Seventy RCTs recorded vomiting (4,074 patients), 61 RCTs recorded nausea (3,516 patients), and 17 RCTs recorded nausea and vomiting (742 patients).
The random-effects model produced only marginally wider confidence limits thn the fixed-effect model, with similar mean OR estimates. Only the results from the fixed-effect models were reported. It was not possible to subsequently determine the distribution across time of different patients' post-operative nausea and vomiting, due to insufficient clarity in the reporting of the results. For studies reporting more than one time interval, only the first was included in the analysis.
The OR observations for induction and maintenance with propofol, compared with other agents, were as follows for the defined subsets.
Vomiting data set.
Full data set: the OR was 0.267 (95% confidence interval, CI: 0.220, 0.325, P<0.0001), and the heterogeneity P was 0.045. Box plots suggested that all the comparator anaesthetics produced similar ORs in favour of propofol. Surgery type, opiate narcotic use, patient's age and nitrous oxide did not appear to influence the OR. The NNT was 7.1 (95% CI: 5.6, 9.7) and the fail-safe N was 3,090 trials.
Full data set, excluding the 0 to 24 hour follow-up trials (66 RCTs): the OR was 0.240 (95% CI: 0.198, 0.295, P<0.0001) and the heterogeneity P was 0.57.
Adults subset (57 RCTs): the OR was 0.288 (95% CI: 0.232, 0.357, P<0.0001) and the heterogeneity P was 0.16.
Children (13 studies): the OR was 0.174 (95% CI: 0.104, 0.289, P<0.0001) and the heterogeneity P was 0.06.
Comparator of isoflurane as maintenance (42 RCTs): the OR was 0.267 (95% CI: 0.205, 0.347, P<0.0001) and the heterogeneity P was 0.12.
Comparator of isoflurane as maintenance and propofol as induction (16 RCTs): the OR was 0.391 (95% CI: 0.247, 0.621, P<0.0001) and the heterogeneity P was 0.01.
Comparator of desflurane or sevoflurane asmaintenance (6 RCTs): the OR was 0.430 (95% CI: 0.244, 0.757, P=0.003) and the heterogeneity P was 0.17.
Opiate narcotic (45 RCTs): the OR was 0.275 (95% CI: 0.218, 0.348, P<0.0001) and the heterogeneity P was 0.09.
Nitrous oxide (51 RCTs): the OR was 0.250 (95% CI: 0.202, 0.309, P<0.0001) and the heterogeneity P was 0.12.
Nausea data set.
The common OR was 0.377 (95% CI: 0.316, 0.450, P<0.0001) and the heterogeneity P was 0.02. The NNT was 8.1 (95% CI: 6.3, 11.1) and the fail-safe N was 1,804 trials.
Nausea and vomiting data set.
The common OR was 0.374 (95% CI: 0.262, 0.535) and the heterogeneity P was 0.44. The NNT was 6.6 (95% CI: 4.6, 11.9) and the fail-safe N was 112 trials.