Authors: Akash Virupakshaiah, MD;  Sonika Agarwal, MBBS, MD 
Children’s Hospital of Philadelphia , Perelman School of Medicine at the University of Pennsylvania  

Reviewed: June 2021 

Disorder Overview

SUMMARY

Hypoxic ischemic encephalopathy (HIE) is a type of brain disorder or dysfunction that occurs early in life. It is due to a combination of: 

• Hypoxia: when brain does not receive enough oxygen for a period of time 
• Ischemia: when blood flow to the brain is restricted for a period of time 
• Encephalopathy: a brain disorder or dysfunction of the brain 

HIE is one type of neonatal encephalopathy (NE). NE is a broad term referring to several brain-related conditions in newborns. NE conditions cause problems in babies’ central nervous systems. The problems begin within the first several days after birth.  HIE can happen before birth (during pregnancy), at birth, or immediately after birth. HIE is a relatively rare event, occurring in 2 to 4 of every 1,000 births. 

Symptoms and outcomes vary. They depend on the cause and severity of the HIE. Some children experience no health issues. Some have mild to moderate effects. Still others have more severe effects. Severe HIE can cause permanent disability and affect development. It can lead to developmental delay. It can also lead to cerebral palsy, seizures, epilepsy and/or cognitive impairment. 

Like the brain, other organs are also dependent on blood supply and oxygen. A reduced blood or oxygen supply can affect these organs, too. For instance, the heart, liver, kidneys, and bowels may be affected alongside the brain. These organs may not function normally. Sometimes, affected organs can recover complete function. However, if the brain sustains injury, it may lead to long-term neurodevelopmental deficits. The duration and severity of the hypoxia and ischemia matter. They determine the severity of any deficits in development and otherwise. 

CAUSES

SIGNS AND SYMPTOMS

Symptoms of HIE vary. They depend primarily on the severity of the underlying brain damage. The symptoms can be divided into three types: mild, moderate, and severe. 

Severe HIE 

Symptoms of severe HIE include: 

PREVENTION 

HIE can sometimes be prevented by appropriately managing maternal risk factors and early diagnosis and management of pregnancy related complications. 

First, risk factors can be reduced with care throughout pregnancy. Regular visits with a health care provider are essential. 

These prenatal visits can: 

• Help with management of medical complications during pregnancy 
• Help with immunizing mother   
• Prevent low birth weight  
• Prevent premature birth 
• Proper nutrition and vitamin supplements 

Second, avoiding maternal bodily injuries is important. 

For instance, it helps to: 

• Wear a seat belt 
• Use a bike or motorcycle helmet 
• Avoid risky exercises and behaviors 

Third, alcohol, tobacco, and illegal drugs have been linked to HIE. Avoiding them can lower the risk of HIE. 

DIAGNOSIS 

HIE is suspected based on: 

• Known risk factors 
• Pregnancy and labor/birth history 
• Medical records from birth documenting fetal:  
• Heart rate 
• Activity 
• Color 
• Movements 
• Breathing 
• Requirements for support and resuscitation around time of birth 

To diagnose HIE, a complete physical exam is performed. The medical team examines the baby for symptoms and signs of HIE. Additional labs may help aid the diagnosis. For instance, cord blood tests can help.  

Once a diagnosis is suspected, a baby is usually monitored for signs of brain dysfunction. For instance, they may be checked for seizure activity. This is done using an electroencephalogram (EEG). An EEG measures the electrical activity of the brain. Then, continuous video monitoring is used as available. Video helps because signs of seizures may be very subtle and not noticeable in babies.  

Magnetic resonance imaging (MRI) is also used. MRI can take pictures of the brain. It can look for signs of brain injury. It can also look for other causes for encephalopathy, such as:  

• Stroke 
• Hemorrhage (bleeding) 
• Brain malformations.  

TREATMENT AND THERAPIES 

Treatment begins as soon as a diagnosis of HIE is made. This starts in the neonatal intensive care unit (NICU).  

Here is what to expect in the NICU: 

Here is what to expect after discharge from the NICU: 

OUTLOOK

Outcomes vary depending on the severity of HIE. Some babies do well. They may not have long-lasting effects. Others may require extensive support. They may be intellectually disabled.  

Some long-term complications can result from HIE.

They include:  

Research 

ClincalTrials.gov for Neonatal Hypoxic Ischemic Encephalopathy and Neonatal Encephalopathy are clinical trials that are recruiting or will be recruiting. Updates are made daily, so you are encouraged to check back frequently.  

ClinicalTrials.gov is a database of privately and publicly funded clinical studies conducted around the world. This is a resource provided by the U.S. National Library of Medicine (NLM), which is an institute within the National Institutes of Health (NIH). Listing a study does not mean it has been evaluated by the U.S. Federal Government. Please read the NLM disclaimer for details.   

Before participating in a study, you are encouraged to talk to your health care provider and learn about the risks and potential benefits.  

The information in the CNF Child Neurology Disorder Directory is not intended to provide diagnosis, treatment, or medical advice and should not be considered a substitute for advice from a healthcare professional. Content provided is for informational purposes only.  CNF is not responsible for actions taken based on the information included on this webpage. Please consult with a physician or other healthcare professional regarding any medical or health related diagnosis or treatment options. 

Douglas-Escobar M, Weiss MD. Hypoxic-ischemic encephalopathy: a review for the clinician. JAMA Pediatr. 2015 Apr;169(4):397-403. doi: 10.1001/jamapediatrics.2014.3269.PMID: 25685948 Review. 

Yıldız EP, Ekici B, Tatlı B. Neonatal hypoxic ischemic encephalopathy: An update on disease pathogenesis and treatment. Expert Rev Neurother. 2017 May;17(5):449-459. PMID: 27830959; https://doi.org/10.1080/14737175.2017.1259567 

C. Weeke, MD, PhD, Floris Groenendaal, MD, PhD , Kalyani Mudigonda, MD , Mats Blennow, MD, PhD , Maarten H. Lequin, MD, PhD , Linda C. Meiners, MD, PhD, Ingrid C. van Haastert, MA, PhD , Manon J. Benders, MD, PhD, Boubou Hallberg, MD, PhD, , and Linda S. de Vries, MD, PhD. A Novel Magnetic Resonance Imaging Score Predicts Neurodevelopmental Outcome After Perinatal Asphyxia and Therapeutic Hypothermia Lauren. J Pediatr 2018;192:33-40.