High-dose ondansetron regimen vs droperidol for morphine patient-controlled analgesia

We have performed a randomized, double-blind study comparing droperidol and high-dose ondansetron mixed with morphine for patient-controlled analgesia (PCA). To detect a reduction in the incidence of postoperative nausea and vomiting from 55% to 20% with a power of 80% at the P<0.05 level, 29 patients per group were required. We studied 60 healthy women undergoing abdominal hysterectomy, anaesthetized using a standard technique. Group D received a bolus dose of droperidol 1.25 mg at induction followed by droperidol 0.1 mg per 1 mg of morphine from the PCA system. Group O received a bolus dose of ondansetron 4 mg at induction followed by ondansetron 0.32 mg per 1 mg of morphine. This dose of ondansetron is more than double that studied previously. Mean nausea and vomiting scores at 4, 8, 12 and 24 h, mean time to first vomit, sedation scores, incidence of side effects, and doses of prochlorperazine did not differ between the groups. In group D, 24 patients did not vomit compared with 23 in group O. The only significant difference between the groups was increased morphine consumption in the ondansetron group up until 12 h after operation (P<0.05), but by 24 h this difference was not significant. The ondansetron regimen was more expensive (at local prices) by a factor of 27, and our results suggested no clinical advantage over droperidol.