Propofol for Ambulatory Laryngomicrosurgery Using Bispectral Index Monitoring: Nitrous Oxide Does Not Significantly Affect Postanesthetic Recovery and Emetic Sequelae / 대한마취과학회지

ABSTRACT

BACKGROUND: Although nitrous oxide (N2O) is used commonly during anesthesia, the roles of N2O in postanesthetic recovery and emetic sequelae are not well established in the ambulatory surgery. The goal of this study was to compare outcomes in patients anesthetized with propofol/air versus propofol/N2O using BIS. METHODS: Patients for ambulatory laryngomicrosurgery were randomly allocated to the group of anesthesia with propofol/air (Air, n = 44) or propofol/67% N2O (N2O, n = 44). The target concentration of propofol was controlled to maintain the BIS values between 35 and 40. By the end of surgery, anesthetics were discontinued and the time to eyes-open (TTEO) on verbal command was measured. The BIS values, effect site concentration (ESC), and total propofol doses were measured at eyes-open. Time to first drink (TTD), walk (TTW), and PONV were evaluated by blinded observers in the phase II recovery room. All data were analyzed using the student t-test and the Chi-Square Test. RESULTS: In the Air group, TTEO was significantly shorter than in the N2O group (7.6+/-3.1 min vs 9.5+/-2.3 min) despite the higher ESC of propofol (1.8+/-0.4 mcg/ml vs 1.5+/-0.3 mcg/ml). The propofol doses, BIS scores at eyes-open, TTD and TTW, and the incidence of PONV were no different in the two groups. Females showed faster emergence from anesthesia than males in the operating room, but showed slower recovery in the phase II recovery room. CONCLUSIONS: N2O does not affect significantly postanesthetic recovery and emetic sequelae. Since N2O has no effect on BIS values, propofol doses may be titrated accordingly.