Reducing Greenhouse Gas Emissions and Modifying Nitrous Oxide Delivery at Stanford: Observational, Pilot Intervention Study.

BACKGROUND

Inhalational anesthetic agents are a major source of potent greenhouse gases in the medical sector, and reducing their emissions is a readily addressable goal. Nitrous oxide (NO) has a long environmental half-life relative to carbon dioxide combined with a low clinical potency, leading to relatively large amounts of NO being stored in cryogenic tanks and H cylinders for use, increasing the chance of pollution through leaks. Building on previous findings, Stanford Health Care's (SHC's) NO emissions were analyzed at 2 campuses and targeted for waste reduction as a precursor to system-wide reductions.

OBJECTIVE

We aimed to determine the extent of NO pollution at SHC and subsequently whether using E-cylinders for NO storage and delivery at the point of care in SHC's ambulatory surgery centers could reduce system-wide emissions.

METHODS

In phase 1, total SHC (Palo Alto, California) NO purchase data for calendar year 2022 were collected and compared (volume and cost) to total Palo Alto clinical delivery data using Epic electronic health records. In phase 2, a pilot study was conducted in the 8 operating rooms of SHC campus A (Redwood City). The central NO pipelines were disconnected, and E-cylinders were used in each operating room. E-cylinders were weighed before and after use on a weekly basis for comparison to Epic NO delivery data over a 5-week period. In phase 3, after successful implementation, the same methodology was applied to campus B, one of 3 facilities in Palo Alto.

RESULTS

In phase 1, total NO purchased in 2022 was 8,217,449 L (33,201.8 lbs) at a total cost of US $63,298. Of this, only 780,882.2 L (9.5%) of NO was delivered to patients, with 7,436,566.8 L (90.5%) or US $57,285 worth lost or wasted. In phase 2, the total mass of NO use from E-cylinders was 7.4 lbs (1 lb NO=247.5 L) or 1831.5 L at campus A. Epic data showed that the total NO volume delivered was 1839.3 L (7.4 lbs). In phase 3, the total mass of NO use from E-cylinders was 10.4 lbs or 2574 L at campus B (confirming reliability within error propagation margins). Epic data showed that the total NO volume delivered was 2840.3 L (11.5 lbs). Over phases 2 and 3, total use for campuses A and B was less than the volume of 3 E-cylinders (1 E-cylinder=1590 L).

CONCLUSIONS

Converting NO delivery from centralized storage to point-of-care E-cylinders dramatically reduced waste and expense with no detriment to patient care. Our results provide strong evidence for analyzing NO storage in health care systems that rely on centralized storage, and consideration of E-cylinder implementation to reduce emissions. The reduction in NO waste will help meet SHC's goal of reducing scope 1 and 2 emissions by 50% before 2030.