Early curbing of protein hypercatabolism in postoperative patients by nutritional support with glucose plus amino acids, but not with glucose alone

This work attempts to determine if there are differences in protein metabolism in post-surgical patients who receive parenteral nutrition with amino acids plus glucose (G+AA) or conventional gluco-salinal solution (GS). Eighteen patients submitted to gastrointestinal surgery were randomized and double-blindly administered either G+AA (1 g AA/kg.d and 28 kJ/kg.d), or GS (28 kJ/kg.d). Protein metabolism was determined 12 h after surgery (day 0) and after 5 days of nutritional support. On day 0, protein breakdown was simillarly elevated, with respect to reference values, in both groups (GS: 4.62 ± 0.25; G+AA: 5.25 ± 0.50 g prot/kg.d) as a result of surgical stress. These values increased significantly at day 5 (P < 0.03) with the administration of GS to 6.93 ± 1.00 g prot/kg.d, while they decreased (P < 0.002, 3.30 ± 0.42 g prot/kg.d) with G+AA. Protein synthesis was increased (5.69 ± 0.86 g prot/kg.d) with GS (P < 0.02), and was decreased (2.79 ± 0.44 g prot/kg.d) with G+AA (P < 0.0002). Both synthesis and breakdown were inside normal reference values after 5 days for group G+AA. In both groups, nitrogen balance did not change significantly at day 5 compared to day 0. G+AA is effective in curbing the hypermetabolism produced by postoperative stress, achieving normal protein metabolism in 5 days, while GS increases the protein breakdown and synthesis. Nitrogen balance does not detect these modifications of the protein metabolism. Undernutrition on prognosis is not yet fully recognized.