PRELIMINARY DATA Intestinal Barrier Function in Children after Cardiopulmonary Bypass. In a single center pilot study, Dr. Typpo evaluated serial plasma biomarkers of intestinal EBF (plasma claudin 3, citrulline, I-FABP, and regulatory cytokines) in 20 children with CHD over 5 days, before and after CPB. Dr. Typpo found that intestinal EBF improved with early EN, was associated with symptoms of feeding intolerance (Pilot congenital cardiac feeding intolerance scale-pCCFIS) (p<0.05) and with characteristics of cardiopulmonary support. The current proposal will expand on this pilot data to identify key clinical variables which alter intestinal EBF biomarker profiles across 3 centers, leveraging existing practice variation for vasoactive infusion titration, and EN delivery. While investigators have demonstrated that our pilot CC-FIS correlated with biomarkers of intestinal EBF at a single center, study personnel will now validate this score across three centers and between a variety of providers.