HIE Diagnosis Guide

Who Qualifies for Therapeutic Cooling? HIE Eligibility Criteria Explained

— Min Read

—

Quick Answer

Who qualifies for therapeutic cooling after HIE?

Cooling is offered to babies with moderate-to-severe HIE who meet a three-tier assessment: (1) evidence of a perinatal hypoxic-ischemic event, (2) moderate-to-severe encephalopathy on neurological exam (Sarnat 2 or 3), and (3) in many centers, an abnormal aEEG in the first 6 hours.
Standard eligibility: gestational age 35 weeks or above, birth weight 1800g or above, age less than 6 hours at start of cooling. Babies outside these ranges are usually excluded from standard protocols though some centers individualize.
Mild HIE, extreme prematurity, major congenital anomalies, uncontrolled bleeding, or severe head trauma generally exclude cooling in standard protocols.

Key Takeaways

The three main randomized trials establishing cooling (NICHD, TOBY, ICE) used slightly different criteria but agreed on the core framework: perinatal event + encephalopathy on exam, with aEEG as an additional supporting tool in some.
The most common reason a baby is not cooled is that the encephalopathy is judged mild. Recent research is examining whether mild HIE might also benefit, but cooling for mild HIE is not standard.
If your baby met criteria but was not cooled, or was cooled outside the window, these are specific questions worth asking and documenting.

Therapeutic cooling is the only proven treatment for HIE, and it meaningfully reduces the risk of death and disability when started within 6 hours of birth. But not every baby with a difficult birth qualifies. The decision follows a structured three-tier assessment based on evidence from three large randomized trials (NICHD, TOBY, ICE) and subsequent consensus guidance. For families whose baby was or wasn’t cooled, understanding exactly how the decision was made is central to understanding the NICU course. This guide walks through the criteria, the exclusions, the borderline cases, and the questions to ask when cooling decisions are unclear.

Why Cooling Matters

When a fetus experiences significant oxygen and blood flow deprivation, the initial injury to brain cells is only part of the picture. Over the next several hours after birth, a secondary phase of energy failure develops, driven by oxidative stress, inflammation, and excitotoxic neurotransmitter release. This secondary phase causes substantial additional injury to brain cells that initially survived.

Therapeutic hypothermia works by reducing this secondary injury. Cooling the body to approximately 33.5°C (92.3°F) slows the metabolic rate, reduces the inflammatory cascade, and limits excitotoxicity. The result, demonstrated in multiple randomized trials, is a meaningful reduction in death and disability when cooling is started within 6 hours of the injury.

What the cooling trials actually showed

The numbers from the landmark trials are worth knowing. The NICHD trial (Shankaran et al. 2005) randomized 208 term infants with moderate-to-severe HIE to cooling or standard care. Cooling reduced the combined rate of death or moderate/severe disability at 18 to 22 months from 62% to 44%. The TOBY trial (Azzopardi et al. 2009) enrolled 325 infants and showed similar reductions, particularly in the rate of disability among survivors. The ICE trial (Jacobs et al. 2011) confirmed the effect in an Australia/New Zealand cohort. The 2013 Cochrane meta-analysis combined the evidence and concluded that cooling reduces the risk of death or major neurodevelopmental disability, with a number needed to treat of approximately 7. Follow-up at school age (Azzopardi et al. 2014, NEJM; Shankaran et al. 2012, NEJM) has confirmed the benefits persist into later childhood.

The evidence base. The three landmark randomized trials (NICHD, Shankaran et al. 2005, NEJM; TOBY, Azzopardi et al. 2009, NEJM; and the ICE trial) each showed benefit. The 2013 Cochrane review by Jacobs et al. combined 11 trials of over 1,500 infants and confirmed cooling reduces the composite outcome of death or major disability, with a number needed to treat of approximately 7.

