Therapeutic Hypothermia for Neonatal Encephalopathy
A gestational age of 36 weeks is usually the minimum age required for TH. Cooling of younger infants has not been studied on a large scale; however, some institutions have expanded the eligibility down to 34 weeks gestational age. Additionally, the therapeutic window for hypothermia ends at 6 hours of age and it is believed that implementation after that time does not yield the same level of protection. Therefore, the infant must be less than 6 hours old. General exclusions include presence of major congenital anomalies or weight less than 1800 grams. Then, a combination of clinical findings, lab results, and neurological examination is used to diagnose NE. Some institutions may also use amplitude-integrated electroencephalography (aEEG) to identify cooling candidates.
Clinical findings that indicate NE include history of an acute perinatal event such as cord prolapse or placental abruption, Apgar ≤ 5 at 5 or 10 minutes, and continued need for resuscitation or ventilator support after delivery. Lab results indicative of increased risk for NE include cord blood or postnatal blood gas pH of ≤ 7.0 at ≤ 1 hour of life or base deficit ≥ 16 mEq/L at ≤ 1 hour of life. Neurological status is assessed using the modified Sarnat score and infants are categorized as mild, moderate, or severe if they present with 3 of the 6 indicators for a stage. Generally, only infants with moderate to severe NE will be cooled. A decision tree adapted from the NICHD NRN Whole Body Hypothermia trial combining all eligibility criteria for cooling is provided in Table 2 .
Who Should Be Cooled?
A gestational age of 36 weeks is usually the minimum age required for TH. Cooling of younger infants has not been studied on a large scale; however, some institutions have expanded the eligibility down to 34 weeks gestational age. Additionally, the therapeutic window for hypothermia ends at 6 hours of age and it is believed that implementation after that time does not yield the same level of protection. Therefore, the infant must be less than 6 hours old. General exclusions include presence of major congenital anomalies or weight less than 1800 grams. Then, a combination of clinical findings, lab results, and neurological examination is used to diagnose NE. Some institutions may also use amplitude-integrated electroencephalography (aEEG) to identify cooling candidates.
Clinical findings that indicate NE include history of an acute perinatal event such as cord prolapse or placental abruption, Apgar ≤ 5 at 5 or 10 minutes, and continued need for resuscitation or ventilator support after delivery. Lab results indicative of increased risk for NE include cord blood or postnatal blood gas pH of ≤ 7.0 at ≤ 1 hour of life or base deficit ≥ 16 mEq/L at ≤ 1 hour of life. Neurological status is assessed using the modified Sarnat score and infants are categorized as mild, moderate, or severe if they present with 3 of the 6 indicators for a stage. Generally, only infants with moderate to severe NE will be cooled. A decision tree adapted from the NICHD NRN Whole Body Hypothermia trial combining all eligibility criteria for cooling is provided in Table 2 .