Postnatal serum concentrations of endogenous free fatty acids in newborns admitted to the neonatal intensive care unit: effects on unbound bilirubin

Abstract

Background: Few studies have reported the characterization of postnatal serum concentrations of endogenous free fatty acids (FFAs) in high-risk newborns and their effects on unbound bilirubin (UB). Methods: Serum concentrations of FFA, albumin (Alb), UB and total bilirubin (TB) were measured in 713 samples obtained within 5 days after birth from 439 newborns without intravenous lipid supplementation admitted to the neonatal intensive care unit (NICU). Serum FFA was reported as the day-specific percentile-based curve. Serum FFA and FFA/Alb ratios were compared in term and preterm patients. To assess the impact of FFA on UB, daily changes in FFA/Alb and UB/TB ratios were compared in term patients without receiving phototherapy or any drugs, and linear regression analysis was performed between FFA/Alb ratio and serum UB concentration or UB/TB ratio using 140 sera with hyperbilirubinemia of term and preterm patients. Results: A percentile-based curve showed that serum FFA peaked at 1 day of age and progressively decreased. Serum FFA and the FFA/Alb ratio were significantly higher in term than in preterm patients at birth and 1 and 3 days of age. FFA/ Alb ratio significantly changed over 5 days after birth, but UB/TB ratio remained constant. FFA/Alb ratio did not correlate with serum UB concentration or UB/TB ratio in sera with hyperbilirubinemia. Conclusions: We assessed postnatal concentrations of serum FFA in a large number of high-risk newborns admitted to the NICU. The concentration of endogenous FFAs in newborns admitted to the NICU was not rising until it influenced UB.

Disorders of bilirubin binding to albumin and bilirubin-induced neurologic dysfunction

“…Serum FFAs can be increased by exogenous lipid emulsions as well as by stress. However, we recently assessed postnatal FFA concentrations and the FFA:albumin molar ratio in a large number of sick newborns who were admitted to our neonatal intensive care unit (NICU), and found that all of the patients had an FFA:albumin molar ratio <4 [18]. Because endogenous serum FFA concentrations do not affect UB concentrations, pediatricians should be aware of the potential displacing effects of FFAs in extremely preterm infants receiving >1.5 g/kg/day of exogenous, intravenous lipid supplementation [17].…”

Plasma Free Fatty Acids and their Binding Proteins in Preterm Infants

“…Many authors have indicated that disturbances in the serum free FAs (FFA) concentration in preterm infants could be significantly related with short-term and long-term morbidities [1][2][3]. Deposition of lipids in a fetus increases exponentially with gestational age, reaching a rate of accretion of around 7 g/day just before labor [4].…”