The Three-Tier Eligibility Framework

Most U.S. cooling protocols, consistent with the 2020 ACOG Committee Opinion 808, use a three-tier assessment:

Tier	What It Assesses	Typical Criteria
Tier 1	Evidence of perinatal hypoxic-ischemic event	Cord arterial pH ≤ 7.0, base deficit ≥ 16, OR Apgar ≤ 5 at 10 min, OR ongoing resuscitation at 10 min, OR sentinel event
Tier 2	Moderate-to-severe encephalopathy on neurological exam	Sarnat stage 2 or 3 (seizures, altered consciousness, abnormal tone and reflexes, autonomic dysfunction)
Tier 3 (where available)	Abnormal aEEG background	Abnormal pattern for ≥ 30 minutes in the first 6 hours, or clear seizures on aEEG

A baby meeting Tier 1 and Tier 2 (and Tier 3 if assessed) is typically offered cooling. A baby meeting Tier 1 but not Tier 2 (for example, acidemic but with only mild or no encephalopathy) is usually not cooled. A baby with encephalopathy but no clear perinatal event should also be evaluated for other causes (metabolic, infectious, stroke).

General Qualifying Criteria

Beyond the three-tier assessment, eligibility for standard cooling protocols requires:

Gestational age 35 weeks or above. Some centers cool late preterm babies (34-35 weeks) on an individualized basis.
Birth weight 1800g or above.
Age less than 6 hours at start of cooling. This is the single most important time-sensitive criterion.
Clinical team able to provide whole-body or head cooling with appropriate monitoring (some centers transfer in-borns to a regional cooling center rapidly to meet the 6-hour window).

Did Your Baby Qualify for Cooling, or Was It Not Offered?

Whether cooling was appropriately offered, delayed, or withheld is one of the most common case review questions. We can help you understand what the record shows.

Get a Free Case Review

Get a Free Case Review

Was your baby in the NICU after birth?

Confidential · No obligation · Takes 2 min

Who Is Typically Excluded From Cooling

Certain clinical situations generally exclude babies from standard cooling protocols:

Mild HIE (Sarnat stage 1 only). Babies with only mild encephalopathy generally have good outcomes without cooling, and the balance of benefits and risks has not been established. Recent research is examining mild HIE cooling, but it is not yet standard practice.
Extreme prematurity (below 34-35 weeks). Cooling in preterm infants has not been validated and may cause harm.
Very low birth weight (below approximately 1800g). Small babies are at increased risk of hypothermia-related complications.
Major congenital anomalies incompatible with life.
Severe head trauma or major intracranial hemorrhage.
Uncontrolled clinically significant bleeding.
Severe persistent pulmonary hypertension or profound hemodynamic instability that makes cooling unsafe.
Age beyond 6 hours at assessment (though some centers consider late cooling between 6 and 24 hours for selected babies).

Each individual case is reviewed by the neonatology team, and exclusion is a clinical judgment informed by the baby’s specific situation.

The Borderline Cases

Several clinical scenarios fall into gray zones where cooling decisions are individualized:

Late preterm infants (34-35 weeks): outside the original trials’ enrollment ranges, but some centers cool these babies with modified protocols when encephalopathy is clear.

“Mild HIE” with some concerning features: when the encephalopathy is between mild and moderate, or when aEEG shows abnormalities, some teams will proceed with cooling; others will closely observe.

Age 6 to 24 hours: the Late Hypothermia trial (Laptook et al. 2017, JAMA) did not definitively show benefit but did not exclude it. Some centers offer late cooling in selected cases.

Baby transferred from outside hospital: the 6-hour window includes transport time. Delayed recognition or delayed transfer can move a baby from eligible to ineligible.

Coexisting stroke, MAS, or persistent pulmonary hypertension: these conditions do not automatically exclude cooling, but require careful management.

The out-born baby problem. Many babies with HIE are born at community hospitals without cooling capability, then transferred to a regional NICU. The 6-hour clock does not stop for transfer. Recognition at the referring hospital, rapid communication with the cooling center, and expedited transport are all essential. Passive cooling during transport may be initiated to preserve eligibility.

