Perinatal Asphyxia/Hypoxic Ischemic Encephalopathy (HIE): Case Discussion & Key Points
Model Case Presentation
Patient Demographics
Name: Baby of Mrs. Priya Sharma, Age: Day 1 of life (18 hours), Gender: Male, Gestational Age: 39 weeks, Informant: Mother (Reliable)
Chief Complaints
- Baby not crying well after birth
- Reduced movements and poor feeding since birth
- One episode of abnormal twitching movements at 6 hours of life
History Summary
The mother is a 26-year-old G2P1L1. The antenatal period was uneventful until the onset of labour. Labour lasted 18 hours (prolonged). During the second stage, meconium-stained liquor (thick, Grade 3) was noted. Fetal heart rate showed late decelerations on cardiotocography. Emergency LSCS was performed for fetal distress. Baby was delivered with Apgar score 2 at 1 minute and 4 at 5 minutes. Positive pressure ventilation was required for 4 minutes in the delivery room before the baby established regular breathing. Birth weight was 3.2 kg.
Since birth, the baby has been lethargic, not feeding, with reduced spontaneous movements. The mother noted the baby's eyes seemed to deviate to one side with repetitive jerking of the right arm at 6 hours — lasting approximately 2 minutes (likely a neonatal seizure). No family history of seizures or metabolic disorders.
Examination Summary
| Parameter | Finding | Significance |
|---|---|---|
| Tone | Generalized hypotonia ("floppy baby") | Hypoxic brain injury |
| Consciousness | Obtunded — responds only to painful stimuli | Moderate HIE |
| Suck reflex | Absent | Brainstem dysfunction |
| Moro reflex | Incomplete (arms flex only, no extension) | Moderate HIE |
| Pupils | Miosis, sluggishly reactive to light | Parasympathetic dominance (Stage 2) |
| Seizures | Focal clonic (right arm) | Most common seizure type in HIE |
| HR | 140/min | Normal |
| RR | 52/min, irregular | Periodic breathing — respiratory center involvement |
| Temperature | 37.2°C | Hyperthermia worsens outcome |
Other system findings: Fontanelle full but not bulging. Grasp reflex reduced. DTRs diminished. No facial dysmorphism. Cardiovascular and respiratory examinations within normal limits. Liver not enlarged.
✅ Complete Diagnosis
Hypoxic Ischemic Encephalopathy — Moderate (Sarnat Stage II / Grade 2), in a term neonate, following intrapartum asphyxia (prolonged labour, thick meconium-stained liquor, late decelerations, Apgar 2/1 min), with neonatal seizures (focal clonic). Eligible for Therapeutic Hypothermia.
📝 History — Exam Q&A
HIE is a clinical syndrome of disturbed neurological function in a neonate ≥35 weeks gestation, resulting from impaired cerebral blood flow and/or oxygen delivery during the perinatal period. It is characterised by reduced level of consciousness, abnormal tone, depressed or absent primitive reflexes, seizures, and/or apnoea, occurring in the setting of a hypoxic-ischaemic insult.
💡 Important distinction
Neonatal Encephalopathy (NE) is the broader term for disturbed neurological function. HIE is the subset due to hypoxia-ischaemia. Less than 30% of all neonatal encephalopathy cases meet criteria for true intrapartum HIE.
