Background: Nitrous oxide is decreasingly used due to theoretically considered complications. However, we have not had clinically obvious complications for many 
decades. The present study was done to investigate usefulness of nitrous oxide in sevoflurane anesthesia in terms of hemodynamic changes at induction and postoperative complications. 

Methods: One hundred and twenty patients for body surface surgery were enrolled. Anesthesia was induced with sevoflurane 5% for 5 min. or 8% for 3 min. with or 
without 50% nitrous oxide and maintained with sevoflurane with or without 50% nitrous oxide (5%GOS, 8%GOS, 5%OS, and 8%OS groups, each 30 patients).  Blood pressure, heart rate, loss of eyelash reflex and verbal response, sevoflurane consumption, time to emergence, and postoperative complications including nausea and vomiting were compared among the groups.

Results: Time to loss of eyelash reflex and verbal response were significantly shorter in 5% GOS and 8% GOS than those in 5% OS and 8% OS, respectively. Sevoflurane consumption was significantly larger with 5% OS than 5% GOS. Time to extubation was not different. Changes in blood pressure were significantly higher in 8% OS than that in 8% GOS. Increase in heart rate by intubation was significantly larger in 5% OS and 8% OS than those in 5% GOS and 8% GOS, respectively. The frequency of nausea and vomit were not different among the groups. No clinically obvious complication was observed for postoperative one-month period.

Conclusion: In sevoflurane anesthesia, nitrous oxide decreased hemodynamic changes at induction and intubation, and did not induce any clinically obvious complications. 

Keywords: Nitrous oxide; Sevoflurane; Hemodynamics; Complication