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THE EFFECT OF BRANCHED CHAIN AMINO ACIDS (BCCA) ON POSTOPERATIVE MUSCLE PROTEIN SYNTHESIS AND NITROGEN BALANCE F. Hammarqvist, J. Wernerman, A. von der Decken, E. Vinnars (Department of Anaesthesia and Metabolic Research Laboratory, S:t Erik's Hospital, Wenner-Gren Institute for Experimental Biology, Stockholm, Sweden)

BCAA are metabolized in skeletal muscle. It has been suggested that BCAA can stimulate protein synthesis. In this study a BCAA enriched amino acid solution was compared to a conventional one during total parenteral nutrition (TPN). The effects on muscle protein Synthesis and nitrogen balance following surgery were evaluated.

Methods: Patients undergoing cholecystectomy received postoperative TPN containing 0.18 g N/kg/d and 135 kJ/kg/d, equal energy amounts of carbohydrates and fat. The TPN of one group (n=6) was enriched in BCAA (BCAA 35%). The other group (n=9) received a balanced conventional amino acid mixture (VaminR, BCAA 12%). Percutaneous muscle biopsies were taken before surgery and on the third postoperative day. Nitrogen excretion was measured in 24-hour portions. Protein synthesis was determined by the concentration of ribosomes per mg DNA and by the percentage content of polyribosomes.

Results: The concentration of total ribosomes per mg of DNA decreased by 20% and the percentage content of polyribosomes by 25% on the third postoperative day. The concentration of polyribosomes per mg of DNA decreased by 40% on the third day following surgery. The nitrogen balance was negative throughout the study. No differences were observed between the two groups , one receiving the BCAA enriched, the other the conventional amino acid solution.

Conclusion: A BCAA enriched amino acid solution was given together with adequate amounts of nitrogen and calories and compared to a conventional TPN program. No benefits attributable to the BCAA enriched nutrition regarding muscle protein synthesis and nitrogen balance were seen.

DOES BRANCHED CHAIN AMINO ACID ENRICHMENT REDUCE MORTALITY IN SEPTIC AND TRAUMATIZE0 PATIENTS. C.L.H. van Berlo, M.F. von Meyenfeldt, M. Rouflart, P.B. Soeters (Department of Surgery, University of Limburg, Maastricht, The Netherlands). Branched chain amino acids (BCAA) have been associated with a nitrogen sparing effect in patients with trauma or sepsis. Nitrogen sparing would presumably result in enhanced protein synthesis and reduced protein degradation. Recent studies suggested that a 45% BCAA solution was the most appropriately BCAA enriched solution in an injured rat model, and that a minimum of 0.5 g BCAA nitrogen/kg body weight was necessary to obtain posi- tive nitrogen (N) balance. We therefore studied the effect of BCAA enrichment of stan- dard TPN-solutions in septic and traumatized patients on nitrogen balance and mortality. One hundred-one patients, 56 men and 45 women, were randomly selected to receive during 7 days either a standard (C) TPN solution, containing 15.6% BCAA or a BCAA enriched (BC) TPN solution, containing 50.2% BCAA. Patients were not allowed to receive any other nutritional support. The amount of non-protein energy (NPE) administered was calculated using the Harris-Benedict equation, with appropriate additions for specific dynamic activity of food, activity and stress. Nitrogen balances were calculated with correc- tions for changes in plasma urea pool. Mortality was assessed as not sepsis or stress related, early septic (within the 7-day study period) or late septic (after the 7 day study period). Fifty-two patients (28 o, 24 9) received the C solution, 49 (28 d', 21 9) the BC-sol. Mean age did not differ among groups. The NPE Cal/N ratio was 160 in both groups; C group patients received 0.17 g BCAA N/kg BW, BC-group patients received 0.56 g BCAA N/kg BW. Nitrogen balances were not different between groups: + - 3 g N/day. Nitrogen balan- ces closely reflected the estimated stress percentage. Patients with the lowest stress percentage were in positive N-balance, whereas high stress percentages were associated with more negative N-balances, again with no difference between BC and C groups. Morta- lity whether sepsis related or not was not different between groups: 34.7% BC, 30.8% C. We therefore were not able to confirm the reputed beneficial effects of BCAA enriched TPN solutions in septic and traumatized patients.

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