- Developed countries: 1.5–2.5 per 1000 live births
- Developing countries (including India): Up to 26–30 per 1000 live births
- Responsible for ~23% of all neonatal deaths worldwide (~840,000 deaths/year)
- Most common cause of neonatal seizures and subsequent cerebral palsy in term infants
Maternal/Antepartum causes:
- Maternal hypotension, hypertension (pre-eclampsia/eclampsia)
- Diabetes, severe anaemia, cardiac/respiratory disease
- Abnormal fetal growth (IUGR, macrosomia)
Intrapartum causes (most common):
- Cord prolapse, cord compression
- Abruptio placentae, placenta praevia
- Uterine rupture, abnormal uterine contractions
- Prolonged labour, shoulder dystocia
- Maternal cardiac arrest
Postnatal causes:
- Severe respiratory distress, cardiac arrest
- Severe hypoglycaemia, meningitis
- Evidence of an acute perinatal hypoxic event (see above)
- Meconium-stained amniotic fluid (especially thick/Grade 3)
- Low Apgar score — particularly ≤3 at 5 minutes or ≤5 at 10 minutes
- Need for resuscitation at birth (PPV, cardiac compressions, adrenaline)
- Abnormal fetal heart rate monitoring (late decelerations, prolonged bradycardia)
- Postnatal features: Lethargic/irritable, not feeding, seizures, abnormal tone, apnoea
ALL of the following must be present:
- Profound metabolic or mixed acidaemia (umbilical artery pH < 7.0 or base deficit ≥ 12–16 mmol/L)
- Apgar score 0–3 persisting for more than 5 minutes
- Neonatal neurological sequelae (seizures, coma, hypotonia)
- Multi-organ involvement (kidneys, lungs, liver, heart, gut)
Hypoxia-ischaemia → ↓ cerebral oxygen delivery → failure of oxidative phosphorylation → ↓ ATP
Phase 1 — Primary Energy Failure (during insult):
- ATP depletion → failure of Na/K ATPase pump → intracellular Na/Ca influx, cellular oedema
- Anaerobic glycolysis → lactic acidosis
- Release of excitatory neurotransmitters (glutamate) → NMDA receptor overstimulation → excitotoxicity
Latent Phase (1–6 hours after insult): Partial restoration of oxidative metabolism — this is the "therapeutic window" for cooling.
Phase 2 — Secondary Energy Failure (6–72 hours):
- Re-oxygenation paradox → free radical formation → oxidative stress
- Inflammation, apoptosis cascade
- Cerebral oedema, ongoing neuronal death
💡 Why cooling works
Therapeutic hypothermia acts during the latent phase, before secondary energy failure. It is ineffective if started after 6 hours (when secondary failure is established).
- No maternal fever/chorioamnionitis — rules out neonatal meningitis/sepsis
- No consanguinity, no family history of similar illness — rules out inborn errors of metabolism
- No maternal drug use (opioids, magnesium toxicity) — drug-induced depression
- No antenatal CNS malformation on ultrasound — structural brain anomaly
- No history of trauma — intracranial haemorrhage
- Normal blood sugar — hypoglycaemia can mimic HIE
- No fetomaternal haemorrhage, maternal thrombocytopenia
MSAF occurs in 10–15% of all deliveries. It can be a sign of fetal distress (fetal hypoxia causing vagal stimulation → intestinal hyperperistalsis → passage of meconium in utero).
Grading of MSAF: Grade 1 (thin, watery) → Grade 2 (moderate) → Grade 3 (thick, pea-soup — highest risk of MAS).
Thick MSAF + fetal distress (abnormal CTG) is a significant risk factor for HIE. However, MSAF alone does not diagnose HIE — it must be accompanied by evidence of encephalopathy.
Meconium Aspiration Syndrome (MAS) — aspiration of meconium into airways, causing chemical pneumonitis, airway obstruction, and pulmonary hypertension — can worsen hypoxia and compound HIE.
