Sarnat Staging: What are the Stages of Hypoxic-Ischemic Encephalopathy?

Birth Injury, Causes of Cerebral Palsy

thermometer and stopwatch with blue NICU baby in background

Hearing the news that your baby has a birth injury is never easy, and many parents want to understand as much as possible—as quickly as possible—about what their child is going through. Read on to learn about Hypoxic-Ischemic Encephalopathy (HIE), Sarnat scores, and what a Stage I HIE, Stage II HIE, or Stage III HIE diagnosis means for your child.

What is HIE?

HIE is a hypoxic-ischemic brain injury that occurs when a baby’s brain experiences oxygen deprivation and reduced blood flow to the brain. Here’s a breakdown of the HIE definition:

  • Hypoxic: Not enough oxygen
  • Ischemic: Not enough blood flow
  • Encephalopathy: A brain disorder

Not having enough oxygen and blood flow results in brain tissue damage that causes neurological dysfunction. When a baby’s brain is deprived of oxygen and blood flow during pregnancy, labor, and delivery, or in the postnatal period for more than a very short time, their brain will be affected.

Tragically, 40 to 60 percent of infants with severe cases of HIE die before two years of age or have severe, permanent cognitive and physical impairments like seizures, vision loss, cerebral palsy, or behavioral or learning disabilities.

Early indicators of HIE vary, but there are some common signs:

  • Unreactive to sights or sounds
  • “Floppy” muscle movement
  • Tense or reacting more to stimulation than a healthy newborn might
  • Abnormal movements or seizures
  • Feeding problems due to weak muscles in their mouth and throat
  • Weak crying sounds
  • Organ dysfunction, especially with the heart, lungs, kidneys, and liver

How Does HIE Happen?

Birth complications and other neonatal factors increase the risk of a baby developing HIE. The most significant risk factor for HIE is asphyxia during labor and delivery, which can have several causes:

There can be a combination of factors that contribute to your baby’s HIE, such as an umbilical cord complication resulting in prolonged late labor. HIE may be caused by multiple events, but ultimately brain injury occurs because of impaired blood flow and oxygen delivery to the brain. The degree of injury is classified using a three-stage system.

What Are the Stages of HIE?

A Sarnat score is a widely used tool used to classify the severity of a hypoxic-ischemic brain injury. The resulting classification may be referred to as a Sarnat stage.

  • Stage I describes conditions of mild HIE.
  • Stage II describes conditions of moderate to severe HIE.
  • Stage III describes conditions of severe HIE.

Stage I HIE

Stage I HIE is considered mild. During this time, your baby might experience a few worrisome symptoms, but they should last less than 24 hours after birth.

  • Hyper alertness
  • Possible slight “floppy” muscle tone
  • Overly brisk reflex responses
  • Strong Moro (startle) reflex
  • Dilated pupils (mydriasis)
  • Weak or absent suck reflex
  • Trouble sleeping
  • Jittery
  • Fast heart rate
  • Frequent crying

With Stage I HIE, babies generally do not experience seizures.

Stage II HIE

Stage II HIE can be considered either moderate or severe, depending on the extent of your baby’s symptoms. Symptoms of Stage II HIE generally last for about two to 14 days and require more medical attention than Stage I HIE.

  • Lethargy
  • “Floppy” muscle tone
  • Difficulty grasping with hands
  • Weak Moro (startle) reflex
  • Weak or absent suck reflex
  • Weak startle reflex
  • Trouble breathing/apnea
  • Seizures
  • Constricted pupils (miosis)
  • Abnormal wave activity

The Moro reflex that is typically still present in Stage I and Stage II HIE might look familiar to you. It’s best described as the feeling of falling you get when almost asleep followed by a reflex to “catch” yourself. You will often see your baby’s arms and legs shoot out quickly, as yours might if you ever experience this when falling asleep.


Stage III HIE is the most severe, and babies with Stage III HIE will be much less active and engaged. Officially, Stage III HIE can last for days or weeks but, like other birth injuries, the effects of any deprivation of oxygen or blood flow can be permanent.

  • Unresponsive, coma-like state
  • “Floppy” muscle tone all over
  • No response to physical stimuli or Moro reflex
  • Extreme difficulty with breathing
  • Absent neonatal reflexes, like sucking/swallowing
  • Vision problems
  • Dilated, fixed, or unresponsive pupils
  • Treatment-resistant seizures that begin/increase after 24 to 48 hours
  • Irregular heartbeat
  • Poor blood pressure
  • Irregular brain waves

According to a 2016 publication in the World Journal of Clinical Pediatrics, approximately 39 percent of babies with HIE are designated as mild, with 39 percent scoring moderate, and 22 percent scoring severe on the Sarnat scale.

How Is HIE Diagnosed?

