CARbon Impact of aNesthesic Gas - A Carbon Footprint Comparison of Sevoflurane and Desflurane in an Optimized Fresh Gas Flow Protocol

Assessing the impact of anesthesia practice on global warming and carbon footprint becomes part of the standard of care and is growing concern within the anesthesia community. Global Warming Potential (GWP) is a measure of how much a given mass of greenhouse gas contributes to global warming over a specified time period. Inhaled anesthetics have various GWP20: 349 for sevoflurane and 3714 for desflurane. However, GWP20 and CDE20 alone are not sufficient to evaluate the environmental impact of anesthetic gases. Other parameters must be included in the analysis: fresh gas flow (FGF), carrier gas (air, O2, N2O) and potency of the anesthetic gas. Unfortunately, the majority of trials did not fully consider the FGF reduction and the fact that desflurane can be administered with new closed or very low-flow anesthesia circuits as opposed as the recommended 2L/min that must be used for sevoflurane according to its monography in Canada. Most of the calculations were made on a purely theoretical approach that could be different from actual measurements based on a strictly monitored anesthesia practice. When continuous and accurate gas monitoring and analysis is used as recommended nowadays, the use of closed or semi-closed-circuit anesthesia with very low FGF might allow for a reduction of more than 80% of the anesthetic gas administration and its consequent pollution. By properly monitoring the anesthesia depth and analgesia adequacy, the investigators can reduce the gas consumption. The proposed study will aim at determining whether with the help of high-quality monitoring (BIS and NOL) and high-end ventilators that allow minimal fresh gas flow, the use of desflurane remains more polluting than sevoflurane.