Twenty-four hour hyperinsulinemic-euglycemic clamp improves postoperative nitrogen balance only in low insulin sensitivity patients following cardiac surgery

Background Critically ill patients often suffer from a protein catabolic state. The aim of this study was to demonstrate that nitrogen balance (NB) in cardiac patients admitted to the intensive care unit (ICU) is related to their insulin sensitivity level and that supraphysiologic doses of insulin can restore anabolism. Materials and methods Twenty-eight patients that were admitted to ICU in enteral and/or parenteral nutrition have been enrolled in this study. All patients received a standard nutrition protocol for at least 3 days before starting the study. These patients received either enteral or parenteral nutrition based on 1.4 kcal/kg/h and 1.1 g/kg/24 h of proteins. Participants were studied for three 24 h periods (P1, P2, and P3). Twenty-four hour NB was calculated from urinary urea nitrogen excretion, fixed protein and energy intake during each of the three periods (P1, P2, and P3). Simultaneous to P2, a 24 h hyperinsulinemic-euglycemic clamp (HEC) was performed to determine patients' insulin sensitivity (IS) or insulin resistance (IR), as well as the impact of high doses of insulin on NB. Results Nitrogen balance remained consistently positive in the IS group regardless of the clamp. In IR patients, NB was negative before the clamp and became positive during P2 and P3. Insulin sensitivity improved during the HEC in IR patients (P < 0.001). Conclusions A negative NB was found only in insulin resistant patients admitted to the ICU for more than 7 days. A 24-h period HEC improved NB in these patients.