Definition

Hypoxic ischemic encephalopathy (HIE) is a condition in which the brain does not receive enough oxygen. This particular condition refers to an oxygen deficiency to the brain as a whole, rather than a part of the brain. Although the term most often refers to injury sustained by newborns, HIE can be used to described any injury from low oxygen.

HIE can be fatal. Within as little as five minutes of oxygen deprivation, brain cells can begin dying. The disease can also cause long-term damage, including intellectual disability , delayed development, seizures , and cerebral palsy .

Blood Supply to the Brain

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Causes

There are a variety of causes of HIE. Any injury and many health conditions can potentially cause oxygen deprivation to the brain. Some common causes are:

• Injury or complication during birth
• Respiratory failure
• Blocked or ruptured blood vessel
• Carbon monoxide or cyanide poisoning
• Drug overdose
• Drowning
• Lack of oxygen due to smoke inhalation
• Extremely low blood pressure
• Strangulation
• Cardiac arrest
• Carbon monoxide poisoning
• High altitudes
• Choking
• Compression or injury to the trachea that reduces or stops breathing
• Complications from general anesthesia
• Diseases that cause paralysis of the respiratory organs or muscles (eg, myasthenia gravis, Guillain-Barre syndrome)

Risk Factors

Any injury, complication, or condition that causes the brain to have a reduction in blood flow and oxygen deprivation is a risk factor for HIE.

Symptoms

Symptoms include:

• Mild case:
  • Difficulty concentrating or paying attention
  • Poor judgment
  • Poor coordination
  • Euphoria
  • Extreme lethargy

• Severe oxygen deprivation:
  • Seizures
  • Coma
  • No brain stem reflexes (eg, breathing, responding to light)
  • Only blood pressure and heart function reflexes are functioning

Diagnosis

The doctor will work quickly to do a physical exam. Typically, the history is the most important factor in making the diagnosis.

Tests may include the following:

• CT scan—a scan that uses x-rays and computer software to make pictures of your brain
• MRI scan—a test that uses magnetic waves to make pictures of structures inside the brain
• Electrocardiogram (EKG, ECG)—a test that records the heart’s activity by measuring electrical currents through the heart muscle
• Echocardiogram—a test that uses high-frequency sound waves (ultrasound) to examine the size, shape, and motion of the heart
• Blood tests, including arterial blood gases and blood glucose levels
• Electroencephalogram (EEG)—a test that records the brain’s activity by measuring electrical currents through the brain
• Ultrasound—a test that uses sound waves to evaluate blood flow in the vessels going to the brain or within the brain
• Evoked potential test—neurophysiologic test that evaluates functioning of the brain by recording brain waves

Treatment

Treatment depends on the underlying cause of the condition, as well as the severity of the damage to the brain. Treatment options include:

• Life-sustaining treatment—If brain function has stopped but damage is not yet extensive, life-sustaining treatment is administered.
• Mechanical ventilation—This may be needed to sustain breathing.
• Treatments for the circulatory system—Treatments are administered to maintain heart function and control blood pressure.
• Seizure control—Medicine and general anesthesia may be administered to control seizures.
• Cooling—Hypoxic brain damage is often caused by heat. Cooling blankets or other means of cooling may be applied to reduce the body's temperature.
• Hyperbaric oxygen treatment—This treatment is used in cases of carbon monoxide poisoning.

Prevention

In most cases, HIE is unexpected and cannot be prevented. To prevent significant or long-term brain damage once the oxygen supply has been reduced, CPR may be administered.