Why you should care
Because therapeutic hypothermia is a major advance in the science of resuscitation
In February 2015, Don Smith, 25, slipped, fell and struck his head while walking back to his home in McAdoo, Pennsylvania, after a party at the fire hall in the neighboring town of Tresckow. The Penn State psych major spent the next nine hours unconscious in a snow bank on a night when temperatures plunged to minus-4 degrees Fahrenheit. When emergency responders reached Smith the next morning, he was frozen solid, with no heartbeat, pulse or brain activity.
At Lehigh Valley Hospital in nearby Hazelton, an ER team performed CPR on Smith for two hours while slowly warming his body in preparation for an 18-minute medevac flight to the LVH in Allentown. There, doctors used an extracorporeal membrane oxygenation machine to pump warm, highly oxygenated blood through the unconscious man’s system. Within a few hours, Smith’s heart started beating on its own. A few days later, his brain showed normal activity. And a month after that, a neurologist noticed Smith’s eyes tracking him during an examination. Although Smith lost his toes and both pinkies to gangrene, he otherwise made a complete recovery.
Tisherman’s team lowers body temperature to 50 degrees Fahrenheit by replacing all of the body’s blood with a cold saline solution.
Case histories like this have long tantalized researchers: What are the outer limits of survival? Can humans be placed in suspended animation and successfully revived? Or, more pragmatically, is it possible to rapidly cool trauma patients to well below normal body temperatures, thereby enabling their brains to survive without blood flow while surgeons treat life-threatening injuries? Ten or 20 years ago, this procedure was being tested in labs, and now it’s being used in clinical studies on humans in the U.S., as well as in Germany and other European countries. In China, doctors plan to use the technique to prevent neurological damage during the first human head transplant.
Known as therapeutic or induced hypothermia, this technique is now of particular interest to the military, given that soldiers and marines who might otherwise survive wounds in remote locations often die before reaching field hospitals. If these studies show positive results, then induced hypothermia or similar treatments may be deployed in combat settings, perhaps in forward surgical units and teams or even in helicopters used to evacuate the wounded. The benefits could extend well beyond the military to civilian life. According to a recent report from the National Academies of Sciences, Engineering and Medicine, trauma is the leading cause of death for Americans under the age of 46. The report estimates that optimal care could have prevented up to 20 percent of the 147,790 U.S. deaths from trauma in 2014 — nearly 30,000 lives saved. “There have been pretty remarkable anecdotes and isolated cases of someone being resuscitated, or ‘brought back,’ after injury in a situation where they had been cooled,” says Col. Todd E. Rasmussen, director of the Department of Defense Combat Casualty Care Research Program, based in Fort Detrick, Maryland. “I think all of that has culminated in an interest now in trauma and injury.”
So much so that the Department of Defense is funding the Emergency Preservation and Resuscitation for Cardiac Arrest from Trauma (EPR-CAT) Study, which is led by Dr. Samuel A. Tisherman at UPMC Presbyterian in Pittsburgh. Tisherman is the director of the Center for Critical Care and Trauma Education and the director of the Surgical ICU at the University of Maryland Medical Center. Starting in early 2016, he and his team began screening the ER’s incoming patients, looking for a certain kind of trauma victim who arrived while the trained staff was on site — one with gunshot or knife wounds and bleeding to the point of cardiac arrest. Although the penetrative wounds of such trauma victims usually are reparable, these patients have about a 10 percent chance of survival. Tisherman and his team will treat 10 patients with their extreme cold cure, review their data and procedures, and then enroll an additional 10 subjects. A control patient is enrolled for each patient undergoing the hypothermia treatment.
The EPR-CAT is a continuation of work Tisherman began 20 years ago, when he participated in preclinical studies at the University of Pittsburgh’s Safar Center for Resuscitation Research, which demonstrated the feasibility of induced hypothermia. His current study is the first time the treatment is being used on trauma patients. Tisherman’s team lowers body temperature to 50 degrees Fahrenheit by replacing all of the body’s blood with a cold saline solution that is administered via a tube called a cannula inserted into the aorta, which is the body’s largest artery. “Cooling decreases the body’s need for oxygen and blood flow,” Tisherman says. “CPR isn’t going to work on a trauma patient who has bled to the point of cardiac arrest, because there’s not enough blood to circulate.”
The induced hypothermia is designed to give doctors about an hour to stop the bleeding and operate without worrying about brain damage from lack of blood flow. (At normal body temperatures, that window usually is less than five minutes.) Once the patient is stabilized, the team uses a heart-lung bypass machine with a heat exchanger to gradually restore blood circulation, oxygenation and body temperature as part of the resuscitation process.
Tisherman’s work on the EPR-CAT is part of an international effort to improve the survival rates of patients in shock. According to Rasmussen, the reasons the U.S. is supporting the study include the maturity of science, the success of previous lab trials and the need for medical advances given the number of casualties in the country’s decade-long conflicts. “Part of what’s pushed this over the threshold to say ‘Now is the time to study it’ is the burden of injuries from the wars in Afghanistan and Iraq,” Rasmussen says. “I would say that’s been a big impetus.”
In the EPR-CAT study, it is expected that patients will take anywhere from several hours to several days to regain consciousness once the cold saline solution is flushed from their veins and replaced with blood and their core temperatures are elevated. Since patients selected for the study are unable to give informed consent due to their traumatic wounds, the work is being conducted under the FDA’s exception from informed consent rules, which include community consultation and public notification.
Some medical ethicists ask what happens if a test subject remains in a vegetative state? Given the lousy odds of survival for the trauma victims enrolled in the EPR-CAT study, it would seem logical to assume that most patients would gladly roll the dice and go with the ice. And yet a 2006 study in the Journal of Medical Ethics found that up to 70 percent of patients surveyed were not willing to participate in resuscitation studies that relied on exception from informed consent. The study noted that it is “difficult to know whether that right to conduct scientific research can ever override the principle of patient autonomy.”
A soldier or marine bleeding out far from base may be less concerned about patient autonomy. “We’ve seen [battlefield deployment] with other advances such as blood and blood products, which used to just be in hospitals but now we use in pre-hospital settings and on helicopters,” Rasmussen says. “EPR-CAT has that sort of capability.”