Safety Evaluation of Propofol Sedation for Magnetic Resonance Imaging in Pediatric Patients

Magnetic resonance imaging in children, especially under 6 years of age, is often performed under sedation. Propofol is a common drug used in this settings. In our institution, sedation is most often done by a propofol bolus of 2-5 mg/kg in order to reach a deep level of sedation as defined by Coté et al. If judged necessary by the attending anaesthesiologist, a additional propofol bolus of 0.5-1 mg/kg may be given. For longer lasting exams, the attending anaesthesiologist can chose to use a continuous infusion of propofol. The investigators will review the charts of 4 month of magnetic resonance imaging, which will give us a cohort of about 100 patients. Baseline characteristics, detailed sedation technique used will be recorded. Adverse events defined as: * Oxygen desaturation measured by transcutaneous oximetry SpO2≤94% * hypercapnia measure by end-tidal CO2 \>45 mm Hg * movement of the patient Assuming a non-normal distribution (tested by a Kolmogorov-Smirnov test), variables will be reported as median and interquartile range. Statistical tests will be done by non-parametric tests, Mann Whitney U. Non continuous variables will be analyzed by a Chi-square test.