Neonatal cerebral Doppler flow velocity waveforms in the uncomplicated pre-term infant: reference values

Area of Science:

• Neonatal physiology
• Cerebrovascular regulation
• Pediatric neurology

Background:

• Cerebral blood flow regulation is critical in preterm infants.
• Doppler ultrasonography is used to assess cerebrovascular status.
• Resistance index (RI) reflects vascular resistance in cerebral arteries.

Purpose of the Study:

• To evaluate the changes in cerebral artery resistance index (RI) in the first 10 days of life in preterm infants.
• To compare RI trends based on gestational age subgroups.
• To establish reference ranges for middle cerebral artery (MCA) and anterior cerebral artery (ACA) RI in healthy neonates.

Main Methods:

• Longitudinal study of 217 preterm infants (< 37 weeks gestation).
• Doppler flow velocity waveforms and resistance index (RI) calculated for MCA and ACA.
• Reference group (n=137) comprised non-acidotic infants with normal cerebral ultrasounds.

Main Results:

• Median RI for ACA and MCA significantly decreased within the first 12 hours of life in all gestational subgroups.
• Infants ≥ 33 weeks gestation showed stabilization of RI after 12 hours.
• Infants ≤ 32 weeks gestation exhibited a further RI decrease between 12-24 hours, followed by stabilization.
• Initially, RI was higher in the ≤ 32 weeks group, but no significant differences were observed later.

Conclusions:

• Cerebral artery resistance index (RI) demonstrates significant dynamic changes in the early neonatal period for preterm infants.
• The rate of RI stabilization differs based on gestational age, with earlier maturation observed in infants ≥ 33 weeks.
• These findings provide insights into the cerebrovascular adaptation of preterm infants and may inform clinical monitoring.