Accelerated nitrogen loss after traumatic injury is not attenuated by achievement of energy balance

Background: We wanted to determine if achievement of energy balance decreases myofibrillar protein catabolism and nitrogen loss during posttraumatic catabolic illness. Methods: Surgical intensive care unit of a level I trauma center in a university medical center. Trauma patients expected to be mechanically ventilated for at least 4 days were randomly assigned to one of three parenteral feeding groups: (1) nonprotein calorie group: dextrose and intake equal to measured energy expenditure; (2) total calorie group: dextrose, lipid, and protein intake equal to measured energy expenditure; and (3) hypocaloric group: dextrose and lipid intake equal to 50% of measured energy expenditure. Target protein intake for all groups was 1.7 g/kg body wt. On day 4 of nutrition support, a 24-hour balance study was conducted. Urine urea and total nitrogen production, 3-methylhistidine excretion, energy expenditure, and substrate utilization were measured. Results: Despite significant differences in nonprotein and total calorie balance among the groups, nitrogen loss, nitrogen balance, and catabolic rate were not significantly different. Nitrogen loss correlated with catabolic rate but not with energy expenditure or energy balance. Catabolic rate was associated with energy expenditure but not with energy balance. Nitrogen loss was positively correlated with the percentage of nonprotein energy expenditure met by nonprotein calorie intake. Conclusions: Achievement of energy balance (nonprotein or total energy) failed to decrease catabolic rate or nitrogen loss acutely in multiple trauma patients. Provision of caloric intake equal to energy expenditure does not seem necessary during the acute phase of posttraumatic catabolic illness.