Sarnat staging is determined by the symptoms of HIE as well as the areas of the brain that were affected, some of which can be seen immediately after birth:

  • Abnormal fetal heart rate tracings
  • Poor umbilical cord gasses (pH
  • Low Apgar scores
  • Presence of meconium-stained fluid
  • Respiratory support within the first several minutes of postnatal life

When HIE is suspected, healthcare professionals should assess your baby in a variety of areas, as well as rule out other causes of symptoms:

  • Mental status
  • Suck reflex
  • Moro (startle) reflex
  • Autonomic function (like breathing and heartbeat)
  • Pupils
  • Seizures
  • EEG (for brain wave activity)
  • Duration of symptoms

Neuroimaging methods, such as MRIs, also can be used to diagnose suspected cases of HIE. Doctors may suspect and test for HIE if a birth was traumatic or if a significant event, such as fetal injury or stroke, took place. Even if a child does not receive a diagnosis at birth, doctors and parents should continue to look for complications, which can include motor function impairment, developmental milestone delays, and delayed growth.

How is HIE Treated?

Treatment of HIE is possible, but medical staff must act quickly. HIE can be progressive, meaning that a swift diagnosis and intervention are required to have any chance of preventing worsening symptoms. HIE is fairly common, affecting from 1 to 6 out of every 1000 live births, and it is the leading cause of infant death. Treatment can be lifesaving, and it can also help mitigate severe and permanent neurological damage.

One of the first treatments a baby with HIE is likely to get is therapeutic hypothermia. Hypothermia therapy can slow down the injury process, which gives a baby’s brain the chance to heal, minimizing the chance of damage. Clinical evidence has shown that therapeutic hypothermia has helped full-term newborns with moderate to severe HIE, but it is crucial that babies undergoing therapeutic hypothermia are carefully monitored.

Treatment of HIE has made great leaps since the Sarnet stages were developed in 1976, and the kind of care that your baby gets will depend on which stage has been diagnosed. Other types of care or monitoring babies may receive include:

  • Respiratory support
  • Arterial line/umbilical artery catheter for blood pressure and arterial blood gas monitoring
  • Umbilical vein catheter for drawing blood
  • Control of hypotension, bradycardia, and/or apnea
  • Correction of too much acid in the body fluids
  • Maintenance of blood sugar
  • Fever control and seizure medication

When it comes to HIE, the best treatment is prevention whenever possible. Preventing birth asphyxia and HIE involves attentive medical care:

  • Close monitoring of the baby and mother to detect and respond to fetal distress
  • Careful delivery of the baby once signs of fetal distress are detected

Doctors should be equipped to take certain preventive measures during pregnancy and delivery. Furthermore, new moms can also take an active role in learning about prevention methods for HIE and advocating for themselves and their babies:

  • Understanding how electronic fetal monitoring can provide critical information to the delivery team and prevent injury
  • Confirming that the medical staff present during delivery have the necessary qualifications
  • Verifying that a certified and properly trained obstetrician and anesthesiologist or Certified Registered Nurse Anesthetist will be present during delivery
  • Knowing your rights as a patient, such as the right to a second opinion and the right not to be pressured into making a quick decision when unnecessary

During pregnancy, both the mother and the baby should receive regular prenatal testing to monitor fetal health and wellness. If a high-risk pregnancy is detected, referral to a maternal-fetal specialist may be necessary. Through careful monitoring and attentive care, healthcare professionals can usually detect and respond to indicators of hypoxic-ischemic encephalopathy.

What Is the Prognosis for Babies with HIE?

The prognosis for babies with HIE varies greatly, depending on the severity of the encephalopathy and the kind of post-birth intervention. Infants with mild, Stage I HIE generally survive, avoiding serious, long-lasting negative effects, but babies with Stage II and Stage III HIE are more likely to experience longer-lasting or even permanent effects. These include:

  • Stage II: 10 to 20 percent develop minor neurological conditions, and 30 to 50 percent develop more serious complications.
  • Stage III: 25 to 50 percent mortality rate, most often in the first few days after birth. Roughly 80 percent of babies who survive HIE develop serious complications like epilepsy, vision/hearing loss, cognitive impairment, and cerebral palsy.

Did Medical Malpractice Cause Your Child’s Cerebral Palsy?

Serious effects from HIE will typically last a lifetime, but it doesn’t mean your child cannot live a meaningful and full life, even with a condition like cerebral palsy. However, cerebral palsy treatments and support services can have a significant impact on your family finances. In some cases, cerebral palsy is, unfortunately, linked to poor medical care and could have been prevented. If you think this may be the cause of your loved one’s cerebral palsy, you might consider seeking legal help.

The Cerebral Palsy Family Lawyers at Janet, Janet & Suggs, LLC have consulted with over 30,000 families nationwide. We call upon our legal and medical experience to uncover the truth and seek the compensation families deserve. If your child suffered from medical malpractice that led to HIE and cerebral palsy, contact the Cerebral Palsy Family Lawyers at Janet, Janet & Suggs, LLC today for a free, no-obligation consultation.



Claire Surles, RN
Reviewed by:
Claire Surles, RN
Registered Nurse

Claire comes to JJS after a 10-year career as a labor and delivery nurse. She dedicated her hospital efforts to advocating for families, providing the safest birthing environment possible as Newborn Admission Nurse at UMMC St. Joseph Medical Center in Towson, Maryland. Her passion for helping those who experienced losses at any stage of gestation led to her appointment as Coordinator of the hospital’s ROOTS perinatal loss program. READ FULL BIO

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