Forest plot for the number of patients with post-operative nausea and vomiting.

<p>The plot displays the study, sample size, weighted risk ratio (RR), confidence interval (CI), and P value. Meta-analysis indicates dexmedetomidine significantly decrease the number of patients with post-operation nausea and vomiting compared with the placebo group. The square shown for each study (first author and year of publication) is the RR for individual trials, and the corresponding horizontal line is the 95% CI. The diamond is the pooled RR with the CI. The different sizes of squares indicate the weight the individual trials had in the analysis, taking into account sample size.