What are the long-term sequelae and mortality rate for hypoxic-ischemic encephalopathy (HIE)?

Updated: Jul 18, 2018
  • Author: Santina A Zanelli, MD; Chief Editor: Dharmendra J Nimavat, MD, FAAP  more...
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In severe HIE, the mortality rate is reportedly 25-50%. Most deaths occur in the first days after birth due to multiple organ failure or redirection of care to comfort measures as a result of the grim prognosis. Some infants with severe neurologic disabilities die in their infancy from aspiration pneumonia or systemic infections.

The incidence of long-term complications depends on the severity of HIE. As many as 80% of infants who survive severe HIE develop serious complications, 10-20% develop moderately serious disabilities, and as many as 10% are healthy. Among the infants who survive moderately severe HIE, 30-50% may have serious long-term complications, and 10-20% have minor neurologic morbidities. Infants with mild HIE tend to be free from serious CNS complications.

Two therapeutic hypothermia trials provided updated information on mortality and the incidence of abnormal neurodevelopmental outcomes infants with moderate to severe HIE. [27, 28] In these trials, 23-27% of infants died prior to discharge from the neonatal intensive care unit (NICU), whereas the mortality rate at follow-up 18-22 months later was 37-38%. In these trials, neurodevelopmental outcomes at 18 months were as follows:

  • Mental development index (MDI): Scores of 85 or higher, 40%; 70-84, 21%; less than 70, 39%

  • Psychomotor development index (PDI): Scores of 85 or higher, 55%; 70-84, 10%; less than 70, 35-41%

  • Disabling cerebral palsy - 30%

  • Epilepsy - 16%

  • Blindness - 14-17%

  • Severe hearing impairment - 6%

Data from a randomized controlled trial was evaluated to determine the relationship between hypocarbia and the outcome for neonatal patients with hypoxic-ischemic encephalopathy. The results found that a poor outcome (death/disability at 18-22 mo) was associated with a minimum partial pressure of carbon dioxide (PCO2) and cumulative PCO2 of less than 35 mm Hg; death and disability increased with greater exposure to PCO2 of less than 35 mm Hg. [29]

Even in the absence of obvious neurologic deficits in the newborn period, long-term functional impairments may be present. In a cohort of school-aged children with a history of moderately severe HIE, 15-20% had significant learning difficulties, even in the absence of obvious signs of brain injury. Thus, all children who have moderate or severe HIE should be monitored well into school age. [30, 31, 32]

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