Related Experiment Videos
Cerebral blood flow and energy metabolism in the newborn
1Department of Neonatology, Rigshospitalet, Copenhagen, Denmark.
Insights
Cerebral blood flow (CBF) in newborns shows reserve capacity, with normal CO2 reactivity and autoregulation present even in preterm infants. However, severe asphyxia or intracranial hemorrhage can impair these functions.
Area of Science:
- Neonatal physiology
- Neurocritical care
Background:
- Newborn infants have lower cerebral blood flow (CBF) and oxygen metabolism than adults, but possess significant reserve capacity.
- Cerebral blood flow (CBF) reactivity to carbon dioxide (CO2) and pressure-flow autoregulation are crucial for maintaining brain homeostasis.
- Impaired autoregulation and CO2 reactivity are linked to adverse outcomes like intracranial hemorrhage in preterm infants.
Purpose of the Study:
- To review the current understanding of cerebral blood flow (CBF) regulation in newborns.
- To discuss the methods used to assess CBF and brain metabolism in neonates.
- To highlight the clinical significance of CBF dynamics in neonatal brain health.
Main Methods:
- Review of existing literature on neonatal cerebral blood flow (CBF) and brain metabolism.
- Discussion of various imaging and monitoring techniques, including Doppler ultrasound, magnetic resonance spectroscopy, and near-infrared spectroscopy.
- Analysis of studies examining CBF reactivity to CO2 and pressure-flow autoregulation.
Main Results:
- Normal term and preterm infants exhibit low CBF with high oxygen extraction, indicating reserve capacity.
- Evidence supports the presence of pressure-flow autoregulation and normal CO2 reactivity in preterm infants.
- Absence of autoregulation and CO2 reactivity is observed in infants with severe asphyxia or those developing intracranial hemorrhage.
Conclusions:
- Newborns possess physiological mechanisms to maintain adequate cerebral perfusion.
- Monitoring CBF and its reactivity is vital for identifying infants at risk of brain injury.
- Advanced techniques like near-infrared spectroscopy show promise for continuous monitoring of neonatal cerebral circulation.
Abstract:
In normal newborn term and preterm infants CBF is relatively low corresponding to a low metabolic rate for oxygen, whereas cross-brain oxygen extraction is similar to that in adults. This provides for a considerable reserve capacity to deal with decreased CBF or decreased oxygen content in arterial blood. CBF reactivity to CO2 is normal, and the evidence is that pressure-flow autoregulation is present, even in very preterm infants. Absence of autoregulation and CBF-CO2 reactivity has been documented in severely asphyxiated infants, and in preterm infants who went on the develop severe intracranial hemorrhage. A number of methods are available to study CBF and brain metabolism in newborn infants. Several of them involve ionizing radiation, which has limited their use, even though it is unlikely that the associated risks are particularly high. Magnetic resonance spectroscopy has demonstrated a delayed disturbance of energy metabolism following severe asphyxia. Doppler ultrasound has rarely been helpful to obtain quantitative data. Near infrared spectrocopy has now been in use for more than 10 years. It has been slow to fulfill its promise as a continuous monitor of cerebral circulation and of oxygen sufficiency of neurons.