Birth · Newborn
Sarnat HIE Staging
Sarnat & Sarnat 1976 staging for neonatal hypoxic-ischaemic encephalopathy. Three stages based on consciousness, tone, reflexes, pupils, and seizure activity. Stage II / III moderate-severe → therapeutic hypothermia eligibility.
Last reviewed 25 May 2026
Sarnat staging — neonatal HIE
Hypoxic-ischaemic encephalopathy stage I / II / III
Score all 7 domains to determine the Sarnat stage.
Educational tool only — not medical advice. Sarnat staging is performed by trained neonatologists. Stage II / III determination is THE eligibility criterion for therapeutic hypothermia, which must be initiated within 6 hours of birth. See the Therapeutic Hypothermia eligibility checker.
What does this mean?
Sarnat staging (1976) grades neonatal hypoxic-ischaemic encephalopathy by examination — a global synthesis of consciousness, tone, posture, primitive reflexes, autonomic function, and seizure activity. Stage I (mild) typically resolves with normal outcome. Stage II (moderate) and Stage III (severe) are the trigger for therapeutic hypothermia in babies ≥ 36 wk and ≤ 6 h of life — cooling to 33.5 °C for 72 h via whole-body or selective head cooling. The original NICHD, CoolCap, and TOBY trials showed cooling reduces death or major disability by ~25 % (NNT ~7). The Sarnat exam should be repeated at intervals because the picture evolves over the first 24–48 h. Adjuncts: aEEG, MRI brain on day 5–7, neurology and family-meetings throughout. Long-term follow-up to school-age is standard given the high neurodevelopmental risk.
Introduction
Sarnat & Sarnat (1976) described a 3-stage clinical-EEG classification of neonatal encephalopathy that remains the primary clinical staging system for hypoxic-ischaemic encephalopathy (HIE). The original purpose was to predict natural history; the modern purpose is to identify infants eligible for therapeutic hypothermia (cooling) within the 6-hour treatment window.
The three stages
Stage I — Mild
- Hyperalert / irritable
- Normal muscle tone
- Mild distal flexion
- Weak suck
- Strong / overreactive Moro
- Mydriasis (dilated pupils)
- No seizures
Typically resolves within 24-48 hours without intervention. Excellent prognosis.
Stage II — Moderate (cooling-eligible)
- Lethargic / obtunded
- Mild hypotonia
- Strong distal flexion
- Weak or absent suck
- Weak / incomplete Moro
- Miosis (constricted pupils)
- Common seizures
Stage III — Severe (cooling-eligible)
- Stupor / coma
- Flaccid muscle tone
- Decerebrate posturing
- Absent suck and Moro reflexes
- Variable / unequal pupils with poor light response
- Uncommon seizures (electrical activity may be suppressed)
How to interpret your result
- Stage I — observation; not cooling-eligible. Most resolve fully.
- Stage II / III — cooling-eligible if other criteria met. See the Cooling Eligibility calculator.
Cooling — why staging matters
Therapeutic hypothermia to 33.5 °C for 72 hours, started within 6 hours of birth, reduces death and severe neurodisability in moderate-to-severe HIE by ~25 % (Cochrane Jacobs 2013). The evidence comes from large randomised trials:
- NICHD Whole-Body Cooling trial (Shankaran NEJM 2005) — 208 infants.
- CoolCap (Gluckman Lancet 2005) — selective head cooling.
- TOBY (Azzopardi NEJM 2009) — 325 infants, whole-body cooling.
- Meta-analysis (Jacobs Cochrane 2013) — combined ~1,500 infants.
The 6-hour treatment window is critical — cooling started later is less effective. This makes accurate Stage II/III determination in the first few hours of life genuinely life-saving.
Limitations
- Inter-rater variability between experienced clinicians is good but not perfect.
- Subtle seizures may not be detected on clinical examination — aEEG / EEG complements the clinical assessment.
- Sedation, paralysis, or hypothermia can mask signs.
- Modified Sarnat scoring (Thompson 1997) is an alternative 9-item granular score used in some centres.
- Stage can deteriorate over hours — repeated assessment is essential before the cooling window closes.
