CRD Summary: The authors apparently concluded that combination treatments to prevent postoperative vomiting in children were superior to single-drug treatments and that a 5-hydroxytryptamine-receptor antagonist combined with dexamethasone or droperidol reduced vomiting by about 80%. Given the methodological problems in the review, including the limited search, failure to assess study quality and use of indirect comparisons, the results may not be reliable.

[Interventions used included ondansetron, tropisetron, granisetron, dolasetron, dexamethasone and droperidol, alone or in combination.]

CRD Commentary: The objectives and inclusion criteria of the review were clear, but the reason for the exclusion of a number of studies was not explained clearly. The search was limited to one database and it did not appear that efforts were made to locate unpublished studies, so studies may have been missed and the review may have been prone to publication bias. It was unclear whether the search was restricted by language. The search dates were not reported. The processes used to select studies and extract data were not described and so it was unclear whether steps were taken to minimise the risk of reviewer bias and error by having more than one reviewer make decisions independently. It did not appear that study validity was assessed. These factors make it difficult to evaluate the reliability of the evidence presented. The authors used a Bayesian meta-analysis, but did not appear to have used standard Bayesian meta-analysis techniques or software, and without presenting forest plots or results for each individual study it was difficult to assess the appropriateness of the methods. There was no assessment of statistical heterogeneity. Indirect comparisons were used, although the authors acknowledged the limitations of these methods. No clearly stated conclusion was reported. Given the methodological problems in the review, including the limited search, failure to assess study quality and use of indirect comparisons, the results may not be reliable.