Accelerated splanchnic amino acid uptake after cardiac surgery

Energy expenditure increases after cardiac surgery, but changes in peripheral tissue metabolism do not explain this increase. We hypothesized that the splanchnic region is a major contributor to the postoperative hypermetabolism, and this should be reflected in the exchange of amino acids across the splanchnic bed. We measured systemic and regional (splanchnic and leg) amino acid exchange, oxygen uptake and hemodynamics in 22 elective coronary bypass grafting patients postoperatively after arrival to the intensive care unit, 2 h later, and after stabilization of hemodynamics. Splanchnic uptake of glutamine (50 +/- 37 micromol/min/m2 to 78 +/- 37 micromol/min/m2, P < 0.05) and three of the gluconeogenetic amino acids, alanine (115 +/- 52 micromol/min/m2 to 183 +/- 70 micromol/min/m2, P < 0.05), serine (18 +/- 10 micromol/min/m2 to 26 +/- 13 micromol/min/m2) and threonine (20 +/- 8 micromol/min/m2 to 28 +/- 8 micromol/min/m2) increased during the observation period. Similarly, the oxygen consumption by the splanchnic region increased while splanchnic blood flow remained stable. A correlation between oxygen and amino acid uptake by the splanchnic bed was observed during the study period. Femoral exchange of glutamine and alanine did not change, although femoral blood flow and oxygen consumption increased during rewarming. High metabolic activity was observed in the splanchnic region during the early postoperative phase after hypothermic cardiac surgery. The increased plasma amino acid concentration indicates a release of amino acids from other sources than the peripheral muscle.