Desflurane and sevoflurane use during low- and minimal-flow anesthesia at fixed vaporizer settings

Abstract

Background: The pharmacokinetics for sevoflurane and desflurane makes them suitable for low-flow anesthesia. The aim of the present study was to assess the use of desflurane and sevoflurane at constant vaporizer settings and fixed low fresh gas flows.

Methods: One hundred ASA 1-2 patients undergoing elective laparoscopic surgery were randomized into 4 groups (25 patients each): a fixed fresh gas flow 1.0 or 0.5 L/min with desflurane (D1.0 and D0.5) or sevoflurane (S1.0 and S0.5) throughout anesthesia. A fixed vaporizer setting, sevoflurane 6% and desflurane 18% was used during wash-in. Time to reach 1 and 1.5 minimum alveolar concentration (MAC), emergence and gas consumption from start to end of surgery was studied.

Results: Time to reach 1 MAC age adjusted desflurane or sevoflurane was D0.5 8.5±1.7, D1.0 3.7±0.7, S0.5 15.2±2.4 and S1.0 6.2±1.3 minutes, respectively (P<0.001), and times to increase from 1 to 1.5 MAC differed also significantly. Desflurane anesthesia was associated to significantly shorter time to extubation 6.7±2.3 vs. 10±2.3 minutes for sevoflurane (P<0.001). The amount of agent consumed g/min. was significantly reduced for both 0.5 L/min groups: 30% less for desflurane and 19% for sevoflurane.

Conclusions: We found an almost twice as rapid wash-in with desflurane and expectedly faster emergence. Gas consumption was lower at 0.5 L/min than it was at 1 L/min for both gases studied however most pronounced for desflurane. Desflurane has clear advantages for minimal fresh gas flow anesthesia.