Blood Urea Nitrogen During the First 2 Weeks of Life in Vlbw Infants Receiving High Protein Intakes

Abstract

Objective: High protein intakes have been associated with elevated blood urea nitrogen (BUN). This study evaluated BUN values in VLBW infants receiving high protein intakes postnataly according to recent recommendations. Methods: BUN were evaluated in 102 infant with a birth weight < 1250g during the first 2 weeks of life. Analyses were evaluated during 3 periods of 5 days. Protein intake was 2.4±0.3, 3.8±0.6 and 4.0±0.6 g/kg*d on the first day, after 1 week and after 2 weeks respectively. Results: 102 infants were included (BW=1005±157g, GA=25.5±1.9wks). Simple correlation analyses demonstrated that BUN decreased with protein intakes (r=-0.16,p< 0.01), postnatal age (r=-0.21,p< 0.01) and enteral feeding progression (r=-0.40,p< 0.01); and BUN increased with blood creatinine values (r=0.71,p< 0.01) and postnatal weight loss (r=0.33,p< 0.01). Similar correlations were observed during the 3 periods. Multivariate analysis demonstrated that the major independent factor influencing BUN was blood creatinine value, explaining ∽50% of the value. Protein intakes explained ∽1% of urea value during the first 2 weeks of life. Conclusions: BUN may not be interpreted in term of protein tolerance during the first 2 weeks of life in VLBW infants. BUN was mainly determined by renal function during early postnatal period.