Plasma amino acid concentrations during branched-chain amino acid infusions in stressed patients.

To determine the effect of infusing large quantities of BCAA on plasma amino acid concentrations, plasma amino acid profiles were measured in 18 stressed patients before and 48 to 96 hours after initiation of amino acid solutions enriched with or exclusively containing BCAA (15.6+, 50%, 100%). Plasma concentrations of BCAA were elevated in the 100% and 50% BCAA groups, but not in the 15.6% group. Methionine, glycine, and phenylalanine concentrations were increased in the 15.6% BCAA group: methionine and glycine were decreased in the 100% BCAA groups. In the 50% BCAA group, nonbranched-chain amino acids maintained baseline concentrations. The 50% solution best preserved nitrogen balance of the BCAA solutions. The plasma amino acid profiles of patients with maple syrup urine disease (BCAA levels 5 to 10 times normal) were compared to our patients receiving BCAA-enriched solutions. Although plasma BCAA levels were elevated in our patients, allo-isoleucine, alanine, and glutamine concentrations were normal; the amino acid abnormalities of maple syrup urine disease were not observed.