Freeze Your Brain, Save Your Life
Imagine that you have been shot. Nothing vital has been damaged, but a major artery was nicked. Without quick repair, you’ll die of blood loss. You only have 15 minutes, and the drive to the ER is 20. Like 35 percent of all trauma patients, you die from blood loss en route to the hospital. That’s when, as part of an experimental procedure, the medics replace your blood with a cold electrolyte solution. Now surgeons will have an hour to fix the artery, return blood, and revive you.
“It sounds Star Trek-y,” said David King, a surgeon at Massachusetts General Hospital in Boston. His lab did much of the animal work preparing the technique for testing in humans. Now the University of Pittsburgh Medical Center will be the first to test it in humans.
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Blood loss is a pressing concern among trauma surgeons, King said. Many patients who die have fixable wounds—their deaths are from hemorrhage. Death from blood loss accounts for 40 percent of deaths within 24 hours of a traumatic injury, according to the National Trauma Institute, an advocacy group.
The cooling technique is one of several approaches funded by the Department of Defense in early-stage work. Arsenal Medical Inc., based in Watertown, Massachusetts, is also testing another science-fiction-esque treatment, using foam to prevent patients with abdominal wounds from bleeding to death.
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In war, methods to prevent deaths from blood loss are crucial, since about 85 percent of deaths on the battlefield are from bleeds medics can’t compress, according to articles in the Annals of Surgery and Journal of Trauma. Many soldiers die from blood loss before they can get to a hospital, which are an average of an hour away.
“It’s frustrating to know that patients could be saved if only they hadn’t bled to death,” said Sam Tischerman, who’s leading the UPMC cooling study. Right now, if patients have lost about half their blood, they almost never survive, he said. His study has military funding as well from the U.S. Army, though it’s a long way from battlefield use, Tischerman said.
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The trial in humans will locate patients whose hearts have stopped after a gunshot wound or other injury. If the patients don’t respond to attempts to restart their hearts, the super-cooled saline solution will be pumped throughout the body beginning with the heart and brain, the two most important organs to preserve. The body temperature will drop to about 50 degrees Fahrenheit (10 Celsius), from 98.6 F (37 C). The surgeon then fixes the injury, replaces the blood, and re-starts the heart, according to the trial protocol. The patients will be not quite dead, but not exactly alive, either, exhibiting no brain activity or pulse.
“This is for a patient whose injuries are fixable if you can stop the clock, buy time, and get the person to the surgeon,” Tischerman said. “Our hope is that we can save some people we can’t right now.”
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The idea behind the cooling solution is to drop the body’s temperature rapidly, King said. Doing so slows the cells’ internal machinery, causing them to go into a hibernation-like state. This decreases the need for oxygen and prevents waste from building up from within the cell. The slower metabolism at the cooled state prevents a patient’s body from decaying while the surgeons repair injuries—like your nicked artery, for example. Studies in pigs and dogs have shown that after an hour of cold suspension, 90 percent of the animals can be revived. The pigs showed no signs of cognitive impairments, according to a 2002 study in the journal Surgery.
Numbers likely won’t be so high in humans, King said. The animals’ lives were exquisitely controlled before the experiments, and none of them had any pre-existing conditions, like diabetes or heart disease, that might complicate a potential rescue.
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As with many trauma trials, the patients will be unable to give informed consent, due to their life-threatening wounds. Because their conditions are severe and there is no alternative treatment, informed consent is waived. Instead, the group is informing the community that the trial will happen, so anyone who objects can opt out.
Ten people will be tested this way, and then compared with another 10, who met trial criteria but didn’t undergo the experimental procedure. Then another group of 10 experimental treatments will be observed, followed by controls, until the researchers gather enough data to tell if the treatment is helpful.
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“Suspended animation isn’t quite right, but people really like to think of it that way,” King said.
Arsenal’s foam targets patients earlier—someone who might die from blood loss but isn’t yet dead. These types of patients, who might be saved if their bleeding is stopped, are sometimes difficult to treat because of the site of the wound. Injuries within the chest cavity may not be readily visible to medics, and are difficult to compress, King said.
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“It’s the same category of injury, but earlier in the timeline,” King said. “It’s a slippery slope down.”
The foam, designed to be injected into the navel, is composed of two liquid precursors. The force of the two reacting spreads the foam through the chest cavity, hardening to apply pressure to any bleed sites. Tests in pigs suggest that the foam could buy patients as much as three hours. That’s enough time to get a soldier to a hospital, or a rural civilian to the nearest trauma center.
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Both projects were funded by a Defense Advanced Research Projects Agency, or DARPA. Over the past 25 years, the military has mostly failed to find solutions to blood loss. Previous attempts at preventing death from blood loss by creating blood substitutes have raised safety concerns. These blood substitutes are aimed at getting more oxygen to deprived tissues. In an April 2008 article in the Journal of the American Medical Association, a meta-analysis of 16 blood substitute studies showed that they led to a 30 percent increase in the risk of dying, and almost tripled the odds of heart attacks.
Both the resuscitation trial and the foam are “way, way out there,” King said. “The scientist in me would be very careful promising anything for a salvage therapy for the most desperate of all situations. You can’t expect miracles.”
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