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

Abstract

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 pre set target. The aim of this software is to allow greater efficiency, and more accurate delivery of anesthetic vapor during anesthesia. These benefits have been documented across multiple machines within the adult setting^(1,2,3,4) however there is little evidence for their use in children.

Aim

To compare the consumption of sevoflurane using the Maquet Flow‐i anesthesia machine (Maquet, Solna, Sweden) in automatic gas control (AGC) mode versus 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 four‐week period. We compared the rate of sevoflurane use when in manual mode versus cases where AGC mode was used. We also examined each AGC 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 AGC cases and 184 as manual cases.

Consumption of sevoflurane liquid in ml/min was significantly lower in AGC cases (median 0.46, IQR 0.32 to 0.72 ml/min for AGC; median 0.82, IQR 0.62 to 1.17 ml/min for manual; p<0.001 by Wilcoxon Rank Sum test). For a case of median duration (49minutes), average rate of sevoflurane liquid consumption was 0.54 ml/min for AGC cases versus 0.81 ml/min for manual cases, a reduction of 33% (bootstrapped 95%CI 0.21 to 0.61 ml/min, p<0.001).

We also identified an inverse correlation between the rate of sevoflurane consumption and the percentage of the anesthesia time for which AGC mode was utilized, increasing the use of automatic gas control from 30% to 90% of anesthetic time was associated with a fall in rate of sevoflurane liquid consumption from 0.73 ml/min to 0.35 ml/min, a reduction of 52% (bootstrapped 95%CI 0.17 to 0.66 ml/min, p<0.001 for the trend).

Conclusion

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

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