Blood flow and metabolism in the developing brain

Abstract

The newborn brain has mechanisms that act to preserve the blood flow to the brain stem. When challenged with an asphyxial episode, there is a redistribution of blood flow in the brain. The brain stem structures have increased blood flow, and telencephalic structures, particularly white matter, have decreased flow. These changes are made possible in part because the newborn brain stem vascular appears to be much more sensitive to pCO2 than the telencephalic vasculature. In fact, several brain stem regions exhibit a higher sensitivity to CO2 than the adult cortex. Consequently, vessels in this region are able to vasodilate more effectively. In addition, the sympathetic vascular innervation in the newborn brain appears more profuse in the forebrain. So this system could produce a widespread vasoconstruction and participate in the shift of blood flow from the cerebral hemispheres to the brain stem. This capacity to preserve blood flow to the critical brain stem regions may explain, in part, the ability of the neonatal animal to survive long periods of asphyxia. This phenomena might also explain the clinical findings of white matter loss and stroke in the cerebral hemispheres, since these regions seem to be selectively deprived of blood flow during insult. This relationship is summarized in Fig 1.