Ammonia metabolism in normal newborn infants and those with idiopathic hyperbilirubinemia

Normal newborn infants are shown to have a higher content of ammonia in the peripheral blood than their mothers, and the high levels persist for at least 10 days after birth. The level of ammonia in the blood of parturient women is normal. Infants with idiopathic hyperbilirubinemia have abnormally high levels of ammonia in the blood. Samples of blood from the umbilical vein near the entrance of the portal vein have higher concentrations of ammonia than are found in the infant's peripheral venous blood. Therefore, blood from the portal vein seems to contain elevated levels of ammonia in the newborn. The mechanism of this is not clear. The placenta appears to remove ammonia from the blood of the fetus. The high ammonia content of stored blood, and its possible effects on the infant in exchange transfusions were investigated and are discussed. A correlation between concentrations of unconjugated bilirubin and ammonia in the blood was not found in the newborn period.