How the Sarnat Exam Determines Stage

Sarnat staging is the core of the Tier 2 decision, and it is done by neurological exam, typically in the first hours of life. The neonatologist or pediatric neurologist examines six domains:

Domain	Mild (Stage 1)	Moderate (Stage 2)	Severe (Stage 3)
Level of consciousness	Hyperalert	Lethargic	Stupor/coma
Spontaneous activity	Normal or slightly decreased	Decreased	None
Muscle tone	Normal	Mildly hypotonic	Flaccid
Posture	Mild distal flexion	Strong distal flexion	Decerebrate
Primitive reflexes (suck, Moro)	Exaggerated	Weak	Absent
Autonomic function	Dilated pupils, tachycardia	Constricted pupils, bradycardia	Variable, unreactive pupils

Sarnat stage 2 or 3 in the first hours of life, combined with Tier 1 evidence, is the main indication for cooling. The exam is often repeated over the first 6 hours because encephalopathy can evolve.

6 hrsTime Window to Start

72 hrsDuration of Cooling

33.5°CTarget Core Temperature

~7Number Needed to Treat

When Cooling Decisions Warrant a Case Review

Cooling decisions can be the subject of a legal case review in specific scenarios:

A baby who met clear criteria was not cooled, often because the team misclassified the encephalopathy as mild or missed the 6-hour window.
A baby was not transferred promptly from an outside hospital to a cooling center within the window.
Cord blood gases were not obtained, making it impossible to establish Tier 1 criteria.
Sarnat staging was not properly documented in the first hours of life.
Cooling was started but terminated prematurely without clear clinical justification.
Cooling parameters (temperature, duration) deviated significantly from protocol.

A careful case review examines the complete NICU record: cord gases, Apgar scores, serial neurological exams, aEEG findings, transfer timeline, cooling initiation and completion times, and the neurological outcome. These documents together determine whether the cooling decision met the standard of care.

What parents can do during the decision window

Most cooling decisions happen within the first hours of life when parents are still processing the birth and may not feel positioned to advocate. A few things are worth doing anyway: ask directly whether your baby is being evaluated for cooling and why or why not. Ask what Sarnat stage has been documented and at what time. Ask whether aEEG is being considered if the encephalopathy assessment is borderline. If your baby was born at a hospital that does not offer cooling, ask whether transfer to a cooling center was considered and when, and ask about passive cooling during transport. Write down the answers with times. These early conversations are often incompletely recorded in the chart, and your contemporaneous notes can be the clearest record of what was said and when.

Was Cooling Started Late or Not Offered at All?

The 6-hour window and the decision to cool are both places where care can fall short. We can help you understand what the record shows.

Talk to Our Team

Get a Free Case Review

Was your baby in the NICU after birth?

Confidential · No obligation · Takes 2 min

Frequently Asked Questions

What is therapeutic hypothermia for HIE?

Therapeutic hypothermia, also called therapeutic cooling, is the evidence-based treatment for moderate-to-severe HIE. The newborn’s core body temperature is reduced to approximately 33.5°C (92.3°F) for 72 hours using either a whole-body cooling blanket or a selective head-cooling cap, then gradually rewarmed. Cooling reduces the secondary energy failure and inflammation that follow a hypoxic-ischemic event, which reduces the risk of death and disability when started within 6 hours of birth.

What are the standard eligibility criteria for cooling?

Standard criteria follow a three-tier approach. Tier 1 is evidence of a perinatal hypoxic-ischemic event (cord pH of 7.0 or lower, base deficit of 16 or greater, Apgar score of 5 or less at 10 minutes, need for continued resuscitation at 10 minutes, or a documented sentinel event). Tier 2 is moderate-to-severe encephalopathy on neurological exam (Sarnat stage 2 or 3). Tier 3, where available, is an abnormal aEEG background in the first 6 hours. Eligibility also requires gestational age 35 weeks or above, birth weight 1800g or above, and age less than 6 hours at start of cooling.

Why doesn’t my baby with mild HIE qualify for cooling?

The three randomized trials that established cooling (NICHD 2005, TOBY 2009, ICE 2011) enrolled only babies with moderate or severe encephalopathy. Mild HIE was excluded because babies with mild encephalopathy generally have good outcomes without cooling, and the potential benefits have not been shown to outweigh the risks in that group. Current guidelines therefore reserve cooling for moderate-severe HIE. Research is ongoing (notably the PRIME trial and COOL PRIME) to evaluate whether mild HIE might also benefit.

