Ketamine dosing for sedation during repeated radiotherapy sessions in children

We report the analysis of ketamine doses needed and the recovery times in pediatric oncology patients undergoing repeated radiotherapy sessions. In a single-blind prospective study design, thirty-three pediatric patients undergoing radiotherapy due to oncologic disorders received 2 mg/kg ketamine and 10 μg/kg atropine intravenously and the rescue drug to be administered was ketamine at 0.5 mg/kg when the sedation level was inadequate. Total ketamine consumption, additional doses, and recovery time were recorded. Data of 635 consecutive radiotherapy sessions were evaluated. There was no significant alteration in total ketamine consumption required to complete the radiotherapy periods during consecutive procedures (P > 0.05). However, the recovery times started to decrease by the fourth session (P = 0.02) and continued to decrease onwards during the whole study period (P = 0.001). The mean of the first recovery time was 13.68 ± 3.99 min, whereas the mean of the last recovery time was 7.66 ± 6.35 min. A requirement for an incremental increase in ketamine dose after subsequent administrations was not detected, despite a significant decrease in recovery times being anticipated when ketamine is used repeatedly for sedative purposes in consecutive radiotherapy sessions.