Hypoxic-Ischemic Encephalopathy (HIE)

What is hypoxic-ischemic encephalopathy (HIE)?

Hypoxic-ischemic encephalopathy (HIE) is a brain injury that occurs when your brain doesn’t get enough blood and oxygen. This can permanently change how your brain functions. HIE usually affects newborns who had a difficult birth, but it can also affect older children and adults who experience severe respiratory distress like drowning.

HIE is a life-threatening condition. Call 911 or seek medical attention right away if you or your child have symptoms of HIE.

You may hear your newborn’s healthcare provider refer to HIE as:

• Birth asphyxia.
• Neonatal encephalopathy.
• Perinatal hypoxia.

What are the types of hypoxic-ischemic encephalopathy?

A healthcare provider will grade HIE based on your child’s prognosis. These include mild, moderate or severe. These grades can affect neurological outcomes. All grades of HIE require emergency medical attention to prevent life-threatening complications. Your healthcare provider can best explain your child’s outlook so you know what to expect.

How common is hypoxic-ischemic encephalopathy?

HIE affects an estimated 1 to 6 infants out of every 1,000 births. In the United States, this equals about 9,000 to 12,000 newborns each year.

What are the signs and symptoms of HIE?

Mild and moderate signs and symptoms of HIE in newborns include:

• A floppy, weak muscle tone (hypotonia) or tense muscles (hypertonia).
• Difficulty feeding.
• Fatigue.
• Irritability.
• A weak cry.
• A pale, blue or gray tone to their skin, fingers and lips (cyanosis).

Severe symptoms of HIE in newborns include:

• Little to no response to touch or sound.
• Poor reflexes.
• Abnormal breathing patterns.
• An irregular or slow heartbeat.
• Seizures.
• Loss of consciousness.

If your child experiences any of these signs or symptoms, call 911 or your local emergency services number. Even mild HIE is an emergency and requires immediate medical attention.

What causes hypoxic-ischemic encephalopathy?

An interruption of blood and oxygen supply to your brain causes HIE. There are several ways that this could happen.

Causes of HIE during fetal development include:

• Abnormal development or function of a fetus’ heart or lungs.
• An infection (toxoplasmosis or CMV).
• Blood pressure that’s too high or too low in the pregnant parent.
• Low oxygen levels in the pregnant parent.

Pregnant parents who experience a difficult pregnancy or delivery may be more at risk of having a child with HIE. Examples may include:

• The umbilical cord drops out of place before the fetus (cord prolapse).
• Umbilical cord compression or the flow of blood in the cord stops.
• The placenta separates from the uterus (placental abruption).
• The uterus tears open (uterine rupture).
• The placenta blocks the cervix (placenta previa).

Causes of HIE in older children and adults may include events that make breathing difficult (respiratory distress) like:

• Arrhythmia.
• Asphyxiation (like drowning or strangulation).
• Overdose.
• Poisoning (like mercury poisoning).
• Shock.

What are the risk factors for hypoxic-ischemic encephalopathy?

An infant may be more at risk of HIE if they have:

• A low birth weight.
• Amniotic fluid contamination.
• Delayed fetal development (certain organs, like the lungs, didn’t develop completely).

A pregnant parent has a higher risk of delivery complications if they experience the following:

• Preeclampsia.
• Gestational diabetes.
• Prolonged labor.
• Substance use disorder.

What are the complications of hypoxic-ischemic encephalopathy?

HIE is a serious condition that can be fatal. It can also lead to complications caused by permanent brain damage, including:

• Developmental delays.
• Problems with growth.
• Hearing or vision loss.
• Issues with cognitive function (intellectual disability).
• Difficulty paying attention.
• Epilepsy.
• Cerebral palsy.
• Infections.

Many complications don’t appear until around the time your child starts school. If you notice your child misses developmental milestones or struggles in the classroom, contact their healthcare provider.

How is HIE diagnosed?

As HIE is a medical emergency, healthcare providers look for signs of the condition before and after your baby is born to make sure their brain receives enough oxygen and blood. If your baby experienced a difficult birth, healthcare providers prepare to treat this condition immediately, often before making an official diagnosis.

