Magnetic resonance imaging (MRI) is a widely used radiology technique with its unique noisy environment and a narrow pipe like appearance. However, it is very difficult for a child to remain motionless to avoid movement artefact, and get a qualified image. General anaesthesia or sedation is frequently required to eliminate motion artefacts and to attenuate anxiety during MRI in young children or in children with complex medical conditions. Propofol(PRO) and dexmedetomidine(DEX) are commonly used for maintaining anaesthesia and sedation, and both are safe and effective in children undergoing MRI with few component scan (e.g., brain) and of short duration (<1 h). Compared with pentobarbital, midazolam, and fentanyl techniques, propofol yields faster induction, shorter emergence, less duration in postanaesthesia care unit (PACU), and fewer interruptions during the MRI related to patient movement. However, arterial desaturation, hypotension and dose-dependent response of upper airway collapse (by inhibition of airway dilator muscle and of upper airway reflexes) occasionally occur with the propofol technique. In order to minimize these side effects, some authors recommend the combination with other drugs like midazolam, opioids, ketamine or dexmedetomidine. The increasing popularity of dexmedetomidine use in children stems from its ability to provide adequate procedural sedation with a relatively low risk of respiratory depression. In addition, dexmedetomidine is associated with a significantly lower need for artificial airway support during sedation for magnetic resonance imaging (MRI) in children with obstructive sleep apnea, compared to propofol.

Concomitant addition of two drugs can bring drug synergy effect on sedation and contributes to decreased risk of adverse effects. Therefore, by using combination regimen, it could provide short induction time, fast recovery, stable cardiorespiratory conditions, and rarely requires additional sedation, and therefore is safe and adequate for pediatric MRI sedation.

The goal of our study is to compare propofol (with and without ketamine) and dexmedetomidine based sedation regimens for pediatric MRI sedation with respect to several measures such as timeliness, safety profile, image and sedation quality outcomes, and parental satisfaction in children undergoing multicomponent MRI scan.