Blood urea nitrogen and serum bicarbonate in extremely low birth weight infants receiving higher protein intake in the first week after birth

Objective: To determine correlation between early protein administration and serum blood urea nitrogen (BUN) or bicarbonate (HCO3-) in extremely low birth weight (ELBW) infants during the first week of life. Study Design: A retrospective review of 154 ELBWs was conducted. Laboratory and nutritional data from postnatal days 1, 4 and 7 were collected. Repeated measures models estimated the relationship of protein intake with BUN and HCO3- in the first week of life. Result: In total, 359 separate BUN and HCO3- values were analyzed. Each gram per kilogram of protein administered was associated with an increase in mean BUN of 3.3 mg/dl. This effect decreased daily by 2.1 mg/dl. Each gram per kilogram of protein administered was associated with a decrease in mean HCO3- by 0.9 mmol/l. Conclusion: The association between protein load and BUN is positive but decreasing over time. Protein is associated with a clinically insignificant decrease in HCO3-. Concerns regarding metabolic derangement from early protein administration in ELBWs are unwarranted. Journal of Perinatology (2011) 31, 535-539; doi:10.1038/jp.2010.204; published online 10 February 2011