- This is an educational tool; actual staging is by trained neonatologists.
Sources
- Sarnat HB, Sarnat MS. Neonatal encephalopathy following fetal distress: A clinical and electroencephalographic study. Arch Neurol 1976;33:696-705.
- Thompson CM, et al. The value of a scoring system for hypoxic ischaemic encephalopathy in predicting neurodevelopmental outcome. Acta Paediatr 1997;86:757-61.
- Jacobs SE, Berg M, Hunt R, Tarnow-Mordi WO, Inder TE, Davis PG. Cooling for newborns with hypoxic ischaemic encephalopathy. Cochrane Database Syst Rev 2013;1:CD003311.
- Shankaran S, et al. Whole-body hypothermia for neonates with hypoxic-ischemic encephalopathy. N Engl J Med 2005;353:1574-84. (NICHD)
- Azzopardi DV, et al. Moderate hypothermia to treat perinatal asphyxial encephalopathy. N Engl J Med 2009;361:1349-58. (TOBY)
- NICE. Hypoxic-ischaemic encephalopathy and neonatal encephalopathy (NG237).
Frequently asked questions
What is HIE?
Hypoxic-Ischaemic Encephalopathy — neurological injury from disrupted oxygen and blood flow to the fetal/newborn brain, typically related to a perinatal sentinel event (placental abruption, cord prolapse, uterine rupture, severe shoulder dystocia, severe pre-eclampsia/eclampsia). Affects 1-3 per 1,000 term births in high-income settings, higher in LMIC. Severe HIE is a leading cause of neonatal mortality and lifelong disability (cerebral palsy, learning disabilities, epilepsy, hearing/vision impairment).
What's the Sarnat staging system?
Sarnat & Sarnat (1976) described a 3-stage system based on neurological examination findings: Stage I (mild), Stage II (moderate), and Stage III (severe). Each stage encompasses level of consciousness, muscle tone, posture, primitive reflexes (Moro, suck), pupils, and seizure activity. Originally used to track natural history; now THE primary clinical criterion for therapeutic hypothermia eligibility.
Why does stage matter for cooling?
Therapeutic hypothermia (cooling to 33.5 °C for 72 hours) reduces death and severe neurodisability in moderate-to-severe HIE by ~25 % (Cochrane Jacobs 2013, NICHD 2005, TOBY 2008). It does NOT benefit (and may slightly harm) mild HIE. Accurate Sarnat staging — Stage II/III moderate-severe — is the EFL eligibility criterion. Stage I infants are observed but not cooled.
What other criteria must be met for cooling?
Per NICHD / TOBY criteria, ALL of: (1) GA ≥ 36 weeks; (2) age ≤ 6 hours; (3) Sarnat Stage II or III; (4) evidence of perinatal depression — Apgar ≤ 5 at 10 minutes, OR need for ongoing resuscitation at 10 min, OR cord arterial pH < 7.0 or base deficit ≥ 16. All four must be met. See the Cooling Eligibility calculator.
What's the prognosis at each stage?
Stage I — typically excellent; most resolve without sequelae. Stage II — historical outcomes: ~25 % moderate-severe disability or death; cooling reduces this to ~15 %. Stage III — historical outcomes: ~75 % death or severe disability; cooling reduces this somewhat (number needed to treat 6-8 to prevent one death/disability). The depth of stage and EEG findings (continuous voltage suppression worse than burst-suppression worse than discontinuous) refine prognosis.
Is Sarnat staging objective?
Moderately. The original Sarnat description requires bedside neurological examination by experienced clinicians; inter-rater agreement is good but not perfect. Modified Sarnat scoring (Thompson 1997, an alternative 9-item score 0-27) is more granular and is used in some centres. EEG and aEEG complement the clinical assessment, particularly for distinguishing Stage II from Stage III and for detecting subclinical seizures.
When is the stage assessed?
Repeatedly through the first hours of life. Initial assessment in delivery room or NICU; repeated at 1, 3, 6 hours. Stage can deteriorate (especially Stage I → Stage II) over the first 6 hours — the cooling window. Centres aim to identify Stage II/III by 3-6 hours to start cooling before the 6-hour window closes.