The sick very low birthweight infant fed by parenteral nutrition: studies of nitrogen and energy.

Nine ventilator-dependent intravenously-fed very low birthweight infants with a mean birthweight of 938 (range 760-1100)g and mean gestation of 27 (range 25-29) weeks were studied provided they continued to receive more than 85 per cent of their nutritional needs intravenously. Metabolic balance studies of nitrogen over 72h were undertaken between 2 and 45d postnatal age. The average number of balances performed on each infant was three. The balances were performed at a mean postconceptional age of 5, 15, 25 and 37d. The data were compared to postconceptional age-matched fetal values and to published data from well enterally-fed infants at equivalent postnatal ages and matched for postconceptional age. There was a steady increase in length, weight and head circumference throughout the study period. The mean (range) nitrogen retention was 340 (229-415) mg/kg/d and was similar to intrauterine accretion after 200d postconceptional age, and comparable to nitrogen retention rates seen in well and enterally-fed premature infants. We conclude that parenteral nutrition can sustain growth and support nitrogen retention in the small preterm infant requiring intensive care.