Abstract: Objective · To evaluate the efficacy and safety of sedation using oral midazolam in combination with intranasal dexmedetomidine for magnetic resonance imaging (MRI) in paediatric patients. Methods · A total of 186 children aged 3–8 years undergoing MRI in Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, from March 2019 to July 2019, were randomly assigned to two groups, who received either oral 50 mg/kg chloral hydrate combined with 2 μg/kg intranasal dexmedetomidine (chloral hydrate group, n=93) or oral 0.3 mg/kg midazolam combined with 2 μg/kg intranasal dexmedetomidine (midazolam group, n=93). The efficacy and safety of the sedative regimens were evaluated based on the successful sedation rate, sedation onset time, wake-up time, total sedation time and the incidence of clinical side effects. Results · The successful sedation rates were 98.9% and 94.6% in chloral hydrate group and midazolam group, respectively, with no significant difference (P>0.05). The sedation onset time was 20.0 (10.0, 20.0) min in midazolam group, which was longer than that in chloral hydrate group (P=0.000). The wake-up time was 15.0 (3.0, 31.8) min and the total sedation time was 68.0 (58.0, 82.0) min in midazolam group, both of which were significantly shorter than those in chloral hydrate group (P=0.000, P=0.001). The sedation in midazolam group was better accepted by children who did not experience nausea or vomiting. Hypotension and bradycardia were rare and did not require intervention in either group. Conclusion · Oral midazolam combined with intranasal dexmedetomidine is better accepted by the paediatric patients and the wake-up time of it is shorter, which may be used effectively and safely for sedation during paediatric MRI procedures．

Key words: midazolam, dexmedetomidine, magnetic resonance imaging (MRI), paediatric patient, sedation