Simultaneous Measurement of Velocity Curves: Carotid Artery and Middle Cerebral Artery in Neonates.

We measured simultaneously the flow velocity curves of the common carotid artery and the middle cerebral artery to evaluate the relationship between the systemic and cerebral circulations in the early neonatal period. Eligible for inclusion in this study were 20 healthy full-term neonates. Doppler ultrasound examinations were performed at 1, 2, 3, and 4 days after birth. The flow velocity curves of both arteries were recorded using a multi-channel Doppler system. Systolic maximal velocities and end-diastolic velocities were measured, and resistance indices (RIs) were calculated. The flow velocity of the middle cerebral artery increased during the first three days after birth, but that of the common carotid artery did not change. The RI of the middle cerebral artery remained constant, but that of the common carotid artery decreased on the third day after birth. These data suggest that the cerebral arteries might work as resistance vessels.