Substrate efficacy in early nutrition support of critically ill multiple trauma victims

The metabolic consequences of excessive nutrition support in patients have been increasingly recognized in recent years. Time-dependent optimal nutrition support is desired for an early and uncomplicated recovery after severe injury or illness. Metabolic effects of adding balanced amino acids to glucose infusion during total parenteral nutrition were investigated in 18 patients after major trauma (injury severity score 32 +/- 2). Two studies were conducted on each subject, one in the early "flow" phase of injury (40-60 hours postinjury) in the basal state without any dietary intake and then after 4 to 6 days of intravenous nutrition provided solely as glucose (24 +/- 2 kcal/kg per day, 80% resting energy expenditure, n = 8) or isocaloric glucose (28 +/- 3 kcal/kg per day) with amino acids (275 +/- 28 mg of nitrogen per kilogram per day, n = 10). Whole-body fuel substrate kinetics were studied for energy metabolism (indirect calorimetry), protein kinetics (primed-constant infusion of 15N glycine), and lipid mobilization (two-stage infusion of 10% glycerol). Injury-induced hypoaminoacidemia was equally modulated whether the glucose-based nutrition had amino acids or not. The negative nitrogen balance is reduced similarly in both groups. Protein breakdown rate is significantly (p = .025) decreased in both groups and it is more so (30% vs 18%) in patients receiving total parenteral nutrition. Intravenous nutrition could not stimulate protein synthesis. Whole-body lipolysis rate as well as net fat oxidation rate are suppressed more when glucose alone is given, and this also results in less reesterification. Provision of intravenous glucose alone, not to exceed the resting energy expenditure, seems to be superior to isocaloric glucose with amino acids during this early catabolic flow phase of injury because the injured body could not assimilate this exogenous amino acid.