Intravenous lipid and bilirubin-albumin binding variables in premature infants

Abstract

Background: The lipid intake at which a significant bilirubin-displacing effect occurs as a function of gestational age (GA) is unclear.

Objective: To determine the effect of gradual increase in IL intake from 1.5 to 3 g/kg per day on bilirubin-albumin binding variables as a function of GA in premature infants with indirect hyperbilirubinemia.

Methods: Infants of 24 to 33 weeks' gestation at birth who received IL (20% Intralipid [Fresenius Kabi, Uppsala, Sweden]) doses of 1.5, 2, 2.5, and 3 g/kg per day over 4 consecutive days were prospectively evaluated. The blood samples were drawn twice at least 8 hours apart on each IL intake to measure total serum bilirubin and free bilirubin by the peroxidase test. The highest free bilirubin on each IL intake, the corresponding total serum bilirubin, and serum albumin were used to calculate the bilirubin/albumin binding constant or binding affinity.

Results: Sixty-two infants (median GA: 28 weeks) were studied during the first 10 days of life. None of the subjects had culture-proven sepsis, had triglyceride levels of >2.05 mmol/L, or were receiving steroids. Infants were grouped in 2-week GA intervals. The cumulative frequency of elevated free bilirubin concentration (>or=90th percentile or B(f) >or= 32 nmol/L) as a function of IL intake was inversely related to GA and was significantly different among 2-week GA groups. There was significant decrease in binding affinity and increase in free bilirubin concentration with higher IL intake for <or=28 week but not for >28 week GA groups.

Conclusions: The IL intake may be associated with a significant fall in the binding affinity of bilirubin for plasma protein and a concomitant increase in free bilirubin concentration in premature infants. The lipid intake at which this occurs depends on GA.

FIGURE 1

B_f (nmol/L) (A), binding affinity or constant K (L/μmol) (B), and TSB concentration (μmol/L) (C) as a function of IL intake and GA (n = 62). Analyses were performed using 2-way repeated measure analysis of variance. The symbols “a” and “b” on top of the lines signify the significance of the test comparing GA groups at each level of IL intake (^a P < .05; ^b P < .01). The Δ on the right signifies the significance of the test comparing the IL dosages within the GA group; P < .01.