Muscle Catabolism and Outcomes in Children Following Cardiac Surgery

The central objective of our single center, pilot study in children with CHD following cardiac surgery is to identify serial changes in QMLT, as an estimate of LBM, during the first postoperative week, and to examine its relationship to functional status, assessed by FSS, after hospital discharge. Primary Aim 1. To measure the percent change in QMLT by mUS during the first postoperative week in children undergoing complex cardiac surgery. The investigators hypothesize children undergoing complex cardiac surgery will have a mean decline of at least 10% in QMLT during the first postoperative week. Primary Aim 2. To examine the relationship between percent change in QMLT during the first postoperative week and FSS at 3 and 6-months. The investigators hypothesize there is a direct relationship between percent change in QMLT during the first postoperative week and FSS at 3 and 6-months following surgery. Secondary Aim 1. To explore the relationship between nitrogen balance, defined as the difference between total nitrogen intake and total urinary nitrogen loss, and mean change in QMLT during the first postoperative week. The investigators hypothesize there is a direct correlation between nitrogen balance and mean change in QMLT during the first postoperative week in children following complex cardiac surgery. The proposed utilization of mUS to measure alterations in body composition during the acute phase of critical illness may provide early prediction of subsequent functional status decline.