Objective: Currently blood urea nitrogen (BUN) is commonly used as a marker of protein intolerance in very preterm infants. The purpose of this study was to evaluate the relationship between amino-acid intakes and BUN concentrations during the early neonatal period in preterm neonates.
Study design: Retrospective review of BUN concentration data from 121 infants with birthweight <or=1250 g receiving exclusive parenteral nutrition over the first 72 hours of life.
Results: There were 136 separate BUN concentration values. Amino-acid intake range was 0 to 3.7 g kg-1 day-1 and nonprotein calorie intake range was 15 to 45 kcal kg-1 d-1. There was no correlation between BUN concentration and amino-acid intake (p=0.2 and r2=0.01).
Conclusions: In parenterally nourished preterm neonates amino-acid intake is not correlated with BUN concentration in the first days of life. Therefore, limiting amino-acid intake based on BUN concentration is not warranted in this patient population.