Fig. 2. The graph illustrates the incidence of side effects, the mean pain score, and the mean number of extra epidural bolus doses of each complex during the optimization procedure. Side effects are represented as the proportion of patients in which the epidural regimen investigated had to be discontinued because of any side effect (table 6). The pain score of each complex was calculated by computing the mean for each patient, using all observations on pain at rest and during cough, and calculating the average pain score for each regimen from the individual means of all patients. The mean pain score of each complex was then calculated from the mean scores of the corresponding regimens (fig. 1). The number of extra epidural bolus doses per hour was calculated by dividing the total number of bolus doses by the time during which the epidural mixture was infused.