Propofol anaesthesia and postoperative nausea and vomiting: quantitative systematic review of randomized controlled studies

We have analysed randomized controlled studies which reported the incidenceof postoperative nausea and vomiting (PONV) after propofol anaesthesiacompared with other anaesthetics (control). Cumulative data of early (0-6h) and late (0-48 h) PONV were recorded as occurrence or non-occurrence ofnausea or vomiting. Combined odds ratio and number- needed-to-treat werecalculated for propofol as an induction or maintenance regimen, early orlate outcomes, and different emetic events. This was performed for allcontrol event rates and within a range of 20-60% control event rates. Weanalysed 84 studies involving 6069 patients. The effect of propofol on PONVwas dependent mainly on the method of administration, time of measurementand range of control event rates. When all studies were included thenumber-needed-to-treat to prevent PONV with propofol was more than 9 whenused for induction of anaesthesia and at best 6 when used for maintenance.Within the 20- 60% control event rate range, best results were achievedwith propofol maintenance to prevent early PONV: the number-needed-to-treatto prevent early nausea was 4.7 (95% confidence interval 3.8-6.3), vomiting4.9 (4-6.1) and any emetic event 4.9 (3.7-7.1). Within the 20- 60% controlevent rate, of five patients treated with propofol for maintenance ofanaesthesia, one will not vomit or be nauseated in the immediatepostoperative period who would otherwise have vomited or been nauseated.This may be clinically relevant. In all other situations the differencebetween propofol and control may have reached statistical significance butwas of doubtful clinical relevance. Treatment efficacy should beestablished within a defined range of control event rates for meaningfulestimates of efficacy and for comparisons.