). The NHS long term plan has planned for a 51% reduction in the NHS carbon footprint by 2025, with 2% of this to come through “transforming anaesthetic practices”.
Table 1 - Physical properties of commonly used IAA’s [1 - 5]
The following references were used in the calculations found above:
Andersen, M. P. S., Nielsen, O. J., Wallington, T. J., Karpichev, B., & Sander, S. P. (2012). Assessing the impact on global climate from general anesthetic gases. Anesthesia & Analgesia, 114(5), 1081-1085.
Sulbaek Andersen, M. P., Nielsen, O. J., Karpichev, B., Wallington, T. J., & Sander, S. P. (2011). Atmospheric chemistry of isoflurane, desflurane, and sevoflurane: kinetics and mechanisms of reactions with chlorine atoms and OH radicals and global warming potentials. The Journal of Physical Chemistry A, 116(24), 5806-582
Nickalls, R. W. D., & Mapleson, W. W. (2003). Age‐related iso‐MAC charts for isoflurane, sevoflurane and desflurane in man. British journal of anaesthesia, 91(2), 170-174.
Campbell, M., & Pierce, J. T. (2014). Atmospheric science, anaesthesia, and the environment. Bja Education, 15(4), 173-179.
Pierce T. Real time calculator available for download at https://anaesthetists.org/Home/Resources-publications/Environment/Guide-to-green-anaesthesia/Anaesthetic-gases-calculator.
The Desflurane Dashboard
Desflurane use and associated CO2e reductions across the Network
Each centre has used varying yet equally engaging change management strategies, in all cases achieving significant reductions in CO2e production relating to Desflurane and significant financial savings. University Hospitals Bristol and Gloucestershire Hospitals have been awarded the following accolades for their work.
RODAC at University Hospitals Bristol NHS Foundation Trust (UHB)
Strategy for Change
Volatile usage at UHB was analysed using the Define database. A metric of environmental impact was generated through multiplication of the number of bottles vapourised by the CO2e per bottle (886kg for Desflurane). Using the Environmental Protection Agency’s (EPA) green house gas equivalence calculator, we quantified this into tangible every day equivalencies, such as coal burnt or miles driven. Over a two month period, prompt cards containing facts regarding volatiles and the environment were placed on top of all anaesthetic machines in UHB (See Figure 1).
A quick response code on these cards directed clinicians to the project website, a basic site which compiled a number of relevant educational resources. In addition we utilised an interactive anagram on every card, which when solved revealed ‘Consider the environmental and financial impact of volatile anaesthetics on future generations‘, this process was explained on the website and prizes awarded to the successful few.
Calculations based on the 7 months pre and post implementation of RODAC
119610 kg - The total reduction in CO2e.
17,087 kg - The average monthly reduction in CO2e.
41,778 miles - The number of miles driven by a standard passenger car to produce the equivalent CO2e per month (Greenhouse Gas Equivalancie’s Calculator).
£10,843 - Total financial savings due to reduced Desflurane use.