Intravenous nitrogen intake requirements in full-term newborns undergoing surgery

To determine the intravenous intake of nitrogen needed to duplicate the weight gain and nitrogen retention observed in healthy infants fed human milk, full-term infants had weight change and nitrogen balance measured postoperatively while they were receiving two different parenteral regimens which provided adequate energy (87 kcal/kg/d) and varying intakes of nitrogen as crystalline amino acids (290 to 579 mg/kg/d) over a six-day period. Weight change was similar to that observed in breast-fed infants (35 g/d) and was independent of nitrogen intake. A significant correlation was observed between nitrogen intake and retention (r = .71, P less than .01). Substituting the rate of nitrogen retention observed in thriving full-term infants fed human milk into the regression equation describing the relationship between nitrogen intake and retention, the nitrogen intake required by parenterally fed infants in order to duplicate the accretion rate of their milk-fed counterparts was 280 mg/kg/d. After correcting for individual variation, recommended intravenous amino acid intakes range from 2.3 to 2.7 g/kg/d depending on the commercial amino acid formulation chosen and providing that adequate amounts of energy are concurrently infused.