Parenteral nutrition and protein sparing after surgery: do we need glucose?

Although capable of inducing an anabolic state after surgery, parenteral nutrition, including glucose, leads to hyperglycemia. Even moderate increases in blood glucose are associated with poor surgical outcome. We examined the hypothesis that amino acids, in the absence of glucose supply, spare protein while preventing hyperglycemia. In this prospective study, 14 patients with colonic cancer were randomly assigned to undergo a 6-hour stable isotope infusion study (3 hours of fasting followed by 3-hour infusions of amino acids, Travasol [Baxter, Montreal, Canada] 10% at 0.02 mL · kg−1 · min−1, with or without glucose at 4 mg · kg−1 · min−1) on the second day after colorectal surgery. Protein breakdown, protein oxidation, protein balance, and glucose production were assessed by stable isotope tracer kinetics using l-[1-13C]leucine and [6,6-2H2]glucose. Circulating concentrations of glucose, cortisol, insulin, and glucagon were determined. The administration of amino acids increased protein balance from −16 ± 4 μmol · kg−1 · h−1 in the fasted state to 16 ± 3 μmol · kg−1 · h−1. Combined infusion of amino acids and glucose increased protein balance from −17 ± 7 to 7 ± 5 μmol · kg−1 · h−1. The increase in protein balance during nutrition was comparable in the 2 groups (P = .07). Combined administration of amino acids and glucose decreased endogenous glucose production (P = .001) and stimulated insulin secretion (P = .001) to a greater extent than the administration of amino acids alone. Hyperglycemia (blood glucose, 10.1 ± 1.9 μmol/L) occurred only in the presence of glucose infusion. In summary, excluding glucose from a short-term feeding protocol does not diminish the protein-sparing effect of amino acids and avoids hyperglycemia.