Switch to cooling blanket spurs new infant brain research
By Carole Bartoo
February 23, 2012
Use of a "cooling cap" within six hours is now the standard of care when an otherwise healthy, full-term infant experiences a serious lack of oxygen, called anoxic brain injury. The therapy uses cool water to bring the temperature of the brain down about five degrees. Vanderbilt took part in the initial studies of the cooling cap, which was found to reduce serious long-term brain damage and death by about one-third.
Now a switch has been made to a cooling blanket instead of a cap. The blanket is as effective in its brain-protecting capacity, but it offers researchers an opportunity to better assess what is happening in the brain as it is cooled.
Pediatric Neurology chief resident, Siddharth Jain, M.D., said by using a cooling blanket, the scalp is free for him to apply a full, nine-lead electro encephalogram (EEG) monitor along with a newer device called a near-infrared spectroscopy (NIRS) monitor to find out what is going on beneath a baby's scalp.
The EEG can detect seizures, while NIRS measures how the brain uses oxygen. The information collected so far has been surprising.
"We already know the EEG detects seizures that cannot be seen in these babies. Up to 80 percent of seizures in babies with anoxic brain injury have no overt clinical signs. Other studies have shown that these babies can have between 100 and 120 seizures during the first 72 hours of life," Jain said.
"These seizures are different than those in epilepsy. They are very aggressive in the first 48 hours and difficult to control. We don't know for sure, but the consensus is the seizures themselves cause further damage."
Jain is working with Barbara Engelhardt, M.D., associate professor of Neonatology, to closely examine what is happening in the first 72 hours after an anoxic injury - the critical window of opportunity in which the cooling seems to have its maximum brain-preserving effect.
For this observational study, William Walsh, M.D., neonatologist and director of Nurseries, switched the NICU to the cooling blanket to allow the researchers to enroll the one or two babies brought to Vanderbilt every month with anoxic brain injury.
The first goal is to use EEG and NIRS to more quickly and accurately predict the severity of the anoxic injury. Currently, an MRI is used to give doctors a peek at structural damage in the brain, once the initial injury has stabilized, to assess long-term changes. But the predictive value of long term damage is not very great.
Engelhardt says EEG and NIRS provide information from day one about seizure activity as well how the brain is using oxygen.
These two pieces of information can describe changes after the initial injury, and may help provide a better measure of the effects on long-term outcomes.
A second goal is to use the monitors to test new therapies. The hope is the monitors could more quickly assess the effectiveness of therapies is controlling seizures, or better balancing nutrient consumption after injury in the hope of further reducing the risk of permanent brain damage.
"When a brain cell is injured, it can go one of two ways: it can die or recover," Walsh said. "The goal is to limit damage to as small an area as possible.
"The cooling cap was a general way to slow down the potential for further damage, but in the 15 years we have been using it, we have learned a lot about what is happening biochemically in anoxic injury and how we can further impact that damage.