Plasma ionised calcium in preterm infants: comparison with adults.

Plasma calcium (ionised and total) and albumin concentrations and pH were measured in preterm infants and in healthy adults and patients dependent on respirators. Plasma ionised calcium and total calcium values fell during the first week after birth and subsequently rose. Plasma ionised calcium concentrations in preterm infants were higher than those found in both healthy and sick adults. This difference was only partially explained by the lower blood pH in the infant population. There was no correlation between plasma ionised calcium or the ratio of ionised calcium to total calcium and total bilirubin concentrations. These results suggest that the metabolic control of plasma ionised calcium in preterm infants is different from that in adults.