Statistics Assuming that MB pre-treatment would reduce the requirement of propofol by 25%, power analysis with alpha = 0.05, beta = 0.8, shows that we would need to study at least 10 patients in each group. The computer program SAS 8.0 for Windows will be used for all data analyses. Parametric data will be analysed by two-way ANOVA. Unpaired Student t-tests, Chi-squared tests and Fisher's exact probability tests will be used as appropriate for comparison between groups. All values are expressed as mean (M), standard deviation (SD) and statistical significance will be accepted at p < 0.05.