Study objective: To compare the intraoperative conditions and postoperative recovery of patients following the use of either propofol-nitrous oxide (N2O) or enflurane-N2O for maintenance of outpatient anesthesia.

Design: Randomized, single-blind study.

Setting: University hospital outpatient surgery center.

Patients: 61 ASA physical status I and II, healthy female outpatients undergoing laparoscopic surgery.

Interventions: Patients were randomly assigned to one of three anesthetic regimens. Group 1 (control) received thiopental sodium 4 mg/kg intravenously (i.v.), followed by 0.5% to 1.5% enflurane and 67% N2O in oxygen (O2). Group 2 received propofol 2 mg/kg i.v., followed by 0.5% to 1.5% enflurane and 67% N2O in O2. Group 3 received propofol 2 mg/kg i.v., followed by propofol 50 to 160 micrograms/kg/min i.v. and 67% N2O in O2. All patients received succinylcholine 1 mg/kg i.v. to facilitate tracheal intubation and atracurium 10 to 20 mg i.v. to provide adequate relaxation during the maintenance period.

Measurements and main results: Recovery from anesthesia was assessed by a research nurse who was unaware of the anesthetic technique used. The mean +/- SD time to eye opening was significantly longer in the thiopental-enflurane-N2O group (Group 1) than in the propofol-propofol-N2O group (Group 3) (6.1 +/- 2.5 minutes vs. 3.5 +/- 2.8 minutes, respectively). In addition, the mean time to respond to verbal commands was significantly shorter in the propofol induction groups compared with the thiopental induction group. However, the use of enflurane versus propofol for maintenance of anesthesia did not significantly prolong the time from arrival in the recovery room to sitting, tolerating oral fluids, walking, or being judged "fit for discharge." There were no differences among the three groups with respect to postoperative pain or analgesic requirements. Finally, patients who received enflurane for maintenance of anesthesia had a significantly higher frequency of nausea and vomiting than the propofol maintenance group.

Conclusion: Induction of anesthesia with propofol is associated with a more rapid emergence from anesthesia than induction with thiopental. Maintenance of anesthesia with enflurane did not prolong recovery compared with maintenance with propofol, but enflurane was associated with increased frequency of postoperative nausea and vomiting.