Diagnosis and Treatment for Early Hypoxic-Ischemic Encephalopathy
It is well established that forced hypothermia of a newborn infant with moderate to severe hypoxic-ischemic encephalopathy (HIE) is the standard of care. The earlier the hypothermia is begun, the better the outcome. This includes cooling the newborn with ice packs (ICE Trial) while awaiting transport to referral centers which have advanced technologies, such as neonatal intensive care units (NICU). It is important that educational programs about the ICE trial are maintained in these referring facilities so that the proper method of the application of ice packs is conducted. The goal is to lower the baby's body temperature 3-4 degrees C below baseline as quickly as possible after birth and definitely before 6 hours have passed. Based on studies, this should only be done if the baby is 36 weeks gestation or beyond, although some studies advocate it be done at earlier gestational ages if the birth weight is 1.8-2.0 kilograms which is approximately 4 to 4.4 pounds or more.
Get A 100% Free CASE EvaluationDiagnostic Criteria for Moderate to Severe HIE
The criteria for HIE were established in the studies that evaluated hypothermia.
They were –
- an Apgar score of 5 or more after 10 minutes
- respiratory support by ventilation for 10 minutes or more
- severe acidosis (very low blood pH of less than 7.0) found within the cord blood or by blood gases within 1 hour of birth
Two of the following signs or symptoms to diagnose moderate or severe HIE needed to be present.
- lethargy
- stupor
- coma
- abnormal tone or posture
- abnormal reflexes (absent of decreased responses) which include sucking, grasping, Moro, gagging, and stretching
- low heart rate
- abnormal pupils
- apnea (spontaneous cessation of breathing)
- seizures, clinical evidence of, or severely abnormal amplitude findings on an EEG
Why Hypothermia?
The beneficial effects of mild hypothermia include reducing cell death, decreasing loss of cellular energy, reducing oxygen need and consumption, reducing release of inflammatory substances such as nitric oxide, glutamate, free radicals, harmful neurotransmitters, and stopping the genes that cause neuron death. One concern about hypothermia is that those infants with severe HIE may survive, but at what cost to the parents and society, both psychologically and financially? In infants with an extremely poor prognosis, hypothermia may delay end-of-life decision making.
Method of Inducing Hypothermia
Before transport to a Level 3 NICU, remote centers can use other modalities to induce hypothermia. Gel or ice packs can be placed around the head of the baby or cooling fans can be used to provide cool air circulation around the baby. The core temperature should be continuously monitored and action taken if the temperature gets too low. Rectal temperatures, not axillary temperatures should be used to monitor core body temperature.
At referral centers with a Level 3 NICU, Brain hypothermia can be accomplished with head or total body temperature reduction. Moderate hypothermia is defined as reducing the core body temperature to 33-35 degrees C as measured by a temperature probe in the rectum or esophagus for 72 hours and then slowly rewarming by 0.2 to 0.5 C per hour. Currently, there are two systems, one for selective head cooling and one is a whole-body cooling system. A cooling blanket can be used that contains cooling liquid that circulates and returns for re-cooling depending on the desired rate and magnitude of cooling desired. The second method is a cooling cap that goes on the baby's head and is maintained at the desired temperature.