Regional cerebral blood velocity in infants. A real-time transcranial and fontanellar pulsed Doppler study.

To quantitate blood velocity while maintaining the real-time ultrasound image of the intracranial vessels in infants, we used a commercial phased-array pulsed Doppler scanner and developed a transcranial technique to measure the middle cerebral artery velocity, and a fontanellar approach to measure flow velocities in the basilar, internal carotid, anterior cerebral, and the pericallosal arteries. In 22 healthy term and 25 stable preterm infants, the peak spectral systolic velocities in the internal carotid and basilar arteries in term infants were 45 +/- 3.1, and 38.8 +/- 2.5 cm/sec, (mean +/- SEM), respectively. A hierarchical pattern of velocity variation was noted between the large and small intracranial vessels in both the term and preterm infants. The velocities were 30-40% higher in the proximal than in the smaller distal, anterior cerebral, and pericallosal arteries (P less than 0.05). Although the velocities in corresponding vessels were slightly lower in preterm infants than in the term, the differences were statistically not significant. In both groups, the end diastolic velocities did not change significantly among the large and small arteries; therefore, a significant variation in Pourcelot's index (PI, the ratio of maximum systolic-end diastolic difference to the systolic velocity) was noted between the internal carotid and the pericallosal arteries: 0.88 +/- 0.01 vs. 0.76 +/- 0.02, (P less than 0.05). A nearly parabolic velocity profile was documented in the vessels studied.