Serum creatinine in very low birth weight infants during their first days of life

Little is known about the relationship between gestational age (GA) or birth weight (BW) and serum creatinine (SCr) in very low birth weight (VLBW) infants. We sought to study postnatal SCr changes and determine if there is a correlation between GA or BW and SCr in VLBW infants, during their first days of life.

Medical records of all VLBW infants, who were admitted to our neonatal intensive care unit (NICU) between 1 May 1998 and 1 May 2001, were reviewed. Medical records were reviewed for: BW, GA, gender, race, APGAR scores, mechanical ventilation, use of medications, fluid intake, urinary output, protein intake, blood urea nitrogen (BUN) and SCr during the first days of life. Patients with anuria/oliguria, major congenital anomalies, low APGAR scores at 5 min, on high ventilator settings (on the oscillator), hemodynamically unstable (on pressors, inotropes) and on indomethacin and diuretics were excluded.

In total, 138 infants met our inclusion criteria. SCr was found to decrease postnatally, reaching a plateau on day 5 of life in all VLBW infants (repeated measure analysis of variance; P=0.004); however, there was a delay in the decrease of SCr in the subgroup of infants <29 weeks GA, and <1000 g BW. SCr (on day 5 of life) was also found to decrease with increasing GA and BW (Pearson correlation coefficient: -0.206 (P=0.05) and -0.236 (P=0.05) respectively).

In VLBW infants SCr decreases significantly during the first days of life; however, in infants younger than 29 weeks GA or smaller than 1000 g BW there is a delay in the decrease of their SCr that extends beyond the first days of life. We also conclude that during the first days of life, and in VLBW infants SCr decreases with advancing GA and BW.