During HIE cooling therapy, the infant is gradually cooled and maintained at approximately 92 degrees for 72 hours, then gradually rewarmed. This must occur in a Level III or Level IV neonatal intensive care unit with the appropriate equipment for active cooling and the ability to closely monitor the baby’s responses to treatment and provide support as needed.
Monitoring and support must include the following:
- Respiratory support – assisted ventilation, frequent saline suction, and oxygen supplementation
- Positioning and skin care – frequent repositioning to prevent bedsores
- Cardiovascular support – heart monitoring and administration of drugs to regulate heartbeat as needed
- Fluid and electrolyte management – monitoring of kidney function, glucose, and electrolytes with replacement as needed
- Restriction of feeding during therapy
- Sedation – as needed to prevent distress during cooling
- Blood coagulation – monitoring and providing plasma supplementation as needed to prevent blood clots
HIE hypothermia therapy is administered through the use of active cooling, but if transport to an appropriately equipped NICU is necessary, passive cooling may be used to ensure the baby’s core temperature is reduced before the window of opportunity passes.
Active Cooling
Active cooling involves using a special blanket through which water circulates to gradually cool the baby. A temperature probe is placed in the baby’s rectum or esophagus. This may be connected to the cooling blanket to facilitate communication between the devices.
Intravenous lines may be placed through the abdomen where the umbilical cord was attached. This allows the NICU to provide fluids, draw blood, and monitor oxygen. An EEG machine will be attached to monitor for seizures.
The baby’s body temperature will slowly be lowered to 33.5 degrees Celsius, or 92.3 degrees Fahrenheit. After 72 hours, the infant is gradually rewarmed through the circulation of warm water through the cooling blanket.
Selective Head Cooling
Therapeutic benefits may be achieved through selective head cooling. According to the Ann & Robert H. Lurie Children’s Hospital of Chicago, an FDA-approved cap known as a Cool-Cap may be fitted to the infant’s head, through which water circulates to gradually cool the head for 72 hours, after which warmer water is circulated through the device to gradually warm the infant.
According to the Canadian Pediatric Society, selective head cooling and full-body cooling yield similar therapeutic benefits and patient outcomes.
Passive Cooling
Passive cooling is implemented when an infant with HIE must be transported to a Level III or Level IV NICU for cooling therapy. Due to the short time window for commencing treatment, passive cooling is often necessary to achieve the target temperature before the latent period ends.
During passive cooling, heat sources are removed, and the infant is kept in as cold an environment as possible leading up to and during transport. The rectal temperature is monitored every 15 minutes.
One of the risks of passive cooling is overcooling because continuous monitoring equipment is unavailable, and it may be difficult to control ambient temperatures. However, according to the Journal of Perinatology, the benefits may outweigh the risks. Passive cooling may be the only way to ensure the reduced temperature is achieved on time to improve the infant’s outcome.
Is There an Alternative to Passive Cooling during Transport?
Servo-controlled active cooling employs gel packs to facilitate cooling during transport, which may be a superior alternative to passive cooling. According to Acta Paediatrica, an international medical journal, infants who received servo-controlled active cooling more reliably arrived at the NICU having achieved the optimal temperature range. However, any cooling was superior to no cooling.
