NITROGEN-BALANCE, 3-METHYLHISTIDINE EXCRETION, AND PLASMA AMINO-ACID PROFILE IN INFANTS AFTER CARDIAC OPERATIONS FOR CONGENITAL HEART-DEFECTS - THE EFFECT OF EARLY NUTRITIONAL SUPPORT

Objective: The objective of this study was to evaluate the effect of n utritional support on proteolysis and plasma amino acid profile in inf ants early after cardiac operations for congenital heart defects. Meth ods: Thirty-seven patients, 2 to 12 months old, were randomized on pos toperative day 1 for 24-hour isocaloric metabolic study. Group STANDAR D (18 patients) received glucose as the maintenance fluid, and group P N (19 patients) received glucose and crystalloid amino acid solution a t a dosage of 0.8 +/- 0.1 gm/kg per day. The nonprotein caloric intake in the two groups was 25 +/- 15 and 33 +/- 9 kcal/kg, respectively (p = not significant). Results: The nitrogen balance was markedly less n egative in group PN than in group STANDARD (-114 +/- 81 vs -244 +/- 86 mg/kg, respectively, p = 0.001). There was a highly significant inver se correlation between the nitrogen balance and urinary 3-methylhistid ine excretion in both groups, but the muscle proteolysis was blunted m ore effectively in patients receiving amino acids. Concentrations of t he plasmatic branched-chain amino acids, alanine, glycine, and proline , decreased significantly in group STANDARD but not in group PN on pos toperative day 2. Glutamine and threonine levels declined significantl y on postoperative day 2 in both groups. Low levels of arginine were o bserved in our patients before operation and in the early postoperativ e period. The amino acid concentrations normalized on postoperative da y 7 in all patients. Conclusion: Significant proteolysis and hypoamino acidemia were observed in infants early after cardiac operations. This hypercatabolic response was blunted by parenteral nutritional support .