Does the duration of N2O administration affect postoperative nausea and vomiting?

Nausea and vomiting are the most frequent postoperative complications in the ambulatory surgical setting. In the present study, data were obtained from 184 adult ambulatory cosmetic surgery patients to determine if the use of nitrous oxide (N2O) was associated with an increased incidence of postoperative nausea and/or vomiting (PNV). Anesthesia was induced with thiopental and maintained with an opioid (fentanyl or sufentanil) and isoflurane with or without N2O. Data were analyzed statistically using the two-way chi-square test and the Fisher Exact Test. The major finding was that the incidence of PNV was directly related to the duration of anesthesia in the patients who received N2O, but not in those who were N2O-free. Anesthesia times and the percentages of patients who exhibited PNV in the N2O-free and N2O-treated groups, respectively, were: (1) less than 1 hour, 0% and 6.3%; (2) between 1.0 and 1.9 hours, 35.3% and 36.8%; (3) between 2.0 and 2.9 hours, 24.2% and 66.7% (p = .06); (4) between 3.0 and 5.3 hours, 35% and 100% (P less than .05). Thus, avoidance of N2O in ambulatory cosmetic surgery cases lasting 3, and quite probably 2 or more hours in which general anesthesia is maintained with a synthetic opioid and isoflurane appears to reduce the likelihood that these short-stay patients will experience PNV.