What are the main exclusions from cooling?

Standard exclusion criteria include: gestational age below 35 weeks (some centers cool 34-36 weekers on an individualized basis), birth weight below 1800g, age greater than 6 hours at identification, mild HIE only, major congenital anomaly incompatible with life, severe head trauma or intracranial hemorrhage, uncontrolled clinically significant bleeding, and some genetic or metabolic conditions. Each center’s protocol may differ slightly.

What are the differences between NICHD, TOBY, and ICE criteria?

All three used the same overall framework but differed in details. NICHD used whole-body cooling to 33.5°C for 72 hours and required evidence of perinatal event plus moderate-severe encephalopathy. TOBY, a UK trial, used similar criteria but included aEEG as an additional criterion in some protocols and used whole-body cooling. ICE, an Australian/NZ trial, also used whole-body cooling and similar enrollment criteria. The Cochrane review by Jacobs et al. (2013) combined the trials and confirmed consistent benefit across protocols.

Is aEEG required for cooling eligibility?

It depends on the protocol and the hospital. Some US centers require aEEG as part of the assessment (an abnormal aEEG supports proceeding to cool when clinical exam is borderline); other centers do not require it. The 2020 ACOG Committee Opinion 808 and the Cochrane review generally support aEEG as useful but not mandatory. In practice, if a baby meets Tier 1 and Tier 2 criteria clearly, cooling is usually started even without aEEG, and aEEG monitoring is initiated during cooling.

Can cooling happen after 6 hours of age?

Generally no, because the evidence base for benefit is strongest when cooling is started within 6 hours. However, there is some evidence that cooling begun between 6 and 24 hours may still offer benefit in selected cases. The Late Hypothermia trial (Laptook et al., 2017, JAMA) did not show definitive benefit for cooling started at 6 to 24 hours, but the results did not exclude benefit. A few centers will consider cooling in the 6 to 24 hour window for selected babies; this is generally a case-by-case decision.

What should parents ask if their baby was not offered cooling?

If your baby had evidence of a hypoxic-ischemic event but was not cooled, the useful questions are: What was my baby’s Sarnat stage? Was the encephalopathy considered mild or moderate, and who made that assessment? Were cord blood gases obtained? What was the 10-minute Apgar score? Was aEEG done, and what did it show? Was age at assessment within 6 hours? If an outside hospital identified the baby, was transfer to a cooling center considered? These answers clarify whether the decision was appropriate or whether it warrants review.

Cited Sources

Whole-Body Hypothermia for Neonates With Hypoxic-Ischemic Encephalopathy (NICHD Trial). Shankaran S, Laptook AR, Ehrenkranz RA, et al. New England Journal of Medicine, 2005.
Moderate Hypothermia to Treat Perinatal Asphyxial Encephalopathy (TOBY Trial). Azzopardi DV, Strohm B, Edwards AD, et al. New England Journal of Medicine, 2009.
Cooling for Newborns With Hypoxic-Ischaemic Encephalopathy (Cochrane Review). Jacobs SE, Berg M, Hunt R, Tarnow-Mordi WO, Inder TE, Davis PG. Cochrane Database of Systematic Reviews, 2013.
Hypothermia and Neonatal Encephalopathy (ACOG Committee Opinion No. 808). American College of Obstetricians and Gynecologists, 2020.
Neonatal Encephalopathy and Neurologic Outcome, Second Edition. ACOG / American Academy of Pediatrics Task Force, 2014.
Hypoxic-Ischemic Encephalopathy Information Page. National Institute of Neurological Disorders and Stroke (NINDS), NIH.

Who Qualifies for Therapeutic Cooling? HIE Eligibility Criteria Explained

Why Cooling Matters

What the cooling trials actually showed

The Three-Tier Eligibility Framework

General Qualifying Criteria

Who Is Typically Excluded From Cooling

The Borderline Cases

How the Sarnat Exam Determines Stage

When Cooling Decisions Warrant a Case Review

What parents can do during the decision window

Related reading for parents

Frequently Asked Questions