Aberrations in Carnitine Homeostasis in Congenital Heart Disease With Increased Pulmonary Blood Flow

Overview

Infants with congenital heart disease and increased pulmonary blood flow have altered carnitine homeostasis that is associated with clinical outcomes; and L-carnitine treatment will attenuate these alterations and improve clinical outcomes. The investigators will pilot a trial assessing the safety and pharmacokinetics of perioperative IV L-carnitine administration in these patients. To this end, a pilot clinical trial is proposed. Infants with ventricular septal defects or atrioventricular septal defects undergoing complete surgical repair will receive L-carnitine (25, 50, or 100 mg/kg, IV) just prior to cardiopulmonary bypass (CPB) and 2hr after CPB. Carnitine levels will be measured before CPB, and before and 0.5, 1.5, 3, 5, 9, 12, and 24h after the second dose. The safety, pharmacokinetic profile, feasibility, and effect of L-carnitine administration on biochemical parameters, as well as clinical outcomes will be determined. The investigators expect this pilot to provide the data needed to proceed with a placebo-based randomized, controlled, trial.

AIM: To pilot a trial assessing the safety and pharmacokinetics (PK) of perioperative IV L-carnitine administration in these patients. To this end, a pilot clinical trial is proposed. Infants with VSD or AVSD undergoing complete repair will receive L-carnitine, in one of 3 doses (25, 50, or 100 mg/kg, IV), just prior to CPB, and again 2 hr after CPB. Serial blood samples will be obtained to determine free, total, and acylcarnitine levels, and plasma markers of mitochondrial function, oxidative stress, and bioavailable NO. Adverse events will be sought, and clinical outcomes will be assessed. Study design: The inclusion and exclusion criteria are as described in Aim 3A except only infants with VSD or AVSD will be enrolled (no TOF). The safety profile of L-carnitine is outstanding, with no reports of toxicity from overdose reported113. In fact, the only adverse reactions reported are transient nausea and vomiting, and less commonly gastritis. However, although rare, seizures have been reported to occur in patients receiving L-carnitine. Therefore, the major adverse events that will be monitored include evidence of seizure activity and GI bleeding. As per routine, any patient suspected of having seizures is monitored with continuous EEG. Dosing is not well studied in children, particularly critically ill children67, 114-116117. In addition, the effect of CPB on L-carnitine clearance in children is not known. Therefore, a major goal of this sub-aim is to establish a pharmacokinetic profile of L-carnitine in this patient population undergoing surgery with CPB, in order to move forward with a larger randomized trial powered for efficacy in prevention of increased PVR post-bypass in at-risk infants. Plasma concentration profiles after IV bolus dosing in adults were described by a two-compartmental model67, 113, 114, 118. Usual pediatric dosing is not well delineated, but recommendations include a 50 mg/kg bolus followed by an infusion of 50mg/kg/day, that can be increased to 300 mg/kg/day113, 119. Therefore, we will begin at a lower dose (25 mg/kg), and escalate the dose after each group of 5. No intra-patient escalation will be allowed and the dose will not be escalated until all patients in the current dose level have been followed to hospital discharge or 30 days post-op and the safety and PK data have been analyzed. The DSMB will approve all dose escalations. The dosing goal will be to achieve normal or supra-normal free carnitine levels (\~50 μmol/L) and low AC levels (\~3 μmol/L) just before and for 24 hrs after CPB; the period with the greatest risk of pulmonary vascular morbidity.