| Organ | Manifestation |
|---|---|
| Brain (72%) | HIE, seizures, cerebral oedema |
| Kidneys | Acute tubular necrosis, oliguria, elevated creatinine (most common after brain) |
| Heart | Transient myocardial ischaemia, tricuspid regurgitation, poor contractility |
| Lungs | MAS, Persistent Pulmonary Hypertension of Newborn (PPHN), RDS |
| Liver | Elevated transaminases (AST > ALT), coagulopathy |
| Gut | Necrotizing Enterocolitis (NEC), feed intolerance |
| Adrenals | Adrenal haemorrhage, adrenal insufficiency |
| Haematology | Thrombocytopenia, DIC, polycythaemia |
🩺 Examination — Exam Q&A
The Modified Sarnat Staging (Sarnat & Sarnat, 1976) classifies HIE into three stages based on clinical neurological examination. It is assessed ideally within the first 6 hours of life:
| Feature | Stage 1 (Mild) | Stage 2 (Moderate) | Stage 3 (Severe) |
|---|---|---|---|
| Level of Consciousness | Hyperalert, irritable | Obtunded, lethargic | Stuporous, comatose |
| Tone | Normal or slightly increased | Mild-moderate hypotonia | Flaccid (severe hypotonia) |
| Posture | Mild distal flexion | Strong distal flexion | Decerebrate |
| Suck Reflex | Weak but present | Weak/absent | Absent |
| Moro Reflex | Exaggerated | Weak, incomplete | Absent |
| Pupils | Mydriasis (dilated) | Miosis (constricted), reactive | Fixed, poorly reactive |
| Seizures | None (or brief) | Frequent (focal/multifocal) | Frequent or absent (brain too damaged) |
| Respiration | Normal | Periodic, may need support | Apnoea, ventilator-dependent |
| EEG | Normal | Low voltage, periodic pattern | Burst suppression, isoelectric |
| Duration | <24 hours | 2–14 days | Hours to weeks |
| Outcome | Normal | 20–35% neurological deficit | High mortality; near-universal sequelae in survivors |
🚨 Key Point
Therapeutic hypothermia is indicated for Sarnat Stage 2 and 3 (moderate and severe HIE) in infants ≥36 weeks gestation when initiated within 6 hours of birth.
Assess systematically:
- Level of consciousness: Spontaneous arousal, response to voice, touch, pain
- Tone: Passive tone (resistance to passive movement of limbs, head lag, ventral suspension, horizontal suspension — "floppy baby" sinks over hand). Active tone (spontaneous movements).
- Primitive reflexes: Suck, rooting, Moro, palmar/plantar grasp, tonic neck reflex
- Cranial nerves: Pupil size and reaction, extraocular movements ("doll's eye" reflex = oculocephalic reflex), corneal reflex, gag, facial movement
- Seizures: Subtle (lip smacking, eye deviation, pedalling), focal clonic, multifocal clonic, tonic, myoclonic
- Fontanelle: Bulging = raised ICP/cerebral oedema
- Respiratory pattern: Normal, periodic, Cheyne-Stokes, apnoea
- Deep tendon reflexes: Diminished in moderate/severe HIE
Neonatal seizures differ because the neonatal brain is immature — incomplete myelination prevents generalised tonic-clonic (GTC) spread. Clinical diagnosis is unreliable; EEG confirmation is essential.
Types of neonatal seizures (in order of frequency in HIE):
| Type | Description | Notes |
|---|---|---|
| Subtle | Eye deviation, lip smacking, chewing, pedalling, apnoea | Most common overall; easily missed |
| Focal Clonic | Rhythmic jerking of one limb or face | Common in HIE and focal ischaemia |
| Multifocal Clonic | Clonic movements migrating asynchronously | Typical of HIE |
| Tonic | Sustained posturing of limbs or trunk | Associated with severe HIE or IVH |
| Myoclonic | Single or repetitive sudden jerks | Worst prognosis |
💡 Remember
HIE is the most common cause of neonatal seizures in term infants. Seizures in HIE typically appear within the first 6–24 hours of life. "Subtle" seizures (autonomic/ocular/oral automatisms) are the most common type but often have NO EEG correlate — called electroclinical uncoupling.
- Stage 1 (Mild): Mydriasis (dilated) — sympathetic hyperactivation
- Stage 2 (Moderate): Miosis (constricted) but reactive — parasympathetic dominance
- Stage 3 (Severe): Fixed, poorly reactive pupils (mid-position or small) — brainstem dysfunction, loss of both sympathetic and parasympathetic control
Fixed, non-reactive pupils in HIE indicate severe brainstem injury and carry a very poor prognosis.
