Saving sevoflurane: Automated gas control can reduce consumption of anesthetic vapor by one-third in pediatric anesthesia.

BACKGROUND: Many modern anesthetic machines offer automated control of anesthetic vapor. The user simply sets a desired end-tidal concentration and the machine will manipulate the vaporizer and gas flow rates to obtain and maintain the preset target. Greater efficiency, and more accurate delivery of anesthetic vapor have been documented across multiple machines within the adult setting however, there is little evidence for their use in children.

AIMS: The aim of this study was to compare the consumption of sevoflurane using the Maquet Flow-i anesthesia machine (Maquet, Solna, Sweden) in automatic gas control mode vs manual mode in pediatric anesthesia. The primary outcome measure is rate of sevoflurane use.

METHOD: Data logs were collected from our three Maquet Flow-i anesthesia machines over a 4-week period. We compared the rate of sevoflurane use when in manual mode vs cases where the automatic gas control mode was used. We also examined each automatic gas control case to determine whether percentage of anesthesia time in this mode correlated significantly with average rate of sevoflurane consumption.

RESULTS: Sevoflurane was the primary anesthetic used in 220 cases, comprising over 230 hours of anesthesia time. Of these, 36 cases were identified as automatic gas control cases and 184 as manual cases. Consumption of sevoflurane liquid in mL/min was significantly lower in automatic gas control cases (median 0.46, IQR 0.32-0.72 mL/min for automatic gas control; median 0.82, IQR 0.62-1.17 mL/min for manual; P < 0.001 by Wilcoxon Rank Sum test). For a case of median duration (49 minutes), average rate of sevoflurane liquid consumption was 0.54 mL/min for automatic gas control cases vs 0.81 mL/min for manual cases, a reduction of 33% (bootstrapped 95% CI 0.21-0.61 mL/min, P < 0.001).

CONCLUSION: Maquet's Flow-i automatic gas control mode reduced use of sevoflurane an average of one-third in a pediatric anesthesia setting.