Transformation of bilirubin in gastrointestinal tract and its relationship to neonatal icterus.

The object of the study was the transformation of bilirubin in the neonatal digestive tract with special reference to enterohepatic circulation of nonconjugated bilirubin and its consequences. The application of biochemical and chromatographic methods showed that bilirubin excreted by neonatal livers was qualitatively distinct from that excreted by adult livers. Already in the first meconium practically all bilirubin conjugated with glucuronic acid was hydrolyzed, which means ample availability of nonconjugated bilirubin for its reresorption by intestines. The enterohepatic circulation of nonconjugated bilirubin could indirectly be demonstrated by early elimination of nonconjugated bilirubin reservoir - meconium - from the digestive tract. This resulted in a significant reduction of bilirubinaemia. It could be shown that in newborns with hyperbilirubinaemia alterations of structure of bilirubin excreted into bile due to phototherapy occurred. This finding leads to an assumption that besides a favourable effect, apparently predominating in bilirubin degradation, phototherapy tends in an undesirable way to increase enteral reabsorption of nonconjugated bilirubin back in the circulation.

Phototherapy: the cause of increased enterohepatic circulation of bilirubin in newborn infants?

The unconjugated/conjugated bilirubin ratio which was examined in the feces of 17 newborn infants submitted to phototherapy, was approximately 1:1 before, during and after the treatment. These results are not in keeping with those of Lund and Jacobsen who demonstrated an increased concentration of unconjugated bilirubin in duodenal bile. From this discrepancy one can deduce the unfavorable hypothesis that phototherapy stimulates the intestinal reabsorption of unconjugated bilirubin to the circulation.

Hyperbilirubinemia connected with parenteral administration of higher amounts of fluids in premature infants.

During a study on the influence of different amounts of fluid intake on water and electrolyte metabolism in the first 3 days of life, a high incidence of hyperbilirubinemia was observed in infants receiving a large water load (150 ml/kg/24 h) intravenously. The amount of meconium excreted during the 3-day period in newborns with total parenteral alimentation was significantly lower than in controls. Hyperbilirubinemia is considered to be due to the enterohepatic circulation of bilirubin present in the retained meconium. The role of slight hemolysis and insufficient stimulation of choleresis is discussed.

[Fat-emulsions and acid-base balance in neonates of low weight at birth (author's transl)]. / Fettemulsionen und Säure-Basen-Gleichgewicht bei Neugeborenen mit niedrigem Geburtsgewicht

The influence of a single intravenous infusion of triglycerides (1 g triglyceride per kg body weight) on the acid base equilibrium was investigated in 16 newborn infants with low birth weight during the first days of age. No changes of pH, PCO2 and standard bicarbonate, base excess, buffer base and actuelle bicarbonate, respectively, were observed. Fat emulsions can be used, therefore, without hazards in the parenteral feeding of newborn infants.