Avoidance of nitrous oxide and increased isoflurane during alfentanil based anesthesia decreases the incidence of postoperative nausea.

Postoperative nausea and vomiting have been associated with the use of nitrous oxide. Alfentanil, when combined with nitrous oxide, also results in a high incidence of postoperative nausea and vomiting. To further define this emesis-potentiating effect of N2O, 119 patients were chosen for study and divided into two groups: group A (n = 59) was administered a mixture of alfentanil, N2O, and O2 with 0.25% isoflurane, group B (n = 60) was administered a mixture of oxygen, room air, isofluorane, and alfentanil. The incidence of postoperative nausea and vomiting was ascertained by a blinded observer in the recovery room. All 119 patients were scheduled for extra-abdominal procedures (excluding thoracotomial, intracranial, ophthalmologic, and middle ear surgery). Patients with a previous history of nausea and vomiting, hiatal hernias, reflux esophagitis, or morbid obesity were excluded. The incidence of vomiting was 5% (3/60) in group B and 15% (8/59) in group A (P = 0.067). Forty-four percent (26/59) of the patients in group A and 20% (12/59) in group B were nauseated postoperatively (P = 0.005). Our data suggest that elimination of N2O from alfentanil-based anesthetics lessens the incidence of nausea.