Nitrogen balance in extremely low birth weight infants with nonoliguric hyperkalemia.

We measured nitrogen balance and urinary 3-methylhistidine molar ratios in 33 extremely low birth weight infants (12 with hyperkalemia and 21 without) for the first 3 days of life. Although all infants were in negative nitrogen balance during the study, there was no difference in the degree of negative nitrogen balance between the two groups. There was also no difference in the 3-methylhistidine/creatinine molar ratios, indicating that muscle protein catabolism did not differ. We conclude that it is unlikely that catabolism contributes to the development of nonoliguric hyperkalemia in extremely low birth weight infants.

Whole-body protein turnover and nitrogen balance in young children at intakes of protein and energy in the region of maintenance

Nitrogen balance and whole-body protein turnover were measured in children aged about one year taking diets which provided 1.7 or 0.7 g milk protein/kg/d at three levels of metabolizable energy, 80, 90 and 100 kcal/kg/d. All the children were in positive nitrogen balance at all levels of energy intake on 1.7 g protein/ kg/d. Nitrogen equilibrium was maintained on 0.7 g protein/kg/d when the energy intake exceeded 90 kcal/kg/d, but on 80 kcal/kg/d nitrogen balance was negative. Whole-body protein turnover was measured from the enrichment in urinary ammonia following a continuous infusion of15N-glycine. The variation between individuals on the same diet was significantly greater than the variation within individuals at different levels of energy intake. For the group as a whole protein synthesis on 1.7 g protein/kg/d was 0.74, 0.75 and 0.87 g N/kg/d on 100, 90 and 80 kcal/kg/d respectively;whereas on 0.7 g protein/kg/d it was 0.37, 0.38 and 0.40 g N/kg/d. These results show that over this range of intakes protein synthesis decreased as dietary protein fell, but tended to increase as energy intake fell. (AU)

Human milk feeding in premature infants: protein, fat, and carbohydrate balances in the first two weeks of life.

The nutritional adequacy of the premature infant's own mother's milk was assessed during the first two weeks of life. Studies were carried out in three groups (n = 8) of infants of less than 1,300 gm birth weight, matched for gestational age and weight, and fed either pooled breast milk, their mothers own milk, or infant formula (SMA20 or SMA24). Macronutrient balances at the end of the first and second postnatal weeks demonstrated differences in nitrogen and lipid absorption and retention between groups. Nitrogen retentions (mg/kg/day) were similar to normal fetal accretion rates only in the PT and SMA24 groups. Fat absorption was poorest from the heat-sterilized PBM (average of 64.0% of intake) when compared to PT (88.2%) and SMA groups (83.3%). Average gross and metabolizable energy intakes were similar among groups. Nutritional status as measured by plasma total protein and albumin concentrations and weight gain tended to be poorest in the PBM-fed infants. It was concluded that either PT milk or infant formula of a composition similar to SMA24 are more appropriate than pooled banked milk for feeding the premature infant during the first two weeks of life.