Role of insulin in the response to surgical stress during total parenteral nutrition

We investigated the hormonal response and the effects of exogenous insulin administration, in a group of glucose tolerant patients undergoing major abdominal surgery, during total parenteral nutrition, both before operation and during 2 days of uncomplicated post-operative course. In the fasting state, shortly after surgery, hyperglicemia (7.3 ± 0.6 vs 4.2 ± 0.3 mmol/l before surgery, mean ± SEM; p < 0.01), with normal level of insulin (73 ± 15 vs 54 ± 18 pmol/l; p = ns), a 18% increase in energy expenditure, and accelerated (+100%) protein oxidation, were associated with a rise in controregulatory hormone activity: cortisol (472 ± 31 vs 162 ± 19 ng/ml; p < 0.01), GH (3.1 ± 1.1 vs 0.4 ± 0.1 ng/ml; p < 0.05), prolactin (7.1 ± 1.2 vs 3.3 ± 0.4 ng/ml; p < 0.05), urinary catecholamines (0.17 ± 0.02 vs 0. 10 ± 0.01 μg/min; p < 0.01) and with a decrease in T3 (37 ± 4 vs 97 ± 7 ng/dl; p < 0.01) and testosterone levels (1.4 ± 0.4 vs 2.6 ± 0.7; p < 0.05). Serum cortisol concentrations bore a strong direct relation to the exogenous insulin infusion rate (r = 0.78; p < 0.001). TSH and T4 levels were unchanged. During 24 hours of total parenteral nutrition (15% protein, 55% glucose, and 30% fat), 8 times more insulin was needed after (14.4 ± 1.15 pmol · min-1 · Kg-1) than before surgery (1.78 ± 0.29 pmol · min-1 · Kg -1; p < 0.001) to clamp plasma glucose concentration at normal level. Insulin treatment, however, normalized net carbohydrate oxidation (18.8 ± 1.4 vs 17.2 ± 1.8 μmol · min-1 · kg-1 preoperatively; p = ns) and suppressed net lipid oxidation.