To diagnose hypoxic-ischemic encephalopathy, a healthcare provider will perform a complete physical exam. They’ll look for signs and symptoms of the condition and run tests to confirm a diagnosis.

For HIE in babies, tests may happen before your baby is born and after, including:

• Fetal heart monitoring.
• Placenta blood test.
• Newborn wellness assessment (Apgar score).
• Cord blood and gases test.
• Imaging tests like an ultrasound or an MRI.
• An EEG.

Additional blood tests may help your healthcare provider understand more about how HIE affected your newborn’s organs.

What is the treatment for HIE?

A healthcare provider treats HIE by:

• Cooling your baby’s body (therapeutic hypothermia), followed by rewarming their body to an expected temperature. This can help protect the brain from further injury.
• EEG monitoring to detect seizures during your or your child’s hospital stay, as well as antiseizure medications to prevent them.
• Supportive treatment of the underlying cause to improve blood and oxygen flow to you or your child’s brain (like receiving supplemental oxygen through a mask or nasal cannula).

If complications arise as your child grows, they may need additional support like:

• Physical or occupational therapy.
• Speech therapy.
• Early intervention educational programs.
• Assistive devices like glasses or hearing aids.

Are there side effects of the treatment?

Antiseizure medications may have side effects. They vary based on which one your healthcare provider prescribes. Before treatment begins, talk to your child’s healthcare provider about the possible side effects of treatment and what signs to look out for. Therapeutic hypothermia can also have side effects, such as low platelets.

How soon after treatment will my child feel better?

Newborns with mild symptoms and no brain damage will make a full recovery in about two weeks. More severe cases can cause lifelong complications that need long-term management to help you or your child feel better.

Can hypoxic-ischemic encephalopathy be prevented?

There isn’t a way to prevent all cases of HIE.

You can reduce your risk of having a child with HIE by visiting your pregnancy care provider for regular checkups during pregnancy. Your healthcare provider can give you advice on how you can stay safe and maintain good health. Unfortunately, HIE can still happen even if you’re in good health during pregnancy.

It’s also important to manage substance use disorder to prevent complications that may affect you and your baby.

Older children and adults can prevent HIE by taking safety precautions before participating in potentially dangerous activities. For example, only swim in areas where there’s a lifeguard on duty to prevent drowning.

What can I expect if my baby has hypoxic-ischemic encephalopathy?

The severity of HIE can affect your newborn’s outcome. Research estimates that HIE is fatal for 20% to 50% of infants. An estimated 25% to 60% of infants have long-term neurological (brain and nerve) conditions like cerebral palsy or epilepsy or issues with cognitive function (learning disability).

Can a baby fully recover from HIE?

Yes, a full recovery after HIE is possible in some cases. Prompt HIE treatment can prevent brain damage, leading to the best outcome. Unfortunately, not all babies make a complete recovery.

What’s the life expectancy for a baby with HIE?

Severe HIE shortens life expectancy. A newborn may die during infancy or early childhood if they have severe brain damage. Mild HIE usually doesn’t affect how long you live. Moderate HIE may or may not shorten your life expectancy. Most infants with mild to moderate HIE have a normal life expectancy. Supportive treatment is available to reduce your baby’s risk of life-threatening outcomes.

When should I see a healthcare provider?

Contact your child’s healthcare provider if they miss developmental milestones for their age or show signs of complications as they grow. If your child has trouble feeding, contact their healthcare provider.

When should I go to the ER?

Contact 911, local emergency services or visit the emergency room if you, your child or a loved one have signs or symptoms of HIE including:

• Difficulty breathing.
• A seizure.
• A pale, blue or gray color to your or their skin.
• Loss of consciousness (passing out).

What questions should I ask my doctor?

• How severe is HIE?
• Does my newborn have brain damage?
• What complications should I look out for?
• Are there side effects of the treatment?
• When can my child leave the hospital?
• When should I schedule follow-up appointments to monitor their health?