Postnatal changes in intracranial blood flow velocity in preterm infants.

Postnatal changes in intracranial arterial blood flow velocity, were studied in preterm infants of less than 34 weeks of gestation. The blood flow velocity was measured in an artery on the base of the skull, using a range-gated Doppler ultrasound velocimeter. Ten healthy infants (mean gestational age 32.5 weeks), and ten infants with transitional respiratory disease (mean gestational age 31.3 weeks) were studied at 1, 2, 5, 24 h, and 2, 3, 5 and 10 days after birth. The healthy infants showed a consistent pattern of changes on the first day, with an average reduction in mean flow velocity of 29% between 1 and 5 h. At 24 h after birth, mean flow velocity had almost returned to the level of the 1 h recording. After 24 h there was a gradual increase in systolic and mean flow velocity until 10 days, while diastolic flow velocity remained unchanged. In the infants with respiratory disease there were no systematic changes in mean flow velocity on the first day, although large individual changes were seen. After 24 h no differences were seen between the healthy infants and the infants with respiratory disease. These findings indicate a transient decrease in cerebral perfusion during early circulatory transition in healthy preterm infants, and that mild to moderate respiratory disease causes larger individual variations in intracranial blood flow velocity.