Hypoxic Ischemic Encephalopathy (HIE) & Neonatal Seizures - High-Yield Viva Questions
| Question | Answer / Practical Pearls |
|---|---|
| What are the mandatory criteria to diagnose Perinatal Asphyxial Hypoxic-Ischemic Encephalopathy (AAP / ACOG)? | 1. Umbilical cord arterial blood gas acidemia: $\text{pH} < 7.00$ or Base Deficit $\ge 12-16\text{ mmol/L}$. 2. Apgar score: $\le 5$ at 5 minutes and 10 minutes. 3. Neonatal Encephalopathy: Moderate or severe neurological dysfunction (Modified Sarnat Stage II or III). 4. Multisystem organ involvement: Acute kidney injury, elevated transaminases, myocardial dysfunction, or pulmonary hypertension. VIVA TRAP: 'Birth Asphyxia' is an imprecise, medicolegally fraught term. Always use 'Neonatal Encephalopathy attributed to intrapartum hypoxia-ischemia'. |
| Differentiate Modified Sarnat Stages 1, 2, and 3. | • Stage 1 (Mild): Hyperalert, irritable, tachycardia, dilated pupils, brisk Moro reflex, normal muscle tone. NO clinical seizures. Duration $<24$ hours. $>98\%$ normal neurodevelopmental outcome. • Stage 2 (Moderate): Lethargic/obtunded, generalized hypotonia, miosis, suppressed primitive reflexes, Frequent clinical seizures. Duration 2-14 days. 20-30% mortality or neurodevelopmental disability. • Stage 3 (Severe): Stupor/coma, flaccid, brainstem dysfunction (apnea, unequal fixed dilated pupils), absent primitive reflexes, refractory seizures or electrocerebral silence. 50-75% mortality, severe spastic quadriplegia in survivors. |
| What are the precise eligibility criteria, target temperature, and duration for Therapeutic Hypothermia? | • Eligibility Criteria: - Gestation $\ge 35\text{ completed weeks}$ AND birth weight $\ge 1800\text{ grams}$. - Initiated strictly within 6 hours of life (the therapeutic window prior to secondary energy failure). - Physiological evidence of asphyxia (cord pH $\le 7.00$ or BD $\ge 16\text{ mmol/L}$, or acute event + 10-min Apgar $\le 5$). - Evidence of Moderate to Severe encephalopathy (Sarnat Stage II/III) or abnormal aEEG background. • Target Temperature: Core rectal temperature $33.5^\circ\text{C} \pm 0.5^\circ\text{C}$ maintained continuously for 72 hours. • Rewarming Protocol: Controlled, slow rewarming at $0.5^\circ\text{C}\text{ every 2 hours}$ over 10-12 hours until $36.5^\circ\text{C}$ is reached. VIVA TRAP: Rapid rewarming causes severe peripheral vasodilation, profound hypotension, and rebound neonatal seizures! |
| How do you distinguish neonatal jitteriness from true epileptic seizures at the bedside? | 1. Gaze Abnormalities: Jitteriness does not have abnormal eye movements (tonic deviation, nystagmus); seizures typically exhibit abnormal ocular movements. 2. Stimulus Sensitivity: Jitteriness is provoked by tactile or auditory stimulation and stops immediately upon gentle passive limb flexion or holding. True seizures cannot be aborted by holding the limb. 3. Movement Character: Jitteriness consists of rapid, alternating equal tremor movements; clonic seizures have a distinct fast contraction phase followed by a slow relaxation phase. 4. Autonomic Changes: Seizures often have tachycardia, hypertension, or desaturations; jitteriness does not. |
| What is the first-line and second-line antiseizure medication algorithm for neonatal seizures? | • First-Line Drug: Phenobarbital (Phenobarbitone) at $20\text{ mg/kg IV}$ infused over 20 minutes. If seizures continue, repeat boluses of $10-20\text{ mg/kg}$ up to a cumulative maximum of $40\text{ mg/kg}$. • Second-Line Options: If seizures persist despite $40\text{ mg/kg}$ Phenobarbital: - Levetiracetam: $40-60\text{ mg/kg IV}$ bolus over 10 minutes. - Or Fosphenytoin: $20\text{ mg PE/kg IV}$ under ECG monitoring. - Or Midazolam infusion: $0.15\text{ mg/kg}$ bolus followed by $1-4\text{ mcg/kg/min}$. • Refractory Seizures: Administer a diagnostic therapeutic trial of $100\text{ mg IV Pyridoxine}$ under continuous EEG/ECG monitoring to rule out pyridoxine-dependent epilepsy. |
| What is the optimal timing for Brain MRI in neonatal HIE, and what is the significance of the 'Loss of PLIC Sign'? | • Optimal Timing: Between Day 4 and Day 7 of life (post-rewarming). DWI is sensitive from day 2-4; conventional T1/T2 imaging is most informative between days 4 and 7. • Posterior Limb of Internal Capsule (PLIC): In normal term neonates, the PLIC demonstrates high T1 signal intensity (hyperintense) due to advanced physiological myelination. • 'Loss of PLIC Sign': Disappearance of this normal hyperintensity (appears isointense or hypointense) indicates severe hypoxic-ischemic motor tract injury and is the single strongest neuroimaging predictor of bilateral spastic cerebral palsy! |