Cerebral blood flow, PaCO2 changes, and visual evoked potentials in mechanically ventilated, preterm infants

Area of Science:

• Neonatal Physiology
• Cerebrovascular Regulation
• Pediatric Critical Care

Background:

• Mechanically ventilated preterm infants (<33 weeks gestational age) often have altered cerebral blood flow (CBF).
• Understanding CBF regulation, particularly CO2 reactivity, is crucial for managing these vulnerable neonates.

Purpose of the Study:

• To estimate global cerebral blood flow (CBF) and assess CBF-CO2 reactivity in mechanically ventilated preterm infants.
• To investigate the relationship between CBF, arterial blood pressure, and visual evoked potentials (VEP).

Main Methods:

• Global CBF was measured twice using 133-Xenon clearance in 16 mechanically ventilated preterm infants.
• CBF-CO2 reactivity was assessed before and after ventilator setting changes or during spontaneous PaCO2 fluctuations.
• Visual evoked potentials (VEP) were recorded in some infants to correlate with CBF and arterial blood pressure.

Main Results:

• CBF-CO2 reactivity was found to be normal (+67%/kPa and +52%/kPa in the two groups) and significantly higher than interindividual estimates.
• No significant correlation was observed between CBF and arterial blood pressure.
• VEP showed no relationship with CBF levels or changes, even at low CBF values.

Conclusions:

• CBF-CO2 reactivity appears normal in clinically stable, mechanically ventilated preterm infants, indicating well-regulated cerebral circulation.
• The absence of a CBF-VEP relationship suggests that cerebral blood flow was not critically decreased in these infants.