Prophylactic ondansetron for postoperative emesis. Meta-analysis of its effectiveness in patients with previous history of postoperative nausea and vomiting

Background: The objective of this study was to compare, by means of meta-an alysis, the postoperative antiemetic efficacy of ondansetron in patients wi th and without antecedents of postoperative nausea and vomiting. Methods: MEDLINE and EMBASE databases were searched for randomised placebo- controlled trials which evaluated the antiemetic effectiveness of 4 mg and 8 mg intravenous doses of prophylactic ondansetron in adult patients. A fur ther selection was with respect to those studies which noted the patient's previous history of postoperative nausea and vomiting (PH-PONV) and, for th e meta-analysis, the patients were divided into two sub-groups: those with (PH-PONV +) and those without a previous history of postoperative nausea an d vomiting (PH-PONV -). Absence of vomiting was used as the index of effect iveness. Results: Twenty-one trials involving 3984 patients (2446 in ondansetron gro ups and 1538 in placebo groups; 1163 PH-PONV(+) patients and 2821 PH-PONV(- ) patients) met the selection criteria. The effectiveness of the 4 mg dose of ondansetron was: OR (95% CI) = 2.40 (1.77-3.26) vs. 2.71 (2.23-3.30) for the patients of PH-PONV(+) and PH-PONV(-) sub-groups, respectively. For th e 8 mg dose, the effectiveness of ondansetron was: PHPONV(+) = 4.21 (2.66-6 .66) and PH-PONV(-) = 2.61 (1.81-3.59). For neither of the doses evaluated was there any significant statistical difference between the sub-groups. Conclusions: The effectiveness of ondansetron in the prevention of postoper ative vomiting is not affected by the patients' PHPONV.