Renal Response in Low-Birth-Weight Neonates

Abstract
• Changes in renal function and extracellular fluid volume during the first ten days of life were studied in two groups of low-birth-weight neonates receiving different fluid and sodium intakes from the third to the tenth day. Group 1 neonates received less fluid and sodium and fewer calories than group 2 neonates. Renal function and inulin space were measured before (day 2) and after (day 8) the neonates received the different fluid and sodium managements. Group 2 neonates (on the eighth day) had less weight loss, lower plasma sodium and osmolal concentrations, and a similar inulin space per kilogram of body weight as on day 2. Group 1 neonates had more weight loss and a smaller inulin space on day 8 compared with day 2. Low-birth-weight neonates receiving high fluid and sodium loads from days 2 through 8 did not have a contraction of extracellular fluid volume as did those receiving lower fluid and sodium intakes during this period; as a result, the former group had a dilutional decrease in the plasma sodium level and osmolality. (Am J Dis Child1983;137:215-219)