By crushing and shaving the sharp edges off tiny ice crystals, scientists in Chicago have created a slurry that can be pumped into veins, arteries and the lungs. The life-saving, Slurpee-like slurry rapidly cools the body from the inside out, giving doctors more time to treat patients while staving off harmful complications, saving lives.
"What you end up with is not what you'd get from the local 7-11," said Ken Kasza of the Argonne National Laboratory in Illinois. "With a Slurpee you get the liquid but not the ice. In our slurry you get the liquid and the ice."
Protective cooling, as rapidly cooling the body to prevent inflammation, acidosis and other problems is called, has been around unintentionally for thousands of years. It explains why, when a person falls into a frozen lake or river and doesn't breathe for as long as 90 minutes, they can be successfully revived with little or no brain damage.
For decades scientists have artificially induced localized and universal hypothermia using cooling blankets, cold, liquid saline solutions and packed ice chunks, in surgical patients to protect them.
These techniques are effective, but slow. Speed is critical for protective cooling. Pumping iced saline directly into veins, arteries and lungs lets doctor cool organs much more quickly than cooling externally, increasing survival rates and the time doctors have to treat a patient. During a surgery, that could mean having more than two hours to operate on a patient, instead of the 30 minutes currently available for some procedures.
"The fact that we have high ice loading means that we can absorb many times more heat than with cold saline," said Kasza. "That means that the amount of coolant needed to reduce body temperature is reduced dramatically."
Kasza's Argonne colleague, Yue Wu (Ryan), ran initial tests of the ice, compared with cold saline during an angioplasty, and found the slurry is about five times more effective at cooling the body.
In large animals, the scientists were able to at least triple the window of time to treat a heart attack, from 10 to 15 minutes for a heart attack, up to 30 and 45 minutes. The scientists think they could extend that time even longer; they discontinued the experiments early to ensure that all animal survived. The scientists are currently seeking FDA approval to test the ice slurry on humans.
The Argonne National Laboratory and University of Chicago scientists created their life-saving slurry by first freezing large chunks of saline solution into a clear, solid mass. Then they mechanically ground up the ice using a special, propriety method that turns the sharp, crystalline ice into round, smooth balls.
The tiny, icy spheres, small enough to fit through a 1-mm-wide catheter, can then move around one another and not become stuck, like what can happen in a 7-11 Slurpee, allowing for a quick brain freeze. The table-top-sized machine can produce about three to four liters of ice slurry at a time, more than enough to treat a patient.
Chilling down the brain and spinal cord is just one area doctors hope to use the slush. Organ transplantation, laproscopic kidney surgery and heart attacks are all areas where the life-saving saline slurry could be used, say the doctors.
Once the ice slurry melts the saline is absorbed into the body harmlessly. If it is injected into the lungs, most of the saline is sucked back out, while the remaining solution is then absorbed into the body.
This is all good news, says James Black, a surgeon at the Johns Hopkins University who was not involved in the research.
"If the research shows that it the body cools faster, that's a great advantage," said Black.
Ultimately the Argonne and University of Chicago scientists want to use the icy slurry outside the hospital, by equipping ambulances and paramedics with bottles of ice slurry to treat patients. It's an idea that Black is hesitant about. Without general anesthesia, protective cooling could actually worsen acidosis, he said, which is one of the conditions protective cooling is supposed to help.
Without anesthesia, as the body cools it shivers to generate heat. Shivering uses a lot of energy, and the products, including lactic acid, acidifies the body, creating another set of problems doctors must deal with. Administering anesthetic is necessary during protective cooling to ensure that the body doesn't shiver.
The doctors are also experimenting with mixing synthetic blood substitutes and micro injections of oxygen into the slurry, which would also help patients by providing oxygen and nutrients to the body during a traumatic event, potentially staving off acidosis, among other problems. This would be particularly useful during heart attacks outside a hospital, where as few as five percent of patients survive.
The Chicago team hopes to begin FDA trials of the basic ice slurry within the year. They are also speaking with an unmentioned biomedical company to market the slurry producing process. If everything goes well, their life-saving slush could be cooling patients in a few years.
"We want to be able to get this stuff into the small capillaries deep in the body, heart and brain, to protect cells from dying from a lack of oxygen," said Kasza.
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