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What is hypoxia? Hypoxia is the state in which an organ has a reduced supply of oxygen.

What is hypoxic-ischemic encephalopathy (HIE)?

HIE is the injury to brain tissue that results from a severe reduction in oxygen supply, without total deprivation. HIE is most commonly associated with intrapartum asphyxia of neonates, but may occur at any age. HIE in adults is usually caused by cardiac arrest, but may be the consequence of other causes of decreased oxygen supply, such as hanging, strangulation, and near-drowning.

How is the severity of HIE classified?

In infants, HIE can have lasting consequences and is classified based on severity to help predict the level of future disability. The most common scoring tool used is the Sarnat scale:

1. Mild HIE– Usually associated with no neurodevelopmental deficits. The infant is alert with normal muscle tone, increased deep tendon reflexes, and exaggerated primitive reflexes. Autonomic abnormalities may include jitteriness, tachycardia, and mydriasis. Seizures are absent.

2. Moderate HIE– The infant is lethargic with mild hypotonia, increased or decreased deep tendon reflexes, and weak primitive reflexes. Autonomic abnormalities may include bradycardia and miosis. Seizures are common.

3. Severe HIE– May result in permanent disability or death. The infant is unresponsive to physical stimuli with flaccid muscle tone, decreased or absent deep tendon reflexes, and absent primitive reflexes. Autonomic functioning is usually severely impaired and varies by individual. Seizures are frequent and may be hard to control.

Source: Armstrong-Wells, J. (2021, October 15). Hypoxic-ischemic Encephalopathy Stages and Symptoms. Cancer Therapy Advisor. Retrieved June 30, 2022, from