Sedative, haemodynamic and respiratory effects of dexmedetomidine in children undergoing magnetic resonance imaging examination: preliminary results

Background. We evaluated the sedative, haemodynamic and respiratory effects of dexmedetomidine and compared them with those of midazolam in children undergoing magnetic resonance imaging (MRI) procedures. Methods. Eighty children aged between 1 and 7 yr were randomly allocated to receive sedation with either dexmedetomidine (group D, n=40) or midazolam (group M, n=40). The loading dose of the study drugs was administered for 10 min (dexmedetomidine 1 mu g kg(-1) or midazolam 0.2 mg kg(-1)) followed by continuous infusion (dexmedetomidine 0.5 mu g kg(-1) h(-1) or midazolam 6 mu g kg(-1) min(-1)). Inadequate sedation was defined as difficulty in completing the procedure because of the child's movement during MRI. The children who were inadequately sedated were given a single dose of rescue midazolam and/or propofol intravenously. Mean arterial pressure (MAP), heart rate (HR), peripheral oxygen saturation (Sp(o2)) and ventilatory frequency (VF) were monitored and recorded during the study. Results. The quality of MRI was significantly better and the rate of adequate sedation was higher in group D than in group M (P < 0.001). In group D, the requirement for rescue drugs was lower and the onset of sedation time was shorter than in group M (P < 0.001). MAP, HR and VF decreased from baseline during sedation in both groups (P < 0.001). Conclusions. Dexmedetomidine provided adequate sedation in most of the children aged 1-7 yr without haemodynamic or respiratory effects during MRI procedures.