The aim of this study was to evaluate the effect of continuous infusion of ondansetron compared with bolus injection on the incidence of postoperative nausea and vomiting (PONV) in intravenous, patient-controlled analgesia (PCA).

Sixty three women undergoing laparoscopic-assisted vaginal hysterectomy were randomly allocated according to the method of ondansetron administration: bolus injection of ondansetron (8 mg) after the operation (Bolus group, n = 21); continuous infusion after ondansetron (8 mg) mixed to PCA (PCA 8 mix group, n = 22); and continuous infusion after ondansetron (16 mg) mixed to PCA (PCA 16 mix group, n = 20). The PONV were measured at 1 hr, 6 hr, 24 hr and 48 hr after operation and pain scores (visual analog scale, VAS) were checked.

The incidence of PONV during 48 hr in the Bolus group (23.8%) and PCA 16 mix group (20.0%) were significantly lower than PCA 8 mix group (54.5%) (P < 0.05). The three groups showed similar VAS pain scores.

Our results suggest that continuous infusion of ondansetron 16 mg is as effective as a bolus injection of ondansetron (8 mg) at preventing PONV in high-risk patients.