The role of nitrous oxide in postoperative nausea and recovery in patients undergoing upper abdominal surgery.

The effect of nitrous oxide on postoperative nausea/vomiting and alertness were studied in 50 patients undergoing elective upper abdominal surgery. The study period lasted 20 h. Patients were randomly assigned to receive thiopentone-fentanyl-isoflurane-pancuronium anaesthesia with either 70% nitrous oxide-oxygen (Group I) or air-oxygen (Group II). There were no differences between the groups regarding age, sex, weight or amount or per- and postoperative analgetics given. The mean inspiratory isoflurane concentrations were 0.6% and 1.15% in Groups I and II, respectively. The postoperative alertness was tested by a visual analogue scale (0-10) for 6 h postoperatively. Omitting nitrous oxide did not decrease the frequency of postoperative nausea, although the symptoms were milder in the air group. The patients without nitrous oxide were alert earlier, in spite of a higher isoflurane concentration: VAS from 5 to 8.7 vs from 2.8 to 6.9 during the first 6 postoperative hours.