Environmental And Economic Impact of Using A Higher Efficiency Ventilator And Vaporizer During Surgery Under General Anesthesia: A Randomized Controlled Prospective Cohort

Abstract

Background: Compared to traditional breathing circuits, low-flow anesthesia machines utilize a low-volume breathing circuit system by injecting volatile agent into the circuit mainly during inspiration. We aimed to assess whether Maquet Flow-i C20 anesthesia workstation delivers volatile anesthetic more efficiently than a GE Aisys CS2 during elective general surgery. Methods: Eligible candidates enrolled in the study (2014-1248) met the following inclusion criteria: 18 – 65 years old, scheduled for surgery requiring general anesthesia at UC Irvine Health, and expected to receive sevoflurane for the duration of the procedure. Exclusion criteria: < 18 years old, history of COPD, cardiovascular disease, sevoflurane sensitivity, BMI > 30 kg/m2, ASA > 2, pregnant, or surgery scheduled < 120 minutes. We calculated the total amount of sevoflurane delivered and consumption rates during induction/maintenance periods and compared the groups using parametric testing (Student’s t-Test). Results: In total, 103 subjects (Maquet: n=52, GE: n=51) were analyzed. Overall, the Flow-i C-20 group consumed significantly less sevoflurane (95.5 ± 49.3 g) compared to the Aisys2 (118.2 ± 62.4 g) (p = 0.043 for group difference) corresponding to an approximately 20% efficiency improvement in overall agent delivery. When accounting for the fresh gas flow setting, agent concentration and length of induction, the Maquet machines delivered volatile agent at a significantly lower rate compared to the GE devices (7.4 ± 3.2 L/min vs. 9.2 ± 4.1 L/min; p = 0.017). Based on these results, we estimate that the Maquet Flow-i workstations can save an estimated average of $239,440 over the expected 10-year machine lifespan. This 20% decrease in CO2 equivalent emissions corresponds to 201 metric tons less greenhouse gas emissions over a decade compared to the GE Aisys; equivalent to 491,760 miles driven by an average passenger vehicle or 219,881 pounds of coal burned.Conclusions: Overall, our results from this pilot study suggest that the Maquet Flow-i delivers significantly less (~20%) volatile agent during routine elective surgery using a standardized anesthetic protocol compared to a traditional anesthesia system. The results demonstrate a strong opportunity for economic and environmental benefits if implemented across other medical institutions.