Postnatal adaptation of brain circulation in preterm infants

Area of Science:

• Neonatal physiology
• Cerebrovascular regulation
• Neuroprotection in preterm infants

Background:

• Preterm infants experience significant physiological changes post-birth.
• Cerebral circulatory dynamics are crucial for brain development and injury prevention.
• Understanding early circulatory changes can inform interventions for preterm neonates.

Purpose of the Study:

• To investigate global and regional postnatal cerebral circulatory changes in stable preterm infants.
• To assess the relationship between these circulatory changes and the presence of brain injury.
• To determine if early cerebral circulatory adaptations are influenced by physiological parameters or brain injury.

Main Methods:

• Near-infrared spectroscopy was used to measure cerebral blood flow (CBF) and cerebral blood volume (CBV).
• Color Doppler flow imaging assessed cerebral blood flow velocity and resistance index in major cerebral arteries.
• Serial cerebral ultrasound monitored for brain parenchymal echogenicity and intraventricular hemorrhage (IVH).

Main Results:

• CBF and cerebral blood flow velocity significantly increased over the first two days of life, irrespective of mean blood pressure, blood gases, hematocrit, or glycemia.
• Cerebral blood volume (CBV) and resistance index (RI) remained stable.
• No significant differences in CBF or velocity changes were observed between infants with or without brain lesions/IVH, but infants with IVH showed higher CBV on day two.

Conclusions:

• Early postnatal cerebral circulation in preterm infants demonstrates an intrinsic adaptation, coupling cerebral blood flow with metabolic demands independent of systemic blood pressure.
• Improved venous return, rather than vasodilation, may play a key role in this adaptation.
• While early CBF and velocity changes are not directly correlated with injury, elevated CBV in the presence of IVH suggests altered cerebral hemodynamics in injured brains.