Free amino acid levels in the blood of patients undergoing parenteral alimentation

Arterial and venous plasma and whole blood amino acid levels were analyzed in 103 samples from 25 patients on parenteral feeding. In spite of disparity in the variables (patient problems, type and duration of alimentation), a significant correlation was found for most amino acids with the rate of infusion. During infusion, levels increased for alanine, valine, glycine, isoleucine, leucine, proline, threonine, serine, methionine, phenylalanine and lysine. The branched-chain amino acids were negatively correlated with the rate of glucose infusion; only alanine was positively correlated. There was no arteriovenous change across the forearm for any amino acid or glucose infusion rate, even though amino acid levels were in some instances 3 to 5 times normal; this may imply that the initial processing of amino acids occurs in other tissues.