Amino acid metabolism in parenteral nutrition: With special reference to the calorie: Nitrogen ratio and the blood urea nitrogen level

A clinical and experimental study was made on amino acid metabolism during parenteral nutrition with glucose and a synthetic amino acid solution. Good correlation was noted between the calorie: nitrogen ratio of the infusate and the blood urea nitrogen level, as well as between the calorie: nitrogen ratio and the amount of urinary excretion of urea nitrogen, nonprotein nitrogen, and amino nitrogen. Final results revealed that the extent to which amino acid is utilized for protein synthesis is directly proportional to the caloric supply, and for complete utilization of 1 g of nitrogen the required caloric intake is in the neighborhood of 450 total calories or 425 nonprotein calories. Blood urea nitrogen level can be used as a parameter of amino acid utilization during parenteral nutrition. Its level is influenced not only by renal function but also by calorie: nitrogen ratio of infusate.