Whole-body protein kinetics in elective surgical patients receiving peptide or amino acid solutions.

We compared the efficacy of two enteral solutions that were isonitrogenous and of identical amino acid composition but differed in that one solution contained only free amino acids whereas the other contained a mixture of free amino acids and peptides. Protein kinetics and nitrogen balance were evaluated in a group of six elective surgical patients. Primed-constant infusion with 15N-glycine was started 24h after gynecologic surgery and sustained over 3 days. During the first postoperative day, patients received enteral 0.45% saline. During postoperative days two and three, the patients received either the free amino acid solution or the mixture of peptides and free amino acids in a crossover design. There were no differences in protein kinetics or nitrogen balance with the two treatments.