Renal function during the first 72 hours of life in sick infants with birthweight less than 1250 grams.

Renal function was evaluated by inulin clearance (Cin) in infants weighing less than 1250 g (N = 16) during the first 72 hours of life. Their mean +/- SD gestational age (GA) was 28.5 +/- 2.2 weeks and the birthweight (BW) was 990 +/- 158 g. Eleven studies were performed on day 1, 9 on day 2, and 11 on day 3. Mean Cin were 0.27 +/- 0.23, 0.37 +/- 0.13, and 0.46 +/- 0.44 mL/kg/min on days 1, 2, and 3, respectively, but the changes were not significant. Individual Cin values ranged from 0.039 to 1.54 mL/kg/min. The Cin was lower than that observed in larger and more mature infants. There was no correlation between Cin and fractional sodium excretion (FeNa), GA, BW, or fluid intake. Fe Na did not correlate with serum sodium or sodium intake.