Hypoxic ischemic encephalopathy (HIE) is a significant cause of mortality and long-term disability in late preterm and term infants. The risk of disability and cognitive impairment is correlated with the severity of HIE. The idea that mild cooling might be beneficial in these circumstances to decrease mortality and long term neurodevelopmental disabilities has been considered by clinicians for many years.
Hypoxic ischemic encephalopathy (HIE) is a condition — generally described as mild, moderate or severe — that occurs when the brain is deprived of an adequate supply of oxygen. The time of oxygen loss or deprivation generally relates to the perinatal period, just before, during and shortly after delivery. HIE may be manifested by a reduced or abnormal level of consciousness (hyper alert, irritable, lethargic), seizures, diminished spontaneous movement, difficulty with breathing and feeding, and reduced tone and abnormal reflexes. Upon delivery, the infant may exhibit low APGAR scores, a weak or absent cry and a failure to establish spontaneous respirations.
Cooling as Treatment for HIE
Clinical studies in the early 2000s started with a consensus on the science of HIE and the effects of cooling. According to a study published in the Journal of Resuscitation in 2008, “A reduction of body temperature by 2-3 degrees C (which constitutes modest hypothermia) following a hypoxic-ischemic event has the effect of reducing cerebral metabolic and biochemical abnormalities and cerebral injury.”
Neonatal therapeutic hypothermia is a relatively new treatment option in which an infant’s total body temperature is reduced shortly after birth in order to reduce the chances of severe brain damage and slow down disease progression. According to the National Institute of Health, there are quite a few long term benefits to neonatal therapeutic hypothermia. For instance, children who underwent treatment as infants were more likely to have a higher survival rate at 6-7 years of age.
Criteria for Cooling Therapy as Treatment
Infants who are at or greater than 36 weeks gestation and who meet the necessary criteria should be “offered” hypothermia. Active cooling can be accomplished by selectively cooling the infant’s head with cooling caps or total body cooling with cold packs or cooling blankets. Careful management of rectal or esophageal body temperature at an optimal range of 34 degrees C, plus or minus 0.5 degrees C, is important.
Optimal duration of treatment was not initially clear, but most practitioners used 72 hours of cooling. At the same time, “re-warming” of the neonate is not without controversy, and care needs to be taken to slowly restore body temperature. Worsening of encephalopathy and seizures have occurred on rewarming, and may require re-cooling of the infant. Subsequent studies on the therapeutic effects of controlled hypothermia for infants presenting with symptoms of HIE continues to support the therapy as part of the applicable standard of care.
Click here for the full Neonatal Practice Guidelines- Hypothermia for Newborns With Hypoxic Ischemic Encephalopathy
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