 The sample size was predetermined. We expected a 20 difference in the incidence of nausea and vomiting between groups. The error alpha error was set at 0.05 and beta error at 0.20; n 103 patients for each group was considered adequate, according to a power analysis. Results were expressed as percentages and as the mean standard deviation SD. Students t test and the chi squared test were used for the analysis of quantitative and qualitative data, respectively. Differences were considered statistically significant at p 0.05. 