SEPARATION BY GEL FILTRATION AND MICRODETERMINATION OF UNBOUND BILIRUBIN

Summary Extraction of unbound bilirubin by Sephadex gel filtration and measurement by a micro‐method were carried out in 45 sera from jaundiced newborns (hemolytic disease or prematures). In about half the cases some free bilirubin with values in the range 0.1 to 1 mg/100 ml was detected. Levels above 0.5 mg/100 ml were exceptional (only 2 cases). Five autopsies were performed in prematures with unbound bilirubin levels above 0.1 mg/100 ml, and one kernicterus was found. Two infants with unbound bilirubin levels of more than 0.5 mg / 100 ml had clinical symptoms of kernicterus. No symptoms of kernicterus were observed in infants with high total bilirubin together with an insignificant amount of unbound bilirubin. The main interest of this method lies in the direct assessment of a toxic element originating from varying bilirubin and albumin levels and the micro‐environment of the bilirubin‐al‐bumin binding. But other factors, such as the cell membrane permeability and/or the duration of exposure, are likely to play a prominent role.