A study of the plasma free amino acids in infants of low birth weight, with a comparison of oral feeding with milk and total parenteral nutrition.

The plasma amino acid concentrations soon after birth, at 10 days and 1 month, were estimated in 25 infants of low birth weight (less than 1 500 g). Ten of these infants were fed with amino acids as casein hydrolysate, through the umbilical artery for the first 10 days. The normal range of plasma amino acid values for infants of low birth weight shows a wider range of concentrations than that of term infants. During total parenteral nutrition (TPN) the plasma amino acid values were generally elevated above those obtained in infants receiving conventional feeding with a "humanised" milk formula. In particular, the concentrations of aspartic acid, phenylalanine, cystine, leucine, isoleucine and glutamic acid were significantly higher. With the cessation of TPN, these levels returned to normal, so that no significant difference could be detected between the 2 groups after 1 month. The suitability of current amino acid solutions for paediatric use is discussed.