The effect of a new branched chain--enriched amino acid solution on postoperative catabolism.

Branched-chain amino acids (BCAAs) may regulate muscle amino acid flux. Metabolic studies of both experimental animals and humans utilizing comparatively large amounts of BCAAs infused with hypocaloric glucose have shown that catabolism and proteolysis can be blunted. These studies suggested that the nitrogen-sparing properties of amino acid solutions used in postoperative trauma or sepsis might be improved by increasing the amount of BCAAs. This hypothesis was tested on ten patients undergoing operations of moderate severity utilizing a peripheral amino acid mixture with a branched-chain:non-branched-chain ratio of 45:55% given in 5% dextrose. The patients received 1.7 gm of protein equivalent/kg of ideal body weight in 5% dextrose-crystalloid solution with a concentration of 3.5% amino acids for the first 5 postoperative days. Nitrogen balance, 3-methylhistidine excretion, blood chemistries, and plasma amino acid profile tests were done daily. The results showed that nitrogen equilibrium was maintained for 5 postoperative days without any untoward effects on patients, their surgical wounds, or hepatic function. Plasma amino acids showed no significant changes from baseline with the exception of elevations of the BCAAs. We conclude that this 45% BCAA-enriched solution may be safely administered to patients with postoperative traumatic injury and results in nitrogen equilibrium over a 5-day period.