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

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.