- Bulging, tense anterior fontanelle (most reliable early sign)
- Separated cranial sutures
- Sunset sign (downward deviation of eyes = "setting sun" appearance)
- Scalp vein distension
- Increasing head circumference
- Bradycardia, hypertension, irregular respiration (Cushing's triad — a late and ominous sign)
- Irritability, high-pitched cry → decreased consciousness
The pattern depends on the nature and duration of the insult:
| Insult Type | Brain Region Affected | Imaging Pattern |
|---|---|---|
| Acute profound (sudden total asphyxia) | Basal ganglia, thalami, perirolandic cortex (most metabolically active) | BG/thalamic injury pattern — worst prognosis for motor outcome |
| Partial prolonged (chronic partial) | Watershed zones — parasagittal cortex (between ACA/MCA, MCA/PCA territories) | Parasagittal injury — affects proximal limb function ("man in barrel" syndrome) |
| Combined/severe | Diffuse cortical and deep grey matter | Multicystic encephalomalacia, severe atrophy |
The Thompson Score (Thompson et al., 1997) is a numeric scoring system (0–22) based on 9 clinical parameters (tone, level of consciousness, seizures, posture, Moro, grasp, suck, respiration, fontanelle). Each is scored 0–3.
- Score ≤10 → Good prognosis
- Score ≥11–14 → Moderate risk
- Score ≥15 → Poor prognosis (high risk of death/disability)
Advantage over Sarnat: Serial scoring possible; monitors evolution of encephalopathy. Used widely in LMIC settings where EEG/MRI may not be available.
🔬 Investigations — Exam Q&A
Biochemical (to assess asphyxia severity and organ involvement):
- Cord blood or early neonatal arterial blood gas — pH, base deficit (key criterion: pH <7.0, BD ≥12–16 mEq/L)
- Blood glucose (exclude hypoglycaemia — maintain ≥45–50 mg/dL)
- Serum electrolytes (Na, K, Ca, Mg) — hyponatraemia from SIADH common
- Serum creatinine and urea (renal involvement)
- Liver function tests — AST, ALT, PT/aPTT, fibrinogen (hepatic/coagulopathy)
- CBC — anaemia, thrombocytopenia, polycythaemia
- Serum lactate — elevated in asphyxia
- Blood culture (to exclude sepsis as a cause)
- Cardiac enzymes — Troponin I (myocardial injury)
Urine output monitoring: A sensitive indicator of renal perfusion. Oliguria (<1 mL/kg/hr) = renal involvement.
aEEG (Amplitude-Integrated EEG) is a simplified, bedside, continuous 1- or 2-channel EEG monitoring tool. It provides a compressed, time-trend display of brain electrical activity.
Uses in HIE:
- Confirms encephalopathy severity (supports eligibility for cooling)
- Detects electrographic seizures — especially important since clinical diagnosis is unreliable (subtle/electroclinical dissociation)
- Monitors response to antiseizure medications
- Prognostication — background pattern normalisation by 24–48 h predicts better outcome
aEEG patterns (prognostic):
| Pattern | Description | Outcome |
|---|---|---|
| Normal (Continuous) | Upper margin >10 μV, lower >5 μV | Good |
| Discontinuous | Lower margin <5 μV, periodic activity | Moderate risk |
| Burst Suppression | Periodic high-voltage bursts with flat segments | Poor |
| Continuous Low Voltage | Upper margin <10 μV, lower <5 μV | Poor |
| Flat/Isoelectric | <2 μV throughout | Very poor |
- CUS is widely available and bedside-friendly
- In HIE, CUS may show increased echogenicity of the brain parenchyma ≥48 hours after injury (not sensitive in the first 24–48 hours)
- Primarily used to exclude other causes of NE: intracranial haemorrhage (IVH, subdural), periventricular leukomalacia (PVL in preterm), congenital anomalies
- Can show cerebral oedema (sulcal effacement, slit-like ventricles)
- Limitation: Poor sensitivity and specificity for HIE compared to MRI; cannot assess posterior fossa or cortical injury well
MRI brain (with DWI — Diffusion Weighted Imaging) is the gold standard.
