Hypoxic-ischaemic brain injury: Viva

Branch 1: Classification and the principle of secondary injury

The candidate should classify hypoxic-ischaemic brain injury in the infant and child beyond the neonatal period as global brain injury from a cardiorespiratory arrest or asphyxial event, and should separate it from neonatal hypoxic-ischaemic encephalopathy. A strong candidate states that the injury divides into a primary injury, the neuronal death at the moment of arrest that is already fixed, and a secondary injury, the reperfusion cascade over hours to days that intensive care targets, and that this temporal classification drives the entire management because every intervention aims at a specific element of the secondary cascade. [7]

If the examiner presses on the biology, the candidate should describe the energy-failure cascade: ATP depletion, pump failure, cytotoxic oedema, glutamate release, and calcium influx producing rapid neuronal death, followed after reperfusion by mitochondrial dysfunction, oxidative stress, inflammation, and apoptosis. The candidate should explain that this is why cooling works, because it reduces metabolic demand, suppresses excitotoxicity, dampens inflammation, and limits apoptotic cascades. [1][7]

Branch 2: Targeted temperature management and the THAPCA trials

If asked what temperature target to use for this drowned child, the candidate should state that, for a comatose child after an out-of-hospital arrest, targeted temperature management at 32 to 34 degrees Celsius for 48 hours is a reasonable and guideline-supported option, with rewarming at no more than 0.5 degrees Celsius per hour. The candidate should cite the THAPCA out-of-hospital trial of Moler and colleagues, which compared hypothermia at 33 degrees with normothermia at 36.8 degrees in 295 children and found a non-significant trend favouring hypothermia, with good functional outcome at one year of 20 percent against 12 percent. [1]

If the examiner asks why the answer would differ for an in-hospital arrest, the candidate should describe the THAPCA in-hospital trial, which was stopped for futility after 329 children at 36 percent good outcome with hypothermia against 39 percent with normothermia, and should state that the standard after in-hospital arrest is therefore normothermia at 36 to 37.5 degrees with active fever prevention. If the examiner presses on the apparent tension between the non-significant out-of-hospital result and the choice to cool, the candidate should cite the Bayesian reanalysis by Harhay and colleagues, which concluded that there is a high probability that hypothermia provides a modest benefit, and should state that the 2020 American Heart Association guidelines accept both options while making fever prevention a clear priority. [2][3][7]

Branch 3: Neurocritical care and the pitfalls

If asked to describe the neurocritical care bundle, the candidate should give the targets of normoxia, normocapnia, normotension, normoglycaemia, and normothermia, with continuous EEG for non-convulsive seizures. A strong candidate explains the pitfalls: allowing hyperoxia or hyperventilation, because hyperoxia drives oxidative stress and hypocapnia constricts the cerebral vessels and worsens ischaemia; accepting hypotension in the early post-arrest window, because Topjian and colleagues showed that early postresuscitation hypotension is strongly associated with worse survival; and failing to detect and treat non-convulsive seizures, which affect up to half of comatose post-arrest children and are invisible to the bedside examination. [7]

If the examiner asks about prognostication, the candidate should state that it is multimodal and deferred to at least 72 hours, and not before sedation has cleared, combining the motor response, the brainstem reflexes, the continuous EEG background, the neuroimaging, and the biomarkers, with no single predictor sufficient. The candidate should name the communication pitfall of offering a definitive prognosis in the first days when the data are genuinely uncertain, and should model a family discussion that commits to a timeline for the formal prognostication rather than offering an early, unreliable prediction. [7]