Objective:To evaluate the hemodynamic responses and sedative effect of midazolam bolus following open heart surgery in children with congenital heart disease.Methods:All patients transferred from the operation room were put on ventilator.Invasive blood pressure and heart rate were closely monitored with SIEMENS 7000 monitor.Midazolam 0.1mg/kg intravenous bolus was administered when the child showed signs of recovering from anesthesia.The sedative effect was evaluated with Ramsay Sedation Score.Results:25 patients were included in this study.Midazolam intravenous injection showed excellent sedative effects in all patients with Ramsay score between 3 to 5 grade(P<0.001).Significant decrease in systolic blood pressure and diastolic blood pressure(P<0.001)were found 10 minutes after midazolam intravenous bolus.Hypotension occurred in 5 patients

and rapid infusion was needed to maintain blood pressure.The blood pressure began to rise in 15 minutes and restored to pre-medication level in 60 minutes.There was no significant change in heart rate after midazolam administration(P>0.5).Conclusions:Midazolam showed excellent sedative effect following open heart surgery.Midazolam intravenuos bolus

even in low dose

may cause significant blood pressure decrease.It is suggested that midazolam intravenous bolus be used with caution

especially in haemodynamic unstable state.