- Optimal timing: Day 3–5 (24–96 hours after insult — DWI most sensitive at this time)
- A second MRI at 10–14 days (or later) better delineates the final extent of injury as DWI changes "pseudo-normalise" by day 7–10
- DWI: Shows restricted diffusion (bright signal) in areas of acute ischaemia — most sensitive early
- T1/T2: Shows basal ganglia/thalamic signal abnormalities, cortical laminar necrosis, haemorrhage
- MR Spectroscopy: Shows ↑ lactate peak and ↓ NAA (N-acetyl aspartate) peak — confirms ongoing metabolic injury and has prognostic value
💡 DWI pseudo-normalisation
DWI signal can become falsely normal by day 7–10 even though injury is severe — this is "pseudo-normalisation." A late MRI (Day 10–14) using T1/T2 is more reliable for final injury assessment and prognostication.
- Cord blood lactate: >9 mmol/L associated with poor outcome
- Cord blood pH and base deficit: Established biochemical criteria
- NSE (Neuron-Specific Enolase): Released from injured neurons — elevated in severe HIE
- S100β protein: Astrocyte injury marker — elevated levels correlate with severity
- GFAP (Glial Fibrillary Acidic Protein): Emerging blood/CSF biomarker of glial injury
- Cord blood AST: Correlates well with HIE severity; widely available in LMIC
- Serum Lactate Dehydrogenase (LDH): Elevated in multi-organ dysfunction
Currently, no single biomarker is validated for routine clinical decision-making in HIE diagnosis or prognosis.
| Parameter | Target | Rationale |
|---|---|---|
| Blood glucose | 45–120 mg/dL (avoid hypoglycaemia AND hyperglycaemia) | Both worsen brain injury |
| SpO2 | 94–99% (avoid hyperoxia) | Free radical injury |
| PaCO2 | 45–55 mmHg (avoid hypo- and hypercapnia) | Affects cerebral blood flow |
| Blood pressure | MAP >40–45 mmHg (adequate perfusion) | Cerebral autoregulation impaired |
| Temperature | 33–34°C (during TH); avoid hyperthermia post-TH | Fever worsens secondary injury |
| Sodium | 135–145 mEq/L | SIADH causes hyponatraemia |
| Calcium | Correct hypocalcaemia | May trigger seizures |
💊 Management — Exam Q&A
Follow the Neonatal Resuscitation Program (NRP) / Neonatal Life Support (NLS) algorithm:
- Initial steps (golden minute): Warm, dry, stimulate, clear airway (only if obstructed), pulse oximetry
- Assess: Breathing/crying? HR? Tone?
- If apnoeic or HR <100: Start Positive Pressure Ventilation (PPV) with room air (21% O2 for term infants) at 40–60 breaths/min
- If HR <60 after 30 sec of adequate PPV: Begin chest compressions (3:1 ratio with PPV)
- If HR remains <60: IV/IO Adrenaline (0.01–0.03 mg/kg = 0.1–0.3 mL/kg of 1:10,000)
- Volume expansion if blood loss suspected: Normal saline 10 mL/kg IV over 5–10 min
- Avoid hyperoxia: Titrate O2 by SpO2; start with room air for term infants
🚨 Key Point — Avoid Hyperoxia
100% O2 during neonatal resuscitation worsens outcome due to increased free radical generation. Term infants are resuscitated with 21% O2 (room air) initially, titrated to SpO2 targets.
TH is the ONLY evidence-based neuroprotective treatment for HIE. It exploits the latent phase between primary and secondary energy failure.
