Safety and efficacy of low-dose dexmedetomidine combined with midazolam for MRI in children aged 1–3 years: a randomized controlled trial

Cardiovascular adverse reactions and oversedation induced by intranasal dexmedetomidine are dose-dependent. Previous studies have shown that intranasal dexmedetomidine at 1 μg/kg, combined with oral midazolam at 0.5 mg/kg, provides effective preoperative sedation in children. Our study aimed to assess whether low-dose dexmedetomidine combined with midazolam provides effective sedation for children undergoing MRI. This study enrolled 304 children, who were randomly assigned to the DEX 1.0 group (0.5 mg/kg midazolam plus 1 μg/kg dexmedetomidine) or the DEX 1.5 group (0.5 mg/kg midazolam plus 1.5 μg/kg dexmedetomidine). The primary outcome was the first-time successful sedation rate, defined as achieving an UMSS score ≥ 2 within 30 min of initial drug administration and completing the examination uneventfully. The success rates for first-time sedation were 73.03% in the DEX 1.0 group and 76.32% in the DEX 1.5 group, with no significant difference between the groups. ( P = 0.510). The average sedation onset time for children with first-time successful sedation was under 20 min in both groups ( P = 0.316). After remedial sedation with DEX, a total of 302 children successfully completed the MRI examination. The DEX 1.5 group had a shorter recovery time, which was statistically significant ( P = 0.014). Heart rate decreased after the examination in both groups, and these reductions were statistically significant in both the DEX 1.0 and DEX 1.5 groups (both P < 0.05). However, the between-group difference in the magnitude of heart rate changes was not statistically significant ( P = 0.111). In this study, the two low-dose intranasal dexmedetomidine protocols achieved similar sedation success rates and had comparable adverse event profiles. registered with the Chinese Clinical Trial Registry (ChiCTR2200058882) on 18/04/2022.