What Is Hypoxic Ischemic Encephalopathy?

Hypoxic ischemic encephalopathy (HIE) is a type of brain injury. It occurs when the baby’s brain doesn't receive enough oxygen or blood flow.

• Hypoxic = not enough oxygen
• Ischemic = not enough blood flow
• Encephalopathy = brain disorder

HIE is caused by a problem during labor and delivery. It's estimated to occur in between two and nine per 1,000 live births. Other terms for HIE include birth asphyxia, perinatal asphyxia and neonatal encephalopathy.

Grades of Hypoxic Ischemic Encephalopathy

The severity of HIE depends on how long the brain was without oxygen. Diagnosis can be broken into the following three categories:

Mild hypoxic ischemic encephalopathy: These symptoms include behavioral issues, such as poor sleep and feeding, irritability and crying. These cases typically resolve in 24 hours.

Moderate hypoxic ischemic encephalopathy: Symptoms of moderately severe HIE may include:

• Poor reflexes, including little or no grasping and sucking reflexes.
• Lethargy (extreme tiredness).
• Muscle weakness.
• Apnea (brief pauses in breathing).
• Seizures typically occurring within the first 24 hours.

Severe hypoxic ischemic encephalopathy: These symptoms are far more severe. They may include:

• Seizures within the first couple of hours after birth.
• Irregular breathing (often need a breathing tube).
• Coma.
• Problems with heart rate and blood pressure.
• Unusual eye motion or dilation.
• Muscle weakness.
• Absence of reflexes (including sucking, swallowing or grasping).

Hypoxic Ischemic Encephalopathy Causes

Perinatal hypoxic ischemic encephalopathy happens when a problem during labor and delivery restricts oxygen and blood flow to the baby’s brain.

Potential causes of HIE during labor and delivery can include:

• Excessive bleeding from the placenta (including tearing of the placenta).
• Very low blood pressure in the birthing parent.
• Umbilical cord problems.
• Rupture of the uterus.
• Abnormal fetal position, such as breech (feet first) position.
• Large baby getting stuck in the birth canal.
• Prolonged late stages of labor.
• Trauma to the brain or skull (such as use of forceps during delivery).

HIE is always diagnosed within the first few hours of delivery. Problems during pregnancy or after birth may also cause brain injury or dysfunction. However, because they do not occur around the time of delivery, those cases aren't classified as HIE.

Hypoxic Ischemic Encephalopathy Symptoms

Symptoms of HIE depend on the severity and extent of the brain injury. They also depend on which areas of the brain were affected. Babies born with HIE may:

• Be floppy and unreactive to sights or sounds.
• Be very tense and react more to stimulation than a healthy newborn.
• Have abnormal (not typical) movements or seizures.
• Have feeding problems due to weak muscles in their mouth and throat.
• Have a weak cry.
• Problems with the heart, lungs, kidneys and liver.
• Have low or high muscle tone.
• Have breathing problems.

Hypoxic Ischemic Encephalopathy Diagnosis

HIE may be suspected if a significant risk factor occurred during labor and delivery. HIE is diagnosed within the first six hours of life.

If your doctor suspects HIE, they will perform physical exams to monitor brain function. Diagnosis is based on physical exams, blood work, and details of labor and delivery. Once a baby has been diagnosed with HIE, a neurologist (brain specialist) will perform a second exam to confirm the diagnosis. A video electroencephalogram (EEG) is used to monitor for seizures and signs of brain dysfunction.

A series of neuroimaging tests, including a head ultrasound and magnetic resonance imaging (MRI), may also be done to create pictures of the brain. These pictures are used to detect brain injury, which can lead to developmental problems.

Hypoxic Ischemic Encephalopathy Treatment

Therapeutic hypothermia (also known as cooling therapy) is used to treat HIE. It’s used to treat babies who are full-term (at least 36 weeks gestation). Cooling therapy has not been proven to be safe for babies born prematurely.

Therapeutic hypothermia treatment for HIE is usually started within six hours of birth. Cooling therapy uses a cooling blanket and machine to lower your baby’s body temperature. Lowering body temperature helps prevent further brain injury from occurring. It typically lasts between 72 and 96 hours. Cooling slows the baby’s metabolic rate. This prevents further damage caused by normal oxygen and blood flow being restored too quickly. Cooling therapy helps stabilize the brain’s cells and reduces damaging inflammation. It helps reduce the likelihood of disability or death from HIE.

Cooling therapy for hypoxic ischemic encephalopathy is very safe. During this treatment, babies are given medicines to help them rest comfortably. They are closely monitored for any signs of discomfort. Lab work is done to monitor a baby’s metabolism, electrolytes and clotting factors. Brain activity will be checked with an EEG. After the cooling period, babies are slowly rewarmed to normal body temperature.

If low levels of oxygen affect other organs, babies may need other treatments. These may include use of a breathing machine, seizure medications and monitoring.

Hypoxic Ischemic Encephalopathy Prognosis

The outcome of babies with hypoxic ischemic encephalopathy depends on the severity of their condition. Cooling therapy can improve the chance of surviving HIE and living without disability.

Hypoxic ischemic encephalopathy in newborns may lead to more serious impairments later in life. These include cerebral palsy, breathing problems, and severe physical and intellectual disabilities. After HIE, treatment focuses on helping children adapt to symptoms caused by the brain injury.

After leaving the hospital, babies with HIE will visit the Newborn Intensive Care Follow-up Clinic at Cincinnati Children’s. The team will follow babies through the first few years of life. During these visits, babies will see a neonatologist and neurologist. They may also visit physical, occupational and speech therapists, as well as a nutritionist, depending on their needs.