Birth Asphyxia caused by a reduction in the supply of blood or oxygen to a baby's brain during birth is a major cause of death and brain damage. It occurs in approximately 1 per 1000 births and causing around 20% of all cases of cerebral palsy.
Jacobs S, Hunt R, Tarnow-Mordi W, Inder T, Davis P., in 2007 found that brain hypothermia, induced by cooling a baby to around 33 degrees C for 3 days after birth has recently proven to be the only medical intervention which reduces brain damage and improves an infant's chance of normal survival after birth asphyxia.
TTM for neonatal encephalopathy has been proven to improve outcomes for newborn infants affected by perinatal hypoxia-ischemia, hypoxic-ischemic encephalopathy or birth asphyxia. Whole-body or selective head cooling to 33°-34° C (91°-93° F), begun within 6 hours of birth and continued for 72 hours, significantly reduces mortality and reduces cerebral palsy and neurological deficits in survivors.8,9,11
The optimal duration of brain cooling in the human newborn has not been established.
In selective head cooling, a cap (Cool Cap) with channels for circulating cold water is placed over the infant's head, and a pumping device facilitates continuous circulation of cold water. Nasopharyngeal or rectal temperature is then maintained at 34°-35°C for 72 hours.3,9
In whole-body hypothermia, the infant is placed on a commercially available cooling blanket, through which circulating cold water flows, so that the desired level of hypothermia is reached quickly and maintained for 72 hours. Rewarming is a critical period and in clinical trials, rewarming should be carried out gradually over 6-8 hours.3,9
A major contributor to global child mortality and morbidity is neonatal encephalopathy after perinatal hypoxic-ischemic insult. Brain injury in term infants as a result of hypoxic-ischemic insult is a complex process evolving over hours to days. This time frame provides a unique window of opportunity for neuroprotective treatment interventions. Advances in neuroimaging, brain monitoring techniques, and tissue biomarkers have improved the ability to diagnose, monitor, and care for newborn infants with neonatal encephalopathy. This helps to predict their outcome.6,7,9
Challenges remain in early identification of infants at risk for neonatal encephalopathy, determination of timing, and extent of hypoxic-ischemic brain injury, as well as optimal management and treatment duration. TTM is the most promising neuroprotective intervention to date for infants with moderate to severe neonatal encephalopathy after perinatal asphyxia and has currently been incorporated in many neonatal intensive care units in developed countries.3,8,9,11
Presently, only 1 in 6 babies with encephalopathy benefit from TTM. Many infants still develop significant adverse outcomes. In order to enhance the outcome, specific diagnostic predictors are needed to identify patients likely to benefit from hypothermia treatment. Studies are being done to determine the efficacy of combined therapeutic strategies with hypothermia therapy to achieve maximal neuroprotective effect.
Uncertainties exist regarding mild to moderate hypothermia as a safe and effective neuroprotective intervention for newborns who have sustained a perinatal hypoxic-ischemic insult resulting in encephalopathy. Completion of ongoing trials, worldwide and long-term follow-up of survivors is vital to evaluate whether widespread implementation should be initiated or if this action is premature.