Eligibility Criteria (ALL must be met):
- Gestational age ≥36 weeks
- Birth weight ≥1800 g
- Age ≤6 hours (initiated within 6 hours of birth)
- Evidence of perinatal hypoxia: Cord pH <7.0 OR Base Deficit ≥12–16 mEq/L OR Apgar ≤5 at 10 min OR need for resuscitation at 10 min
- Evidence of moderate or severe encephalopathy (Sarnat Stage 2 or 3) — assessed on neurological exam or aEEG
Protocol:
- Target temperature: 33–34°C (33.5°C) rectal/oesophageal temperature
- Duration: 72 hours
- Rewarming: 0.5°C per hour (slow rewarming over 6–12 hours; rapid rewarming can cause rebound seizures)
- Methods: Whole body cooling (cooling blanket — preferred) OR Selective head cooling (with mild systemic hypothermia)
Mechanism: ↓ metabolic rate → ↓ glutamate release → ↓ excitotoxicity → ↓ free radical production → ↓ inflammation and apoptosis cascade → ↓ secondary energy failure.
✅ Evidence
TH reduces the combined outcome of death or major neurodevelopmental disability by ~25% in moderate HIE. NNT = 6–7 for moderate HIE. Less effective for severe HIE but still beneficial vs. no treatment.
- Bradycardia: Expected; HR 80–100 at 33.5°C (HR ↓ ~15 bpm per °C ↓). Only treat if HR <60 with haemodynamic compromise.
- QTc prolongation: ECG monitoring required
- Hypotension: Reduced cardiac output; maintain MAP >40–45 mmHg with volume/vasopressors
- Coagulopathy/Thrombocytopenia: Hypothermia impairs platelet function and clotting cascade
- Hypoglycaemia: Altered glucose metabolism; monitor closely
- Electrolyte disturbances: Hypokalaemia, hypocalcaemia
- Pulmonary hypertension (PPHN) — may worsen
- Subcutaneous fat necrosis: Firm, erythematous skin nodules (especially buttocks/back); can cause hypercalcaemia
- Feeding intolerance: Gut motility reduced; delay full feeds during cooling
- Rebound seizures during rewarming if rewarmed too rapidly
- Airway/Breathing: Mechanical ventilation if apnoeic or respiratory failure; avoid hyperoxia (SpO2 94–99%); avoid hypo/hypercapnia (PaCO2 40–55 mmHg)
- Circulation: Maintain MAP >40–45 mmHg; judicious fluid management (restrict to 60–80 mL/kg/day if oliguria/SIADH; avoid fluid overload); vasopressors (dopamine, dobutamine) if hypotension refractory
- Glucose: Maintain 45–120 mg/dL; dextrose infusion (GIR 4–6 mg/kg/min initially); avoid hypoglycaemia AND hyperglycaemia
- Seizure management: Phenobarbital (first line, 20 mg/kg IV loading dose); second line — Levetiracetam (40–60 mg/kg IV) or Phenytoin/Fosphenytoin (20 mg PE/kg); Midazolam infusion for refractory seizures
- Nutrition: NPO or minimal enteral feeds during cooling (gut motility reduced, NEC risk); parenteral nutrition; resume full enteral feeds after rewarming
- Avoid hyperthermia: Even mild temperature elevation (>37°C) worsens outcome — a key and easily addressable factor
- Monitor for multi-organ dysfunction and treat accordingly
Step 1 — Treat the cause: Correct hypoglycaemia, hypocalcaemia, hypomagnesaemia before starting antiseizure drugs.
Step 2 — Antiseizure medications:
- First line — Phenobarbital: Loading dose 20 mg/kg IV slowly. If seizures persist, give additional 5–10 mg/kg boluses (max 40 mg/kg). Maintenance: 3–5 mg/kg/day in 1–2 divided doses.
