Fluid, electrolyte, and glucose maintenance in the very low birth weight infant.

The low birth weight premature newborn, less than 1000 gm, represents a difficult problem in the management of parenteral fluid, electrolyte, and glucose maintenance. To assess this problem, six infants (mean weight 720 gm, range 575-835 gm; mean gestation 26.5 +/- 0.4 SEM wk) nursed under radiant warmers were evaluated during the first three days of life to determine volume of fluid intake, sodium and dextrose intakes, and urine output. Insensible water loss (IWL) was measured on a metabolic scale. In accordance with current recommendations, infant received fluid volumes of 111 +/- 10, 152 +/- 16, and 191 +/- 27 ml/kg/day on days 1, 2, and 3, respectively. Sodium intake (usually as 0.2% saline) ranges 0-8.5 mEq/kg/day. Dextrose infusions (as 10% solution) ran from 3.3 to 13.7 mg/kg/min. Insensible water loss measured 159 +/- 15 ml/kg/day. Despite increasing fluid intake, serum sodium concentration increased from 141 +/- 3 mEq/l on day 1 to 155 +/- 7 mEq/l on day 3 (p less than 0.05). None of the infants became oliguric and only two urine specimens had specific gravity greater than 1.015. These data demonstrate a larger insensible water loss than reported previously in small infants, but increasing the administration of standard 10% dextrose and 0.2% saline solution to balance insensible losses may result in sodium and glucose overload. Recommendations are made for adjusting parenteral fluid therapy for birth weight groups 600-800, 801-1000, 1001-1500, and 1501-2000 grams and for environmental conditions or radiant warmer or incubator, with or without plastic shielding or phototherapy.