The drug cost difference was calculated from the management model, assuming 629 patients a year, and different types of scan. The total costs were:Propofol, $2590.43; Barbiturates, $860.67. This gave a cost difference for 629 patients a year of $1729.76, adjusted to $1600.76 if waste of drug was considered. The use of propofol reduced nursing time in the PACU, causing a saving of $5086.67 a year, when the pediatric MRI model was used. Therefore, overall a yearly saving of $3227.91 was obtained with propofol. Some cost components regarding radiologic and anaesthesia costs were excluded from the analysis since they were presumed to be the same for both groups.