Greening the OR

• Use TIVA/regional techniques when possible. In cases where no volatile anesthetic is used, an in vitro study published in BJA in 2020 showed that FGF should be 6 LPM or match the patients MV (whichever is higher), to prevent undue consumption of CO2 absorbent. However, a follow up letter to the editor in 2022 by the same authors reporting their in vivo results was more nuanced. While CO2 absorber lifespan was indeed significantly prolonged in high flow TIVA patients (160 hrs vs 16 hrs), and running costs were significantly decreased, the GWP100 was moderately higher with FiO2 of 30%, and significantly higher if FiO2 was 60%. They speculate that selective use of high flows in high CO2 output TIVA cases (e.g. laparoscopic or bariatric) may yield environmental as well as economic benefits. A 2024 paper claimed that matching FGF to MV was always the more environmentally friendly option. Some of their assumptions were based on the above papers. My own analysis with some modifications to account for OHSU's cleaner grid intensity and different waste stream for CO2 absorbers (landfill vs. incineration) showed that there are select cases where low flow anesthesia during TIVA is still better. Specifically, if MV and FIO2 are both high, then the emissions cost of generating the air/O2 outweighs the CO2 absorber savings.