Sedation With Dexmedetomidine During Cardiac Catheterization

Clinical dose escalation drug trial to evaluate the effect of 3 different doses of dexmedetomidine on the pulmonary vascular bed in pediatric subjects with elevated pulmonary vascular resistance. The study will be conducted in 2 parts, with a pilot phase incorporating stopping rules to optimize safety of the drug in this population. Study subjects will include pediatric subjects with Pulmonary Hypertension (PHTN). Part 1: This will be the dose escalation phase of the study. Twenty four evaluable subjects will be enrolled. Subjects will include pediatric subjects with pulmonary hypertension (PVR\>4WU) undergoing hemodynamic cardiac catheterization and vasoreactivity drug testing. Cohorts of 8 evaluable subjects will receive dose level 1, dose level 2, or dose level 3 of Dexmedetomidine (DEX). The dose will be escalated to the next dose of DEX once all subjects have been enrolled in the preceding DEX dose cohort, and safety has been established at that level. Inadequate sedation despite the highest dose of DEX at each level will be considered a treatment failure on an intention to treat basis. Part 2: This part of the study will be conducted after the pilot phase is safely completed, and the full complement of subjects will be recruited.