What is the pathophysiology of hypoxic-ischemic encephalopathy (HIE)?

Updated: Jul 18, 2018
  • Author: Santina A Zanelli, MD; Chief Editor: Dharmendra J Nimavat, MD, FAAP  more...
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Answer

The initial compensatory adjustment to an asphyxial event is an increase in CBF due to hypoxia and hypercapnia. This is accompanied by a redistribution of cardiac output to essential organs, including the brain, heart, and adrenal glands. A blood pressure (BP) increase due to increased release of epinephrine further enhances this compensatory response. See the image below.

Fetal response to asphyxia illustrating the initia Fetal response to asphyxia illustrating the initial redistribution of blood flow to vital organs. With prolonged asphyxial insult and failure of compensatory mechanisms, cerebral blood flow falls, leading to ischemic brain injury.

In adults, CBF is maintained at a constant level despite a wide range in systemic BP. This phenomenon is known as the cerebral autoregulation, which helps maintain cerebral perfusion. The physiologic aspects of CBF autoregulation has been well studied in perinatal and adult experimental animals. In human adults, the BP range at which CBF is maintained is 60-100 mm Hg.


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