July 31, 2023 By Rachelle Armstrong Written by Seema Gandhi, MD. The University of California, San Francisco (UCSF) Health system is acting on its pledge to support climate health by leading the way nationally to removing central piped nitrous oxide (N2O) from its hospitals’ infrastructure. This bold landmark move will significantly decrease the facilities’ usage of N2O, an anesthetic agent and a potent greenhouse gas, reducing UCSF Health’s impact on the environment and moving one step closer toward healthcare decarbonization. N2O, also known as “nitrous” or “laughing gas,” was first introduced as an effective anesthetic gas in 1844 and has since been used worldwide due to its ease of use, affordability, and safety profile (1). It can be used as an independent anesthetic or as a carrier gas alongside oxygen, thereby decreasing the necessary concentration of other volatile anesthetic agents, such as isoflurane or sevoflurane, that are often used in combination. N2O gas is commonly delivered from large cylinders in the back of a healthcare facility to the anesthesia machines in operating rooms through a central pipe system concealed within the hospital’s walls (2). However, the pipe system is prone to leaks that are near-impossible to detect and can lead to a significant amount of gas unintentionally being vented into the atmosphere (3). One hospital recently found that up to 98% of its procured N2O was unaccounted for through clinical use, revealing that a substantial amount of the gas was being lost through leaks in pipes or faulty valves (4). In addition to being an unnecessary cost burden, the wasted N2O has severe environmental consequences, as the gas has a global warming potential 273 times that of carbon dioxide and an atmospheric lifetime of over 100 years. 5–7 N2O is currently the single greatest contributor to the destruction of the ozone layer, outranking even chlorofluorocarbons (CFCs), which are notorious for their ozone-depleting properties (8). Rising awareness of the environmental impact of N2O coupled with increased use of alternative anesthetics have decreased the demand for nitrous in the operating room. Despite the general trend of reduction in clinical use, UCSF’s facility procurement data continued to show an increase in N2O purchases. Through a quality improvement initiative led by Dr. Seema Gandhi, a UCSF anesthesiologist, and the Medical Director of Sustainability, and her team, the clinical usage data for nitrous in each operating room was collected through the electronic health record and compared with the procurement data. Based on the clinical usage data from the past five years, the average nitrous utilization rates varied between 4.5% to 35% at different operating suites. The significant discrepancy between clinical usage and procurement indicates a substantial amount of gas waste through the piping system. Following discussions with stakeholders across the Department of Anesthesia, facilities management, and safety personnel, an agreement was reached that piped N2O distribution is no longer required and an alternative cylinder-based system would not only maintain the same quality of clinical care but decrease health system Scope 1 emissions. In response to the current climate health crisis and the University of California’s ambitious carbon neutrality initiative, UCSF Health has eliminated the central piped N2O at the new outpatient surgical center at the Mission Bay campus and in the new hospital design plan at Parnassus Heights, as well as decommissioned the central nitrous pipe system from the majority of the existing surgical sites, including Parnassus Heights and its outpatient surgical center, Mount Zion, and the Orthopedic Institute. Smaller gas cylinders that are installed at the back of the anesthesia machine, known as E-cylinders, will be used in the operating rooms to supply N2O when needed. By taking these steps in modifying hospital infrastructure, UCSF Health will reduce the amount of N2O released from its facilities into the atmosphere by more than 80%. This decrease in Scope 1 emissions will equate to nearly 2.7 million fewer miles driven by a standard gasoline vehicle (9). Dr. Seema Gandhi has spearheaded the transition to e-cylinders for nitrous oxide at UCSF Health. Her previous works include reducing Greenhouse gas emissions released from the anesthesia practice by eliminating desflurane and adopting low fresh gas flow rates and reducing waste in the operating room. Through focus and support from the University of California Office of the President, she will continue to expand this effort to the other four UC health systems, host workshops to engage a wide range of stakeholders across UC Health and create an accessible toolkit to help other institutions to achieve emission reduction. As a leading academic health system that is committed to decarbonization, decommissioning piped nitrous in our new hospitals and across our current surgical sites will further decrease our emissions that are generated onsite while minimally impacting clinical practice. This critical infrastructure update is an active response to the urgent effort to decarbonize healthcare and reduce the impact of clinical practice on the environment. This further highlights UCSF and our commitment towards climate action and decarbonization. REFERENCES Buslov A, Carroll M, Desai MS. Frozen in time: A history of the synthesis of nitrous oxide and how the process remained unchanged for over 2 centuries. Anesth Analg. 2018;127(1):65-70. doi:10.1213/ANE.0000000000003423 Kibelbek MJ. Nitrous Oxide Supply Systems. Anesth Analg. 2018;127(5):E91. doi:10.1213/ANE.0000000000003767 Seglenieks R, Wong A, Pearson F, McGain F. Discrepancy between procurement and clinical use of nitrous oxide: waste not, want not. Br J Anaesth. 2022;128(1):e32-e34. doi:10.1016/j.bja.2021.10.021 Stein S. Hospitals Curbing Emissions Switch Anesthesia Gases , Plug Leaks. Bloomberg Law: Environment and Energy Report. https://news.bloomberglaw.com/environment-and-energy/hospitals-curbing-emissions-switch-anesthesia-gases-plug-leaks. Published 2022. Sherman J, Le C, Lamers V, Eckelman M. Life cycle greenhouse gas emissions of anesthetic drugs. Anesth Analg. 2012;114(5):1086-1090. doi:10.1213/ANE.0b013e31824f6940 Muret J, Fernandes TD, Gerlach H, et al. Environmental impacts of nitrous oxide: no laughing matter! Comment on Br J Anaesth 2019; 122: 587–604. Br J Anaesth. 2019;123(4):e481-e482. doi:10.1016/j.bja.2019.06.013 Prather MJ, Hsu J, Deluca NM, et al. Measuring and modeling the lifetime of nitrous oxide including its variability. J Geophys Res Atmos. 2015;120:5693-5705. doi:10.1002/2015JD023267.Received Ravishankara AR, Daniel JS, Portmann RW. Nitrous oxide (N2O): The dominant ozone-depleting substance emitted in the 21st century. 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