The impact of nitrous oxide on postoperative nausea and vomiting after desflurane anesthesia for breast surgery.

A recent meta-analysis showed that omitting N2O significantly reduced postoperative vomiting (POV) compared with a N2O regime. Our study was designed to evaluate the effect of the combination of desflurane with N2O versus desflurane alone on postoperative nausea and vomiting (PONV) in a subgroup of female patients and PONV was considered as the primary endpoint. After approval of the local Ethics Committee and informed consent 60 female in-patients (ASA I & II), aged 18-65 y, scheduled for breast surgery with a duration of 1-3 h were included. Obese patients or patients with a history of PONV and motion sickness were excluded. No prophylactic anti-emetic therapy was allowed during the study. Patients received a standardized anesthetic technique consisting of propofol for induction, vecuronium and fentanyl for intubation, followed by desflurane with or without N2O (randomisation list) and fentanyl supplements if required for maintenance of anesthesia. At the end of anesthesia PONV was recorded during 24 h in different periods. There were no significant differences between the groups with respect to demographic data and duration of anesthesia. In addition, there were no significant differences in the amount of intraoperative fentanyl or postoperative narcotics. The incidence of PONV was significantly higher in the group of patients receiving desflurane in N2O-O2 mixture compared with the group receiving desflurane in AIR-O2 mixture. The combination of desflurane with N2O in female patients undergoing breast surgery is associated with a significantly higher incidence of PONV and a higher need of antiemetic drugs, when compared to a N2O free regime.