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

Background. Intravenous propofol offers several advantages as an anesthetic for children undergoing magnetic resonance imaging. However, the dose of propofol required to prevent movement during magnetic resonance imaging is likely to be less than that required for surgical anesthesia. Methods. Thirty children between the ages of 1 and 10 years, undergoing elective magnetic resonance imaging as outpatients were randomly 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 induced with inhalation of halothane, nitrous oxide, and oxygen, and a 2 mg . kg-1 loading dose of propofol. Immediately after insertion of an intravenous catheter, inhaled anesthetics were discontinued and the propofol infusion started. The children then were observed for movement during the scan. Results: There were no significant differences among the 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 received 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 received 100 mug - kg-1 . min-1 moved. Two patients experienced a decrease 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 supplemental oxygen. There were no episodes of hypoxemia during image acquisition. None of the children experienced nausea or vomiting. Conclusions: 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 during elective magnetic resonance imaging. A transient decrease in arterial oxygen saturation can occur after the initial bolus of propofol. Recovery from anesthesia is rapid and without nausea or vomiting.