Comparative Study of Automated End Tidal Control Versus Manual Fresh Gas Flow Adjustment with Respect to Gas Usage and Delivery during Low Flow Anesthesia

Author(s): Kanika Arora, Adarshchandra Swami, Padma Puppala, Ankita Rai

Background: During low-flow manually-controlled anesthesia (MCA) the anesthetist keeps adjusting end-tidal oxygen (EtO2) and anesthetic concentrations (EtAA) constantly to ensure adequate and safe anesthesia. This study was performed to compare End Tidal Control and Manual Control of Fresh gas flow during low flow anesthesia.

Methods: Study was conducted on 84 ASA I and II patients 18-65 years age, of either sex, requiring general anesthesia for more than 2 hours. In MCA group (n = 42) target end-tidal desflurane (4%) and EtO2 concentrations (≥ 35%) were manually controlled by the anesthetist. In EtCA group (n = 42), same anesthetic machine with additional end-tidal control feature was used to reach same targets.

Results: The median desflurane consumption was 15.71 ml and 16.71 ml in ETCA and MCA respectively (p value =0.002) after one hour and 28.71ml and 32.98 ml in ETCA and MCA respectively (p value <0.001 ) after two hours. In ETCA group, median number of adjustments was 3.83 after one hour and 7 after two hours (p – value <0.001). Cost of anesthetic agent consumed after one hour in ETCA group was Rs 562.57 and MCA group was Rs 598.37 (p value<0.002) . After two hours, cost of anesthetic agent consumed in ETCA group was Rs 1008.367 and in MCA group was Rs 1173.729 (p value <0.001).

Conclusion: Automatic implementation of low flow anesthesia using end tidal control is a good system for conserving the consumption of gases and reducing the number of adjustments needed to maintain depth of anesthesia.

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