[Ondansetron as prophylaxis for postoperative nausea and vomiting. A prospective randomized double-blind comparative...

Ondansetron, a selective 5-HT3 receptor antagonist, has recently been shown, in a dose of 8 mg, to be superior to 1.25 mg droperidol in preventing postoperative vomiting. There are indications that a dose of 4 mg of ondansetron may be just as effective in reducing postoperative nausea and vomiting as a dose of 8 mg. The aim of this study was to evaluate the efficacy and the adverse effects of 4 mg ondansetron in the prevention of postoperative nausea and vomiting compared to droperidol in patients undergoing surgery with inhalation anaesthesia supplemented with alfentanil. METHODS. Following institutional approval, 40 ASA physical status I and II women scheduled for minor gynaecological surgery gave informed consent to participate in this randomized, double-blind comparative study. Five minutes before induction of general anaesthesia, 20 patients received a single intravenous (i.v.) dose of 4 mg of ondansetron and the remaining 20 received 1.25 mg droperidol i.v. Anaesthesia was induced with 2.1-4 mg/kg of thiopental and 0.1 mg of alfentanil i.v. and maintained with 65% nitrous oxide and 1.5%-3% enflurane in oxygen. On pain stimuli another 0.2-0.4 mg of alfentanil was given. Total effective antiemetic response was defined as the absence of nausea and vomiting for 24 h postoperatively. The incidence of nausea, vomiting and the number of patients showing total antiemetic response as well as the incidence of adverse effects were compared with the chi 2 test and P < 0.05 was considered significant. RESULTS. Patients were similar with respect to age, height, body weight and total anaesthetic agents received. Duration of anaesthesia and the time until awakening was not significantly different among groups. Postoperatively 7 out of 20 patients given 4 mg of ondansetron and 3 out of 20 patients with droperidol vomited (n.s.). The incidence of nausea was 11 out of 20 in the ondansetron group, and 4 out of 20 in the droperidol group (P < 0.05). Sixteen patients in the droperidol group and 8 patients in the ondansetron group showed a total effective antiemetic response (P < 0.05). Postoperative sedation and well-being scores did not differ significantly among groups. CONCLUSION. Our results show that for the prevention of postoperative nausea and vomiting 4 mg of Ondansetron was inferior to 1.25 mg of droperidol. The drugs were given intravenously prior to general anaesthesia for minor gynaecological surgery with nitrous oxide and enflurane in oxygen supplemented with small boluses of alfentanil.