No specific regimen has been universally accepted as ideal for sedation during cardiac catheterization in infants and children. We evaluated a combination of ketamine and dexmedetomidine for sedation during cardiac catheterization in children with congenital heart disease. The study design included a retrospective analysis of data sheets and hospital records. The protocol for sedation was standardized and data collected prospectively for an ongoing quality assurance project. Heart rate, blood pressure, and oxygen saturation were recorded every 1 minute for the first 5 minutes and then at 5-minute intervals. The efficacy of sedation was judged by the need for supplemental ketamine doses. The study cohort included 16 infants and children undergoing either diagnostic or therapeutic cardiac catheterization. Sedation was initiated with a bolus dose of ketamine (2 mg/kg) and dexmedetomidine (1 microg/kg) administered over 3 minutes followed by a continuous infusion of dexmedetomidine (2 microg/kg per hour for the initial 30 minutes followed by 1 microg/kg per hour for the duration of the case). Supplemental analgesia/sedation was provided by ketamine (1 mg/kg) as needed. The baseline heart rate was 103 +/- 21 beats/minute. After the bolus dose of ketamine and dexmedetomidine, the heart rate increased by 7 +/- 5 beats/minute. The greatest increase was 15 beats/minute. The low heart rate after the bolus dose of ketamine/dexmedetomidine or during the subsequent dexmedetomidine infusion was 91 +/- 20 beats/minute (P < 0.001 compared with baseline) and the high heart rate was 110 +/- 25 beats/minute (P < 0.01 compared with baseline). In two patients, the dexmedetomidine infusion was decreased from 2 to 1 microg/kg per hour at 12 to 15 minutes instead of 30 minutes as a result of a decreased heart rate. No clinically significant changes in blood pressure or respiratory rate were noted. Two patients developed upper airway obstruction, which responded to repositioning of the airway. No apnea was noted. During the procedure, the PaCO2 varied from 37.5 to 48 mm Hg and was > or =45 mm Hg in seven patients. No patient responded to local infiltration of the groin and placement of the arterial and venous cannulae. Three patients required a supplemental dose of ketamine (1 mg/kg) during the procedure. In two of these patients, this was required before changing the cannulae. Our preliminary data suggest that a combination of ketamine and dexmedetomidine provides effective sedation for cardiac catheterization in infants and children without significant effects on cardiovascular or ventilatory function.