THE EFFECT OF SLOW LIPID INFUSION AND DOSAGE ON BILIRUBIN BINDING TO ALBUMIN IN THE PREMATURE INFANT

Abstract

The effect of 15-hour lipid infusions at doses of 1, 2, and 3 g/kg, administered on successive days, on unbound bilirubin and the serum free fatty acid:albumin molar ratio (F/A) was studied in 20 AGA premature infants (BW mean ± SEM - 1.43 kg ± 0.09; EGA 30.7 wks ± 0.63) with physiologic hyperbilirubinemia (7.7 mg/dl ± 0.30). Albumin-bound bilirubin (B), reserve bilirubin binding capacity (R), and total unconjugated bilirubin were measured fluorometrically pre-infusion and 15-45 minutes before end-infusion. Serum free fatty acid levels were determined pre- and at end-infusion. Serum albumin was measured on day 1. The ratio B/R was used to estimate unbound bilirubin (Wells et al, Clin Chem 28:432,1982).Infants <30 wks gest. demonstrated a significant (p<.05) rise in the F/A ratio with each increase in lipid dose while infants ≥30 wks did not. The concentration of unbound bilirubin (B/R) increased linearly with increasing F/A ratio (r=.65,p<.001). The largest increases in B/R were seen in infants with F/A> 4.0; the EGA of these infants (28.7 wks ± .47) was significantly less (p<.01) than those infants whose F/A ratio was<4.0 (31.1 wks ± .40). In 10/58 infusions there was a fall in unbound bilirubin unrelated to BW, EGA or postnatal age. In all such instances, the end-infusion F/A was≤3.0.No significant increase in unbound bilirubin was seen in any infant receiving 1 g/kg fat emulsion despite increases in F/A. At doses of 2 and 3 g/kg increases in F/A in the infants < 30 wks resulted in increased unbound bilirubin. Monitoring of the F/A ratio may identify infants at risk for increased unbound bilirubin during lipid infusion. (Supported by NIH Grant RR-00240)