Cooling patients who have suffered cardiac arrest can lessen damage to the brain; now researchers are looking for other ways to use induced hypothermia.
The last Dr. Peter Franklin remembers, he was lying on a table in the cardiac catheterization lab in a Miami hospital when his chest started to hurt.
Then he died. The medical team raced to restart Franklin’s heart, then placed a stent in a blocked artery to allow blood to again flow freely. His doctors also worked to save his brain, using a technique that’s as old as ancient Greece — hypothermia.
With recent studies lending scientific credibility to the practice, doctors now know that lowering a patient’s body temperature — using methods including cooling blankets or an infusion of cold fluid — can improve brain recovery in patients who are comatose after cardiac arrest. The goal is to decrease the dangerous flood of inflammation, toxic enzymes, and free radicals that occurs when oxygen returns to the brain after the heart resumes beating after arrest, said Dr. Benjamin Scirica, an assistant professor of medicine at Harvard Medical School and Brigham and Women’s Hospital.
It’s believed that the idea of cooling patients began with Hippocrates, who advocated that wounded soldiers be covered with snow or ice. In the 1890s, William Osler, one of the founders of Johns Hopkins Hospital and considered the father of modern medicine, placed typhoid fever patients in cold baths. By the 1950s, efforts shifted to using hypothermia in the operating room during cardiac surgery. But there were drawbacks. At that time, the theory was that cooling worked by decreasing the brain’s use of oxygen and slowing metabolism. Thus, patients were cooled to body temperatures as low as 85 degrees, and kept that way for days. The complications were significant — irregular heart rhythms, infection, bleeding. Excitement over cooling diminished.
Then in the 1980s, at the lab of the late Dr. Peter Safar at the University of Pittsburgh, researchers experimented with milder hypothermia, and found that their animal subjects had improved recovery after cardiac arrest. But widespread interest wasn’t rekindled until 2002, when a pair of studies was published in the New England Journal of Medicine. Two teams of researchers, one in Australia and the other in Europe, studied the effects of cooling patients who had survived a cardiac arrest but showed no meaningful brain function. The methods were simple — ice packs in one study, a machine that generated cold air in another. But the results were striking: Both groups of researchers found that lowering the body temperature to around 91 degrees Fahrenheit for 12 to 24 hours significantly improved brain function. In one study, more than half the cooled patients had a good neurologic outcome, compared with just over a third of patients who were not cooled. The patients who were cooled were also less likely to die.
Shortly after the articles were published, a young hockey player was brought to Boston Medical Center in a coma after a blow to his chest caused a disruption to his heart rhythm, leading to cardiac arrest. A doctor promptly asked the nursing staff to cover the young man with ice. The request sounded “nuts,” said Dr. George Philippides, then the director of the BMC Coronary Care Unit and currently the associate chief of cardiovascular medicine. The hockey player was cooled and ultimately walked out of the hospital. A team at BMC formalized a protocol for cooling patients who are in a coma following cardiac arrest as soon as they arrive at emergency room doors. That protocol is now routinely being used at other Boston-area hospitals for cardiac arrest patients who do not wake up after being resuscitated.
With small studies suggesting that earlier cooling might be better, Boston EMS has developed a method to lower patients’ body temperature with chilled saline kept stocked on all advanced life support ambulances. The question remains open as to whether even earlier cooling, during resuscitation attempts, could yield more benefit. “When is the best time? While they’re on the living room floor, in the ER, in the ICU?” asks Dr. Lori Harrington, the associate medical director of Boston EMS and an assistant professor of emergency medicine at Boston Medical Center. “That’s still not clear.”
With stronger recommendations from the American Heart Association in 2010, 24 hours of hypothermia has become the standard for some patients who don’t wake up after cardiac arrest. No one cooling method has been proven better than any other — although new devices to specifically target the brain rather than the entire body are being developed. While hypothermia is now widely used, questions remain. The 2002 studies looked only at patients with a particular type of cardiac arrest caused by ventricular fibrillation, a quivering of the heart. The jury is still out as to whether patients with other types of arrest will benefit, but doctors have started applying the technology with hopes that it might help.
“We, like most places, tend to cool patients even if they don’t fit the exact group that was studied,” Scirica says, “Because the prognosis is so poor, and cooling is the only treatment we have to offer.” And the applications for therapeutic hypothermia could expand further. Researchers at the University of Miami have published promising data on hypothermia improving outcomes after spinal cord injury. And in Pittsburgh, Dr. Samuel Tisherman, a professor of critical care medicine and surgery, is studying whether extreme hypothermia could play a role in survival after massive hemorrhage. Consider trauma patients whose blood loss is so profound that their hearts stop. Even if the patients’ injuries could technically be repaired, fewer than 10 percent will survive. But what if physicians could freeze time for patients, by quickly bringing their body temperature down to 50 degrees Fahrenheit? “The goal,” Tisherman said, “is preserving brain and other vital organs long enough for surgeons to control the bleeding.” After years of trials in animals, Tisherman and his team are ready to turn to human subjects. With support from the US Food and Drug Administration and the Department of Defense, they are hoping to begin a clinical trial in the coming weeks.
It has been six months since Peter Franklin was hospitalized in Miami. He’s been back to work full time since April and says he suffers “zero deficits.” He remembers nothing of his arrest or subsequent cooling. “For four or five days, we didn’t know yet whether his brain was gone. That was torture,” said his wife, Kathleen Franklin. Fearing the worst, his four children and grandchild traveled to Miami. When Franklin’s breathing tube was removed, the family gathered around his bed, waiting for him to speak. Franklin looked at his wife. He asked her, “How long have I been here?” “About five days,” she told him. He looked around. “Well then,” he said, joking, “where are the cards and flowers?”
SOURCE: Dr. Daniela J. Lamas, The Boston Globe
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