Sevoflurane for outpatient anaesthesia: Comparison with isoflurane

A multicenter, randomized, comparative phase III study evaluating the effect of sevoflurane versus isoflurane in adult outpatients was performed. The aim of the study was to compare (1) maintenance of anaesthesia and (2) how rapidly and easily the patients emerge from the anaesthetic and recover. Methods. Outpatients were included who underwent scheduled surgical procedures of an anticipated duration of up to 3 h and an anticipated length of hospitalization of less than 24 h post-anaesthesia. Five hundred patients were randomly selected to receive either sevoflurane (n = 247) or isoflurane (n = 253), each administered with oxygen (30-50%) in nitrous oxide. Efficacy was evaluated through the measurement of times of recovery parameters and tests like the objective pain-discomfort scale, the visual analogue scale, and the digit symbol substitution test. Safety was evaluated by monitoring adverse experience, clinical laboratory and non-laboratory testing and physical assessments. Results. No statistical differences were observed between the two treatment groups with respect to demographics and ASA class. All study drug concentrations during each anaesthetic phase were statistically lower in the sevoflurane (average concentration 0.61 MAC) compared to the isoflurane (average concentration 0.70 MAC) group. The mean time to emergence was statistically shorter in the sevoflurane group (8.2 min) than in the isoflurane group (9.3 min). The mean time to response to commands (8.5 min vs 9.8 min) and the mean time to orientation (10.6 min vs 13.0 min) were also statistically shorter in the sevoflurane than in the isoflurane group. The EEG results showed a faster decrease in delta activity and a faster increase in alpha activity in the sevoflurane group than in the isoflurane group, indicating faster awakening. No statistical differences were observed between the two treatment groups for the mean time to any of the remaining postanaesthesia events. Bradycardia was observed in a statistically higher percentage of patients in the sevoflurane group (6%) than in the isoflurane group (2%). No other statistical differences were observed between the two treatment groups concerning the incidence of study drug-related adverse experience. The most common adverse experiences were nausea and vomiting. At all postanaesthesia time points, higher serum inorganic fluoride concentrations were observed in the sevoflurane (maximum 30.2 mu mol/1) than in the isoflurane group. No clinical or laboratory renal insufficiency was noted. Eighty-seven percent of patients in the sevoflurane group would request the same anaesthetic technique compared to only 79% of patients in the isoflurane group. Conclusions. Sevoflurane was as safe as isoflurane for anaesthesia in adult outpatients. Patients who received sevoflurane had statistically significantly shorter recovery parameters than isoflurane patients.