Nitrous oxide does not improve sevoflurane induction of anesthesia in adults

Study Objective: To compare the characteristics of sevoflurane induction with and without the addition of nitrous oxide (N2O) using tidal breathing inhalation induction without priming of the breathing circuit. Design: Randomized, double-blind study. Setting: Operating rooms of an ambulatory surgery suite at a university hospital. Patients: 60 ASA physical status I and II adult patients undergoing elective surgery. Interventions: Patients were randomized into two groups. During induction, Group I received 8% sevoflurane in N2O 4L/min and oxygen (O-2) 2L/min; Group 2 received 8% sevoflurane in O-2 6L/min. The time to cessation of finger tapping was used as the main index for induction time. Any adverse effects such as coughing, apnea, excessive oral secretions, laryngospasm, excitatory movements, and hemodynamic changes were also noted. Measurements and Main Results: There were no significant differences in the induction (Group 1: 62.0 vs. Group 2: 60.0 sec), number of breaths taken to this time (15.0 vs. 14.0), expired sevoflurane concentration at this time (3.4 vs. 3.2%), and time to Laryngeal Mask Airway(TM) insertion (160.0 vs. 195.0 sec). The frequencies of induction-related adverse events were similar in both study groups. Conclusion: The addition of N2O does not confer any clinically significant advantage in this method of sevoflurane induction in adults. (C) 2002 by Elsexier Science.