Blind randomized trial of a single bolus dose of dexmedetomine followed by a continuous infusion (CIVI) for up to 24 hours in infants who immediately post-operative from cardiac surgery and require tracheal intubation with mechanical ventilation in the post-operative period. Three bolus and infusion dose will be administered to a total of 36 patients.

This clinical trial of three dose rates of dexmedetomine will determine the pharmacokinetics of the drug in infants who remain tracheally intubated postoperatively. An exploratory pharmacodynamic study of a non-invasive device measuring sedation will be performed. Although the pharmacokinetics of dexmedetomine have been described for pediatric patients, the drug disposition in infants has not been well described. A range of doses has been studied, yet there are no reports describing the optimal dose for post-operative pediatric patients. This study will provide data that may allow for improved dosing recommendations in this critically ill population of children.

Inclusion Criteria:

• Greater than or equal to 1 month, less than or equal to 24 months
• Post-operative from cardiac surgery with tracheal intubation/mechanical ventilation in the immediate post-operative period
• Planned tracheal extubation within 24 hours post-operative period
• Renal function-serum creatine = 1.5 times the ULN for age
• Total bilirubin less than or equal to 1.5 X upper limit of normal (ULN) for age
• SGPT (ALT) ,less than+ 3x upper limit of normal (ULN) for age
• Signed written informed consent

Exclusion Criteria:

• Patients who have received another investigational drug within the past 30 days
• Receiving intermittent or continuous muscle relaxation during study period
• Patients who have a positive blood culture without a subsequent negative culture or other evidence of ongoing serious infection.
• Patients who in the opinion of the investigator may not be able to comply with the safety monitoring requirements of the study.
• Post-Operative hypotension
• Heart block
• Weight < 5 kg
• Patients who, in the opinion of the investigator, are not appropriate candidates for an investigational drug study.