What Clinical Signs Define Sarnat Stages in Newborn HIE?

When doctors suspect your baby might have Hypoxic-Ischemic Encephalopathy (HIE), they perform a specific neurological physical exam called the modified Sarnat exam. Seeing your baby being examined in the NICU can be overwhelming and frightening, but understanding what the doctors are looking for can help you follow their care plan.

The Sarnat exam evaluates several key areas of your baby’s brain and nerve function to grade the severity of the injury as Stage 1 (mild), Stage 2 (moderate), or Stage 3 (severe) ^[1]. This staging is a “snapshot” of your baby’s condition at that moment. Clinicians use it alongside other factors—like the birth history, lab results (such as blood gases), and gestational age—to guide time-sensitive treatments ^[2]. For example, certain moderate or severe physical findings, combined with these other factors within the first six hours of life, may determine if a baby is eligible for therapeutic hypothermia (cooling therapy) ^[2][3].

The Core Areas Assessed

The Sarnat exam requires doctors to look at the whole picture rather than focusing on a single sign ^[4]. They evaluate six main clinical areas (domains) ^[2]:

1. Level of Consciousness: Is the baby overly alert, extremely sleepy (lethargic), or unresponsive (comatose)?
2. Spontaneous Activity: How much is the baby moving on their own?
3. Posture: How does the baby hold their arms and legs?
4. Muscle Tone: Are the baby’s muscles stiff (hypertonic) or loose and floppy (hypotonic)?
5. Primitive Reflexes: Doctors test natural newborn reflexes, such as the suck reflex and the Moro (startle) reflex, to see if they are normal, weak, or absent ^[5].
6. Autonomic Function: Doctors check involuntary functions, including pupil size, heart rate, and breathing patterns.

Additional Seizure Assessment: Seizures are also closely evaluated. Doctors monitor for abnormal physical movements and use brain wave monitoring to detect seizures that cannot be seen with the naked eye ^[1][6].

The Three Stages of HIE

A baby does not need to have every symptom in a category to be placed in a specific stage. In many hospital protocols, if a baby shows moderate or severe signs in at least three of the six domains, they may meet the neurological criteria for cooling therapy ^[2].

Stage 1: Mild HIE

In mild HIE, the baby’s nervous system is overstimulated or irritated.

• Consciousness & Activity: The baby may be hyper-alert, fussy, or unusually irritable ^[1].
• Tone & Posture: Muscle tone might be normal or slightly stiff ^[1].
• Reflexes: The baby may have poor feeding or a weak suck, alongside an overly sensitive startle reflex ^[1][5].
• Seizures: Clinical seizures are not typically seen in Stage 1 ^[1].

Stage 2: Moderate HIE

In moderate HIE, the baby’s brain activity and physical responses slow down significantly.

• Consciousness & Activity: The baby often appears extremely sluggish, sleepy, or lethargic, with decreased spontaneous movement ^[1].
• Tone & Posture: The baby’s muscles are usually floppy and loose ^[1].
• Reflexes: The suck reflex and startle reflex are noticeably weak or impaired ^[1].
• Seizures: Visible clinical seizures are common in moderate HIE ^[1].

Stage 3: Severe HIE

Severe HIE indicates significant depression of the baby’s brain function.

• Consciousness & Activity: The baby is unresponsive, in a stupor, or in a coma, with no spontaneous movement ^[1].
• Tone & Posture: The baby is extremely floppy with no muscle resistance, known as being flaccid ^[1].
• Reflexes: Primitive reflexes like sucking and startling are completely absent ^[1].
• Seizures: Because brain activity is profoundly suppressed in severe HIE, visible clinical seizures are often less common than in Stage 2. However, hidden electrical seizures can still occur, making brain monitoring critical ^[1][6].

Why Doctors Check Multiple Times

Your baby’s Sarnat score isn’t just a one-time test, nor does a single early exam definitively predict their long-term future. A baby’s neurological condition can evolve rapidly after birth. In one large registry study, nearly 75% of babies showed changes in their neurological scores—either improving or worsening—during these early hours ^[3].

For this reason, doctors perform serial assessments (repeated exams). It is also important to know that medications (like sedatives or antiseizure drugs), prematurity, and cooling therapy itself can temporarily change a baby’s alertness, tone, and reflexes ^[7][8]. Parents should not feel burdened to diagnose or interpret these signs themselves, as the care team knows how to account for these variables.

Electrographic-Only Seizures and Brain Monitoring

Physical signs alone are not always enough to understand a baby’s brain function, especially regarding seizures. Babies with HIE frequently have electrographic-only seizures, meaning their brain is having a seizure but their body is not making any abnormal movements ^[9]. During cooling therapy, it is common for physical seizure movements to stop while the brain continues to seize ^[9].

Because observing movements alone cannot reliably confirm or exclude a seizure, doctors often use an EEG (electroencephalogram) to monitor the baby’s brain waves ^[6][2]. This monitoring helps the care team detect hidden seizures and guide appropriate treatment.