Amino acid utilization during total parenteral nutrition in the surgical neonate

Abstract

Amino acids, urea nitrogen, and creatinine in plasma and urine, and total urinary nitrogen were determined in five neonates during prolonged parenteral feeding. A fibrin hydrolysate-dextrose or a crystalline amino acid-dextrose solution was infused for periods as long as 33 days. These solutions supplied essential amino acids and total nitrogen (mostly as glycine) in excess of that available to infants on oral diets. Despite weight gain, positive nitrogen balance, and the absence of excessive amino aciduria, several biochemical abnormalities were detected. Plasma lysine, leucine, and glycine were consistently elevated and in one low birth weight infant, plasma phenylalanine and valine were also markedly raised. The excessive supply of glycine and nitrogen resulted in elevated urea levels in the blood and urine. The capacity to transform phenylalanine to tyrosine and methionine to cystine required by infants fed the tyrosine-cystine-free crystalline amino acid solution may be deficient in low birth weight premature infants and others with impaired liver function. These findings suggest that a more precise tailoring of the amino acid content of infusates for parenteral feeding is indicated. Such individually tailored solutions would decrease the metabolic and excretory load on the liver and kidneys.