Neonatal hypoxic-ischemic encephalopathy

Neurology

Neonatal hypoxic–ischaemic encephalopathy (HIE) is a serious neurological condition caused by impaired oxygen delivery and blood flow to the brain around the time of birth. It occurs predominantly in term and late-preterm infants and is an important cause of neonatal mortality and long-term neurodevelopmental disability worldwide. The severity of brain injury varies, with affected infants potentially developing outcomes ranging from minimal impairment to significant neurological disability, including cerebral palsy, cognitive and developmental difficulties, epilepsy, and sensory deficits. Early recognition and prompt assessment are essential to establish the severity of encephalopathy, identify eligible infants for therapeutic hypothermia, and initiate supportive management within the appropriate therapeutic window. Effective care requires close monitoring, careful management of associated organ dysfunction, and coordinated multidisciplinary follow-up to identify developmental difficulties and provide timely intervention. A structured, time-sensitive approach is therefore essential to minimise secondary brain injury and improve outcomes for infants affected by HIE.[1]Pathophysiology and clinical presentationHIE develops when impaired cerebral oxygenation and perfusion disrupt cellular energy production, leading to metabolic failure, excitotoxicity, oxidative stress, inflammation, and neuronal injuryThe severity of injury depends on the intensity and duration of the insult, the infant’s physiological response, and the effectiveness of subsequent resuscitation and supportive careClinical manifestations may include altered consciousness, abnormal muscle tone, impaired primitive reflexes, respiratory depression, feeding difficulties, and seizuresEncephalopathy may evolve over the first hours after birth, so serial neurological examinations are important when initial findings are inconclusiveDiagnosis and severity assessmentThe assessment should incorporate the perinatal history, evidence of impaired gas exchange, resuscitation requirements, neurological examination, and relevant laboratory findingsUmbilical cord or early neonatal blood gas analysis may demonstrate metabolic acidosis, although results must be interpreted alongside the clinical presentation and timing of samplingStandardized neurological examinations help classify encephalopathy as mild, moderate, or severe and support decisions about eligibility for therapeutic hypothermiaAmplitude-integrated electroencephalography or conventional electroencephalography can help identify seizures and characterize cerebral electrical activityBrain magnetic resonance imaging is useful for defining the pattern and extent of injury, with timing determined by the infant’s clinical condition and local protocolsAcute management and neuroprotectionInitial management prioritizes effective ventilation, oxygenation, circulation, temperature control, and correction of clinically significant metabolic disturbances while avoiding further physiological injuryTherapeutic hypothermia is the established neuroprotective treatment for eligible infants with moderate-to-severe HIE when initiated within the recommended early treatment window, generally within six hours after birthCooling is usually maintained at a controlled target temperature for 72 hours, followed by gradual rewarming under continuous clinical monitoring and according to an established protocolSeizures should be identified promptly using electroencephalographic monitoring when available and treated according to neonatal seizure protocolsSupportive care includes monitoring glucose, electrolytes, renal and hepatic function, coagulation, fluid balance, and cardiorespiratory statusComplications and follow-upAcute complications may include seizures, pulmonary hypertension, myocardial dysfunction, kidney injury, hepatic dysfunction, coagulopathy, and feeding intoleranceInfants with HIE require structured neurodevelopmental follow-up because motor, cognitive, language, behavioral, hearing, or visual difficulties may emerge over timeEarly referral for developmental assessment and appropriate rehabilitation can help address emerging impairments and support familiesClinical considerations during managementClinical concernPractical considerationTransport to a specialist centerEarly consultation and coordinated transfer can help eligible infants receive timely assessment and cooling.Temperature monitoringContinuous, reliable core-temperature monitoring is essential during cooling and rewarming.Family communicationClear, compassionate discussions should address clinical uncertainty, treatment goals, potential outcomes, and opportunities for family involvement.Long-term planningFollow-up arrangements should be established before discharge and tailored to neurological findings and developmental risk.ConclusionNE in term and near-term infants is characterised by altered neurological function, including changes in consciousness, tone, and reflexes. As a clinical syndrome rather than a diagnosis of a specific cause, NE may result from hypoxic–ischaemic injury, infection, intracranial haemorrhage, stroke, brain malformations, metabolic disorders, genetic conditions, or a combination of factors. HIE is an important cause and requires prompt recognition, careful neurological assessment, and coordinated neonatal intensive care to limit secondary brain injury and manage associated complications. Therapeutic hypothermia should be initiated within the recommended treatment window in eligible infants, alongside appropriate supportive care and close monitoring. As neurological outcomes vary and developmental difficulties may emerge over time, structured follow-up, developmental surveillance, and timely intervention are essential components of ongoing care to support the best possible long-term outcomes.[2]Reference(s):1. Arnautovic T, Sinha S, Laptook AR. Neonatal Hypoxic-Ischemic Encephalopathy and Hypothermia Treatment. Obstet Gynecol. 2024;143(1):67-81. doi:10.1097/AOG.0000000000005392. https://pmc.ncbi.nlm.nih.gov/articles/PMC10841232/2. Chakkarapani E, de Vries LS, Ferriero DM, Gunn AJ. Neonatal encephalopathy and hypoxic-ischemic encephalopathy: the state of the art. Pediatr Res. 2025;98(7):2444-2458. doi:10.1038/s41390-025-03986-2. https://pmc.ncbi.nlm.nih.gov/articles/PMC12875882/