 Study Design:The research design consists of a prospective study group that would be compared to two control groups a prospective control groups and a retrospective control group. The study group will consist of critically ill children receiving CRRT and IV carnitine supplementation added in the TPN. The prospective control group will consist of critically ill children not receiving CRRT or carnitine Retrospective control group will consist of critically ill children who received CRRT but did not receive carnitine supplementation. . Subjects for the prospective study and control groups will be recruited from the pediatric intensive care unit PICU and the cardiac intensive care unit CICU at Childrens National. Informed consent will be obtained from participants enrolled in the prospective study and control groups. Data for the retrospective control group will be obtained from the medical record. 