- Second line — Levetiracetam: 40–60 mg/kg IV (gaining favour due to fewer respiratory side effects)
- Second line — Phenytoin/Fosphenytoin: 20 mg PE/kg IV (monitor for cardiac arrhythmia)
- Third line (refractory seizures) — Midazolam infusion: 0.1–0.4 mg/kg/hr IV; or Lidocaine infusion
- Do not use prophylactic antiseizure drugs in HIE without EEG-confirmed seizures
💡 Important
EEG confirmation of seizures is essential before adding second-line agents, due to the phenomenon of electroclinical uncoupling — clinical movements may stop while electrographic seizures persist.
| HIE Stage | Mortality | Neurological Sequelae in Survivors |
|---|---|---|
| Stage 1 (Mild) | Minimal | Normal outcome in most; subtle learning difficulties possible |
| Stage 2 (Moderate) | ~10–20% | 20–35% have neurological deficits (with TH, risk reduced by ~25%) |
| Stage 3 (Severe) | ~50–75% | ~80% of survivors have severe neurological sequelae |
Long-term sequelae include:
- Cerebral palsy (most common — especially spastic quadriplegia)
- Epilepsy (20–30% of moderate-severe HIE survivors)
- Intellectual disability, developmental delay
- Cortical visual impairment, sensorineural hearing loss
- Autism spectrum disorder, ADHD
- Learning difficulties, behavioural problems
Poor prognostic indicators: Sarnat Stage 3, flat/burst-suppression aEEG, bilateral BG/thalamic injury on MRI, need for CPR at delivery, prolonged seizures, Apgar 0 at 10 min.
Passive cooling means turning off the radiant warmer and removing blankets to allow the baby's temperature to drift naturally toward the target (33–34°C), without active cooling devices. It is used:
- When a baby meets TH criteria but no servo-controlled cooling device is available
- During transport to a TH centre
- In resource-limited settings
Risks of passive cooling: Unpredictable temperature — risk of overcooling (<33°C) or undercooling (>34°C). Core temperature must be monitored continuously (rectal probe). Servo-controlled active cooling is always preferred when available.
- Repeat MRI at 4–6 weeks (or Day 10–14 before discharge) to assess final injury extent
- Visual evoked potentials (VEP) and brainstem auditory evoked responses (BAER/ABR)
- Hearing test (BERA) — higher risk of sensorineural hearing loss
- Regular developmental surveillance: Griffiths/Bayley scales of development
- Neurological follow-up at 3, 6, 12, 18, 24 months and beyond
- EEG if epilepsy suspected
- Physiotherapy, speech therapy, occupational therapy as needed
- Ophthalmology assessment (cortical visual impairment)
🔭 Recent Advances — Exam Q&A
Erythropoietin (EPO) and its analogue Darbepoetin are known erythropoietic hormones that also have neuroprotective properties:
- Reduces apoptosis, excitotoxicity, and inflammation in the injured brain
- Promotes neurogenesis and angiogenesis
The HEAL Trial (High-dose Erythropoietin for Asphyxia and Encephalopathy) — a large, multicentre RCT (2022) — studied high-dose EPO (1000 U/kg IV × 6 doses) as adjunct to TH in moderate-severe HIE. Unfortunately, it did NOT show a reduction in death or neurodevelopmental impairment at 2 years. EPO is not currently recommended for clinical use in HIE outside trials.
Melatonin is a potent antioxidant and anti-inflammatory agent that crosses the blood-brain barrier freely. In animal models of HIE, it reduces oxidative stress and secondary neuronal death.
- Small clinical trials have shown promising results as an adjunct to TH
- Currently under investigation in RCTs (e.g., MELPAS trial)
- Advantages: Safe, cheap, widely available, oral/IV administration
- Status: Not yet recommended for routine clinical use — awaiting large RCT data
Stem cells — particularly umbilical cord blood (UCB) derived stem cells and mesenchymal stem cells (MSCs) — are being studied as neuroprotective and neurorestorative agents in HIE.
- Proposed mechanisms: Immunomodulation, trophic factor release, anti-apoptosis, neurogenesis promotion
- Small Phase I/II trials show safety and some signal of efficacy
- The COMET trial (Cord blood and Melatonin) is an example of ongoing trials
- Autologous UCB cells (collected at birth and transfused back) are in trials
- Status: Experimental; not yet standard of care
Xenon is a noble gas with NMDA receptor antagonist properties — blocking glutamate-mediated excitotoxicity. In animal models, inhaled Xenon combined with TH was highly neuroprotective.
