Parenteral amino acid supplementation with high-dose insulin prevents hypoaminoacidemia during cardiac surgery.

OBJECTIVES: Surgery triggers a stress response that produces insulin resistance and hyperglycemia. During cardiac surgery, the administration of high-dose insulin along with dextrose titration maintains normoglycemia, but dramatically decreases plasma amino acids (AAs) compared with preoperative fasting levels. Hypoaminoacidemia limits protein synthesis and prevents anabolic responses after surgery. We investigated whether parenteral infusion of AAs during and immediately after cardiac surgery would prevent hypoaminoacidemia in patients who receive high-dose insulin therapy. METHODS: Sixteen patients undergoing coronary artery bypass grafting surgery were randomly allocated to receive AAs with % kcal equivalent to either 20% (n = 8) or 35% (n = 8) of their measured resting energy expenditure (REE). Insulin was infused at a constant rate of 5 mU/(kg × min), whereas dextrose was titrated to maintain normoglycemia during and until 5 h after surgery. Plasma AA concentrations were measured at baseline before and after surgery. RESULTS: Compared with the 20% AA group after surgery, AA concentrations were significantly higher in the 35% AA group for 12 of 20 AAs (P < 0.032), including all branched-chain AAs. In the 20% AA group, total essential AAs decreased by 21% and nonessential AAs decreased by 14% after surgery compared with preoperative fasting levels. In contrast, giving 35% AAs prevented this unfavorable decrease in AAs, and in fact allowed for a 23% and 12% increase in essential and nonessential AAs, respectively. CONCLUSIONS: AA supplementation at 35% REE, but not 20% REE, can effectively prevent hypoaminoacidemia caused by high-dose insulin therapy during cardiac surgery.

Hyperinsulinemic-normoglycemic clamp administered together with amino acids induces anabolism after cardiac surgery.

Cardiac surgery triggers an inflammatory stress response, leading to protein catabolism, a process that even high-dose insulin therapy alone cannot reverse. To determine whether hyperinsulinemic-normoglycemic clamp and perioperative amino acid (AA) supplementation improves whole body protein balance, 20 patients scheduled for elective coronary artery bypass grafting surgery were randomly assigned to have intra- and postoperative hyperinsulinemic-normoglycemic clamp, with or without intravenous AA supplementation. Primed continuous infusions of [6,6-2H2]glucose and l-[1-13C]leucine were used to quantify whole body protein and glucose metabolism before and after surgery. Adipose tissue and serum cytokines were also analyzed to measure their responsiveness to the anabolic effect of AA administration. During hyperinsulinemic-normoglycemic clamp, AA supplementation successfully stimulated whole body protein synthesis, resulting in a positive whole body protein balance after surgery (insulin: -13.6 ± 4.5 vs. insulin + AA: 2.1 ± 5.4 µmol·kg-1·h-1, P < 0.001). Endogenous glucose production was equally suppressed in both groups (insulin: 0.0 ± 3.8 vs. insulin + AA 1.6 ± 1.6 µmol·kg-1·min-1, P = 0.230). AA supplementation led to significant changes in serum and tissue IL-6 (insulin: 246.6 ± 111.2 vs. insulin + AA: 124.5 ± 79.3 pg/ml, P = 0.011). In conclusion, hyperinsulinemic-normoglycemic clamp technique, together with AA supplementation, can induce an anabolic state after open-heart surgery, as quantified by a positive whole body protein balance.