Parenteral nutrient needs of very low birth weight infants

To determine nitrogen and mineral needs in parenterally nourished very low birth weight infants.

Prospective observational study.

Neonatal intensive care unit.

Twenty-four very low birth weight infants (< 1.2 kg) expected to receive parenteral nutrition (PN) exclusively for 3 weeks beginning 3 days after birth.

Infants received PN solutions according to nursery protocol. Serial 24-hour balance studies were conducted twice weekly. Clinical therapies were tabulated.

Intake, urinary excretion, and apparent retention of nitrogen, sodium, potassium, zinc, copper, calcium, phosphorus, and magnesium after initiation of PN.

Although urinary K, Zn, Ca, P, and Mg excretion (but not N, Na, and Cu excretion) increased after PN therapy was begun, net nutrient retention increased significantly above baseline for all nutrients. Average weekly nutrient retention was significantly below intrauterine estimates of nutrient accretion for N, Na, Ca, P, and Cu; closely approximated estimates for Zn; and significantly exceeded those for K and Mg. Regression analysis was used to predict parenteral nutrient intakes that would support postnatal nutrient retentions equivalent to the intrauterine estimates. Postnatal therapy with dexamethasone affected N, P, and K excretion and retention.

Soon after PN administration is begun, positive nutrient balance may be achieved early in the neonatal period. The magnitude of this effect remains uniform during PN administration. Adjustments in parenteral nutrient intake are needed to provide nutrient intakes sufficient to support postnatal retention at rates similar to those of intrauterine accretion. These data should be considered in the design of future studies to determine optimal PN needs of very low birth weight infants.