Desflurane consumption with automated vapor control systems in two different anaesthesia machines. A randomized controlled study.

BACKGROUND In general anaesthesia practice a fresh gas flow of ≥ 0,5L/min is usually applied. Automated gas delivery devices are developed to reduce volatile anaesthetic consumption by limiting gas flow. This study aimed to compare desflurane consumption between automated gas control devices compared to conventional low flow anaesthesia in the Flow-I and Aisys anaesthesia machines, and to compare desflurane consumption between the two automated gas delivery devices. We hypothesised that desflurane consumption would be lower with automated gas delivery compared to conventional low flow anaesthesia, and that desflurane consumption could differ between the different gas delivery devices. METHODS We allocated 160 patients undergoing robot assisted laparoscopic surgery into four groups, Flow-I with automated gas control, Flow-I with conventional low flow (1 l/min), Aisys with end tidal gas control and Aisys with conventional low flow. Patients were maintained at MAC 0.7- 0.8. Desflurane consumption was recorded after 9, 30 and 60 minutes of anaesthesia. RESULTS After 60 minutes, compared to conventional low flow anaesthesia, automated gas delivery systems reduced desflurane consumption from 25.8 ml to 15.2 ml for the Aisys machine (p < 0.001) and from 22.1 ml to 16.8 ml for the Flow-I (p < 0.001). Time to MAC 0.7 and stable FGF was shorter with Aisys endtidal control compared to Flow-I automated gas control. CONCLUSION Under clinical conditions, we found a reduction in desflurane consumption when using automated gas delivery devices compared to conventional low flow anaesthesia. Both devices were reliable in use.