Abnormal Doppler velocimetry and blood flow volume in the middle cerebral artery in very severe intrauterine growth restriction: is the occurence of reversal of compensatory flow too late?

Cerebral Blood Flow Monitoring in High-Risk Fetal and Neonatal Populations

Cerebrovascular pressure autoregulation promotes stable cerebral blood flow (CBF) across a range of arterial blood pressures. Cerebral autoregulation (CA) is a developmental process that reaches maturity around term gestation and can be monitored prenatally with both Doppler ultrasound and magnetic resonance imaging (MRI) techniques. Postnatally, there are key advantages and limitations to assessing CA with Doppler ultrasound, MRI, and near-infrared spectroscopy. Here we review these CBF monitoring techniques as well as their application to both fetal and neonatal populations at risk of perturbations in CBF. Specifically, we discuss CBF monitoring in fetuses with intrauterine growth restriction, anemia, congenital heart disease, neonates born preterm and those with hypoxic-ischemic encephalopathy. We conclude the review with insights into the future directions in this field with an emphasis on collaborative science and precision medicine approaches.

Cerebral blood flow dynamic in foetuses with hypoplastic left heart syndrome: Incremental value of the first segment of the anterior cerebral artery over the middle cerebral artery?

OBJECTIVE

To investigate the blood flow Doppler parameters of the anterior cerebral artery (ACA) in foetuses with hypoplastic left heart syndrome (HLHS).

METHODS

Doppler parameters (peak systolic velocity [PSV], end-diastolic velocity [EDV], time-averaged maximum velocity [TAMXV] and pulsatility index [PI]) and biometric parameters were measured in two anatomical segments of the ACA (S1 and S2) and in the middle cerebral artery (MCA) in 35 HLHS foetuses and 73 gestational age-matched normal foetuses. Correlations between the cerebral artery PIs and head circumference (HC) were assessed.

RESULTS

Both EDV and TAMXV of the ACA and MCA in the HLHS group were significantly higher than in the normal group (P < .05). The PI of the ACA and MCA in the HLHS group were significantly lower than in the normal group (P < .05). ACAS1PI and ACAS2PI in the HLHS foetuses with retrograde blood flow in the aortic isthmus (AoI) were significantly lower than those of HLHS foetuses without retrograde blood flow in the AoI (P < .05). ACAS2PI was significantly lower than ACAS1PI in the HLHS foetuses with retrograde blood flow in the AoI (P = .047). The abnormal rates of ACAS1 and ACAS2 were significantly higher than that of the MCA (P < .05) in the HLHS group. The HC and biparietal diameter were significantly lower in the HLHS group than in the control group (P < .05). HC was correlated with the PIs of ACAS1, ACAS2 and the MCA in the HLHS group (P < .05).

CONCLUSION

A redistribution of foetal cerebral blood flow appeared in HLHS, and the measurement of ACA PI might provide early information on brain hypoxia.

Brain-Sparing in Intrauterine Growth Restriction: Considerations for the Neonatologist

Intrauterine growth restriction (IUGR) is most commonly caused by placental insufficiency, in response to which the fetus adapts its circulation to preserve oxygen and nutrient supply to the brain ('brain-sparing'). Currently, little is known about the postnatal course and consequences of this antenatal adaptation of the cerebral circulation. The altered cerebral haemodynamics may persist after birth, which would imply a different approach with regard to cerebral monitoring and clinical management of IUGR preterm neonates than their appropriately grown peers. Few studies are available with regard to this topic, and the small body of evidence shows controversy. This review discusses the cerebral circulatory adaptations of IUGR fetuses and appraises the available literature on their postnatal cerebral circulation with potential clinical consequences.