Epic Analysis of Sevoflurane and Isoflurane Usage Patterns and Fresh Gas Flow Rates

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Volatile anesthetic use is a significant source of medication cost in the operating theater. Cost is determined by dialed concentration and fresh gas flow (FGF) rate, with the latter having a greater impact on total use. In addition, volatile agents are recognized “greenhouse gases” and considered atmospheric pollutants. Sevoflurane has an FDA-mandated FGF requirement; however, if administered for less than one MAC hour, the rate can be decreased below the standard 2L/min. Isoflurane does not have a similar limit, and can therefore be run at a lower FGF rate than Sevoflurane. Higher FGF rates are typically used to accelerate titration of agent, especially at the start of a case. Return to normal FGF should be the goal within a relatively short time period. We designed this project to evaluate volatile use patterns in our operating rooms, with an eye towards reduction of cost and environmental impact.
As this was a departmental QI project and no patient identifiers were collected/viewed, IRB approval was waived. Volatile anesthetic choice and FGF rates were evaluated for all patients undergoing general anesthesia in the North Tower of Beaumont Hospital Royal Oak for one week – specifically FGF following induction of anesthesia (time before decreasing rates), average FGF during maintenance of anesthesia, and number of cases booked with (and presumed exposure). FGF and cost per bottle of agent were used for pharmaco-economic analysis, and data were expanded to project annual cost savings.
One week of cases were used for cost analysis. Cases performed under MAC or regional anesthesia were excluded from analysis. Isoflurane was the primary volatile agent in 25% of cases, with average FGF being 2.1L/min. Sevoflurane was the primary volatile agent in 75% of cases with average FGF being 2.6L/min. Time spent at high FGF following induction of anesthesia averaged 7.3min for Isoflurane and 4.7min with Sevoflurane. 95 cases were noted to have been boarded for
Although potential cost savings were modest, simple changes to practice patterns could have significant impact, especially if extrapolated to the greater healthcare system. Reducing FGF rate for Isoflurane below 1L/min, shortening time to dropping FGF after induction of anesthesia, and using 1L/min flow
rates of Sevoflurane for short procedures can reduce the cost of and the environmental exposure to volatile anesthetics.


American Society of Anesthesiologists, The Anesthesiology Annual Meeting, October 19-23, 2021, Orlando FL. Abstract Number: A3049