Bilirubin binding and acid-base equilibrium in newborn infants with low birthweight.

Acidosis is known as a risk factor for the development of bilirubin encephalopathy in neonatal jaundice. However, few attempts have been made to evaluate the influence of acid-base state on bilirubin-albumin binding state in blood of newborn infants. Therefore, in 171 appropriate and 83 small for gestational age newborns (birthweight less than 2,500 g) the acid-base state in blood and bilirubin (BR) binding state in serum was measured at the ages of 3, 4, 5, and 8 days. There is a weak but significant correlation between standard base deficit and the ratio BR/reserve albumin as well as the toxic potential of serum BR. The results suggest that the higher risk in acidosis is not only caused by increased tissue binding of BR but also--at least partially--attributable to decreased BR binding in serum.