- The TOBY-Xe trial (UK, 2016) — Phase II trial of inhaled 50% Xenon for 24 hours + TH vs TH alone — showed no significant improvement in MRI injury or clinical outcomes
- Xenon is expensive, rare, and requires specialised delivery equipment
- Status: Not recommended for clinical use based on current evidence
- Continuous video-EEG is becoming standard in high-resource settings for all neonates with moderate-severe HIE
- Machine learning algorithms are being developed for automated seizure detection on aEEG/EEG — increasing accuracy and reducing reliance on expert interpretation
- qEEG (Quantitative EEG): Automated analysis of EEG features (power spectrum, burst suppression ratio) for real-time prognostication
- Goal: To identify which neonates have ongoing electrographic seizures (that are clinically silent) and respond to treatment — guided by EEG rather than clinical observation alone
Mild HIE (Sarnat Stage 1) was historically thought to have a uniformly good prognosis; however, studies have shown that up to 20–25% of infants with mild HIE have abnormal MRI and ~15% develop neurodevelopmental impairment.
- There is growing debate about extending TH to mild HIE
- The LIFT Trial (Low-grade Therapeutic Hypothermia for Infants with Mild Encephalopathy) and other trials are investigating this
- Currently, TH for mild HIE is NOT recommended outside of clinical trials (AAP 2025 guideline)
- Key concern: Risk of overcooling, coagulopathy, and pulmonary hypertension must outweigh uncertain benefit
⚡ Key Points — Quick Revision
One-Liners for Exam
- Definition: HIE = disturbed neurological function in neonate ≥35 weeks due to perinatal hypoxia-ischaemia
- Incidence: 1.5–2.5/1000 live births (developed); up to 30/1000 (developing world)
- Most common cause of neonatal seizures: HIE (in term infants)
- Pathophysiology: Primary energy failure → Latent phase (therapeutic window 1–6 hrs) → Secondary energy failure
- Staging: Modified Sarnat — Stage 1 (Mild: hyperalert, mydriasis), Stage 2 (Moderate: obtunded, miosis, seizures), Stage 3 (Severe: coma, flaccid, fixed pupils)
- Gold standard investigation: MRI brain with DWI (Day 3–5 optimal; repeat Day 10–14)
- Bedside brain monitoring: Amplitude-integrated EEG (aEEG)
- Only evidence-based treatment: Therapeutic Hypothermia — 33–34°C for 72 hours, initiated ≤6 hours of birth, for Stage 2 & 3, ≥36 weeks GA
- Rewarming: 0.5°C per hour (never rapid — causes rebound seizures)
- First-line antiseizure drug: Phenobarbital 20 mg/kg IV loading dose
- Avoid in resuscitation: 100% O2 (use room air — 21%); also avoid hyperthermia post-birth
- Multi-organ involvement: Kidneys (most after brain), heart, liver, lungs, gut
- Passive cooling: Turn off warmer — used in transport or resource-limited settings
- TH contraindicated: <35–36 weeks GA, major congenital anomalies, birth weight <1800 g, severe coagulopathy (relative), if age >6 hours (though 6–24 h considered case-by-case)
- Best prognostic tool: MRI Day 10–14 + aEEG background normalisation
- Main long-term sequelae: Cerebral palsy, epilepsy, intellectual disability, hearing/visual impairment
- Stage 1 outcome: Normal in most | Stage 2 outcome (with TH): ~25% disability | Stage 3 outcome: 50–75% mortality; ~80% disability in survivors
💡 High-Yield Exam Mnemonics
- "ABCDE of HIE management": Airway (ventilation), Blood sugar (45–120), Cooling (TH), Drugs (Phenobarbital for seizures), Electrolytes/Evaluation (MRI/aEEG)
- Sarnat pupils: Stage 1 = Dilated (D-1), Stage 2 = Constricted (C-2), Stage 3 = Fixed (F-3)
- TH rule of 3s: Target 33°C, for 72 hours (3 days), within 6 hours (<3 × 2 hours), for Stage 2–3