THE DOSE OF PROPOFOL REQUIRED TO PREVENT CHILDREN FROM MOVING DURING MAGNETIC-RESONANCE-IMAGING

Background. Intravenous propofol offers several advantages as an anest hetic for children undergoing magnetic resonance imaging. However, the dose of propofol required to prevent movement during magnetic resonan ce imaging is likely to be less than that required for surgical anesth esia. Methods. Thirty children between the ages of 1 and 10 years, und ergoing elective magnetic resonance imaging as outpatients were random ly assigned to receive a propofol infusion at a rate of 50, 75, or 100 mug . kg-1 . min-1 during the imaging procedure. Anesthesia was induc ed with inhalation of halothane, nitrous oxide, and oxygen, and a 2 mg . kg-1 loading dose of propofol. Immediately after insertion of an in travenous catheter, inhaled anesthetics were discontinued and the prop ofol infusion started. The children then were observed for movement du ring the scan. Results: There were no significant differences among th e three groups with respects to mean age (4.4 +/- 2.0 yr), weight (17. 6 +/- 5.1 kg), induction time (11 +/- 3 min), scan duration (55 +/- 26 min), or recovery time (30 +/- 8 min). Five of ten patients who recei ved 50 mug.kg-1.min-1 moved during the scan, three of ten patients who received 75 mug . kg-1 . min-1 moved, and none of the children who re ceived 100 mug - kg-1 . min-1 moved. Two patients experienced a decrea se of arterial oxygen saturation to less than 95% after receiving the initial bolus of propofol. The arterial oxygen saturation returned to normal within 15 s without specific treatment other than continued sup plemental oxygen. There were no episodes of hypoxemia during image acq uisition. None of the children experienced nausea or vomiting. Conclus ions: Following induction of anesthesia with halothane, nitrous oxide, and a 2 mg . kg-1 loading dose of propofol, infusion of propofol at a rate of 100 mug-kg.1-min 'effectively prevents children from moving d uring elective magnetic resonance imaging. A transient decrease in art erial oxygen saturation can occur after the initial bolus of propofol. Recovery from anesthesia is rapid and without nausea or vomiting.