• To measure how long ketamine remains in blood after a single dose of ketamine is given (venous) to children undergoing cardiac surgery on cardiopulmonary bypass (CPB)compared to levels of children undergoing cardiac surgery without CPB. [ Time Frame: Length of time ketamine remains in the blood ] [ Designated as safety issue: No ]
  

Drug: Ketamine

subject will then receive an intravenous bolus dose of ketamine 2 mg/kg as a rapid intravenous bolus, over less than two minutes just prior to CPB. In the non-CPB patients, ketamine will be administered just prior to the skin incision. All doses will be rounded to the nearest tenth of a milligram.

Timed blood samples will be collected at standardized times after the completion of the ketamine infusion and samples will be obtained from an indwelling arterial line. Each blood sample for pharmacokinetic analysis will be 1 mL.

The role of ketamine in pediatric anesthesia is well established. It is one of the most commonly used agents for conscious sedation in pediatrics. Its widespread use stems for its abrupt onset of action and brief duration of sedation. There is limited ketamine pharmacokinetic data in children and none to our knowledge in infants and young children who will be given an intravenous bolus dose before a surgical procedure that includes cardiopulmonary bypass. Ketamine is marketed as a racemic mixture (50:50 mixture of S- and R-ketamine enantiomers).

Ketamine undergoes N-demethylation (CYP3B6, 2C9, and 3A4) to its primary active metabolite,norketamine, with minor inactive metabolites, dehydroxynorketamine, generated secondary to direct oxidation. Ketamine exhibits a high intrinsic clearance with hepatic clearance dependent on hepatic blood flow under normal circumstances. One inherent disadvantage associated with the use of cardiopulmonary bypass (CPB) is the potential for organ dysfunction post-operatively. We propose an open-label controlled study describing the disposition of ketamine in 28 infants and children who will be undergoing cardiac surgery with (n=16) and without (n=12) CPB. We anticipate that cardiopulmonary bypass alters the pharmacokinetics of ketamine.