Hypoxic Ischemic Encephalopathy

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What is hypoxic ischemic encephalopathy?

Hypoxic ischemic encephalopathy (HIE) is an umbrella term for a brain injury that happens before, during, or shortly after birth when oxygen or blood flow to the brain is reduced or stopped.

While some children who experience HIE at birth may not have any long-term consequences, others can experience mild to severe disabilities or even death. The severity of HIE-related issues depends on many factors, including:

  • How long the brain is without oxygen or blood flow
  • How much of the brain is affected
  • How the individual’s brain repairs itself

Encephalopathy, or a decrease in blood flow or oxygen to the brain, can affect many different organs, not just the brain. Individuals with HIE may have heart, lung, kidney, or liver problems.

Immediately during or after the brain injury, the infant or child may have the following symptoms:

  • Low heart rate
  • Breathing problems
  • Too much acid in body fluids (acidosis)
  • Seizures or unusual movements
  • Stained meconium (a newborn’s first stool)
  • Low muscle tone
  • Blue or very pale skin
  • Low reflexes

Individuals with HIE may be diagnosed with perinatal encephalopathy, perinatal asphyxia, neonatal encephalopathy, or birth asphyxia. Health problems that result from HIE typically occur in two stages: when the brain is initially deprived of oxygen and blood, and when normal blood flow returns and toxins are dispersed from the damaged cells (this is called reperfusion injury and usually occurs six to 48 hours after the initial trauma).  

Brain injuries from HIE can cause:

  • Developmental delays
  • Intellectual disabilities
  • Epilepsy
  • Cerebral palsy
  • Heart problems or cardiac arrest

The extent of the damage in HIE may not be understood for several months or years after the brain injury occurs. Sometimes, issues are not identified until the child begins attending school.

Who is more likely to get hypoxic ischemic encephalopathy?

While most cases of HIE cannot be prevented, some factors can make HIE more likely. Those include:

  • Preeclampsia (high blood pressure) in the child’s birth mother, or low blood pressure during delivery
  • Issues with the umbilical cord, uterus, or placenta
  • Maternal infections or infections in the fetus or newborn
  • Heart or lung problems
  • Anemia in the fetus
  • Internal bleeding by the birth mother and fetus
  • Problems during labor and delivery that restrict blood flow to the infant
  • Very premature births
  • Physical trauma to the brain or skull
  • Poor positioning during delivery (ex: shoulders getting stuck for prolonged periods during delivery)

How is hypoxic ischemic encephalopathy diagnosed and treated?

Diagnosing HIE

Diagnostic tests such as blood tests, spinal fluid tests, imaging tests (MRIs, ultrasounds), electroencephalograms (EEGs), and similar tools may be used to determine the causes of brain injuries. In newborns, an APGAR test, which looks at an infant’s skin color, heart rate, reflexes, muscle tone, and breathing, is used to assess an infant’s overall health and can help identify neonatal distress.

Treating HIE

There is no one treatment for infants and children with HIE. Treating the underlying cause of the disorder may improve symptoms. However, encephalopathy may cause permanent structural changes and irreversible damage to the brain.

Doctors may perform a cooling treatment (called therapeutic hypothermia), by which the infant’s brain and body are cooled down to reduce further injury and help protect the brain from the effects of losing oxygen and blood flow. This treatment may reduce the likelihood of severe disability and death.

Individuals whose heart, lungs, kidneys, or liver are damaged by HIE may receive treatments for their organ damage. Other treatments for HIE depend on the symptoms, severity, and the age of the child and may include:

  • Physical, speech, or occupational therapy
  • Feeding or swallowing therapy
  • Vision therapy, eyeglasses, or other corrective devices
  • Hearing therapy or hearing aids
  • Medications to prevent seizures (called anticonvulsants)

Scientists are studying interventions to help infants’ and children’s brains adapt and recover from injury (improving their neuroplasticity) and exploring novel treatments to improve outcomes for infants with HIE, including hormones, supplements, and stem cell treatments that may one day help the brains of people with HIE recover. Further research is needed to understand how care teams can best treat and support individuals with HIE.

Learn About Clinical Trials
Clinical trials are studies that allow us to learn more about disorders and improve care. They can help connect patients with new and upcoming treatment options.

How can I or my loved one help improve care for people with hypoxic ischemic encephalopathy?

Consider participating in a clinical trial so clinicians and scientists can learn more about HIE and related disorders. Clinical research uses human volunteers to help researchers learn more about a disorder and perhaps find better ways to safely detect, treat, or prevent disease.

All types of volunteers are needed—those who are healthy or may have an illness or disease—of all different ages, sexes, races, and ethnicities to ensure that study results apply to as many people as possible, and that treatments will be safe and effective for everyone who will use them.

For information about participating in clinical research visit NIH Clinical Research Trials and You. Learn about clinical trials currently looking for people with HIE at Clinicaltrials.gov.

Where can I find more information about hypoxic ischemic encephalopathy?

Information may be available from the following organizations:

National Institute of Child Health and Human Development (NICHD)
Phone: 800-370-2943

Hope for HIE
Phone: 248-574-8099

Order publications from the NINDS Catalog
The NINDS Publication Catalog offers printed materials on neurological disorders for patients, health professionals, and the general public. All materials are free of charge, and a downloadable PDF version is also available for most publications.