Justin Salerian knows a thing or two about thermodynamics, lab animals, and the urban legends surrounding icy rivers. That sounds like a random assortment of knowledge, but, as the current Vascular Neurology Fellow at Tulane University, Dr. Salerian – in partnership with Drs. Aimee Aysenne and Robert Schock – is combining all three in a study to see how therapeutic hypothermia can help stroke patients.
In the past, doctors had limited means of intervening in a stroke. “About 20 years ago there was nothing you could do for an occluded blood vessel in the brain. [We could only] give them an aspirin to hope [to] prevent another one from happening,” Salerian says.
In the 1990s, a drug called Tissue Plasminogen Activator (tPA), which functions as a kind of Drain-O for blood clots – breaking up the clot and opening up the vessel – entered the market. It was joined over the last decade by catheter devices that can enter the blood vessel and mechanically remove a clot. Both of those methods were huge advances which together have improved outcomes by 25-40% for big strokes.
But, Salerian asks, what if there were a way we could protect endangered brain tissue that has not yet died? If doctors could slow down the metabolic, inflammatory, and dying processes that occur after brain injury, they could save a lot of brain, particularly if this is done before performing the treatments mentioned above.
Salerian’s suggested method to do this is “literally 2,000 years old”: therapeutic hypothermia. Once the body’s core temperature plummets to about 33 degrees Celsius, the threshold for “mild hypothermia,” the metabolic processes slow enough that the brain tissue dies much slower, making intervention much more viable.
Currently, Salerian and Aysenne are running a study testing a device that has cooled people with heart attacks on average in a mere 27 minutes – five to ten times faster than other previous methods. “Speed matters,” says Salerian. “It’s not just as simple as, ‘Can you get to the temperature or not?’ It’s about how fast you can do it.”
The device is called the Life Recovery System ThermoSuit. The suit lies flat on a hospital bed but then inflates around the patient once he/she is placed on it, creating a reservoir. “Like a sleeping bag, but nice and tight,” Salerian says. He explains that the device is so effective because it simulates an icy river. Rapidly flowing ice-water doesn’t have time to heat up near the body and instead constantly moves over the patient’s skin, removing heat.
The ThermoSuit system also quickly disarms the body’s natural defenses of shivering and vessel constriction by allowing the skin to get cold first – below 10 degrees C in about five minutes, Salerian says. “When the skin hits 10 degrees C, the little muscles that control blood vessel constriction can no longer fire, and they actually (paradoxically) open, allowing blood to rush towards the skin and act like a radiator,” he explains. “So now the skin – which is supposed to be this great organ for thermal regulation, protecting you against getting cold – is now working for us to remove heat with this device.”
In a few studies, when the device was used on select cardiac arrest patients, rates of successful neurological outcomes jumped up to 80-90 percent, as compared to 50 percent with other cooling methods. Salerian and his team think this was because the cooling occurred so much faster. “That’s our belief. Now we have to verify that it can work in a stroke,” he says. If this device performs well in their phase II trial, Salerian and the Tulane team could revolutionize stroke treatment worldwide.
by Ashlyn Stewart