Sarah Carlyle, a critical care nurse at Rogue Valley Medical Center, displays the heat transfer pads that are used to induce hypothermia in cardiac patients. Cooling unconscious heart-attack victims helps more of them recover without brain damage. (Mail Tribune / Jim Craven)"Chill out" has a whole new meaning for the cardiac care team at Rogue Valley Medical Center.
Doctors and nurses have been lowering some heart-attack patients' body temperature to give them a better chance to avoid brain damage that can occur in connection with cardiac arrest. Patients are rapidly cooled to 91.4 degrees Fahrenheit, maintained at that temperature for 24 hours, then gradually rewarmed to the normal temperature of 98.6.
The technique known as "induced hypothermia" is a relatively new treatment, said Dr. Ken Lightheart, RVMC's chief of cardiovascular medicine, "but within the last year it's become the standard of care in large teaching hospitals."
The treatment is designed for patients who have had a heart attack outside a hospital and gone unconscious — those most likely to suffer brain damage if they recover at all.
"If somebody's down five minutes without good CPR, their survival incidence is pretty low," said Todd Kotler, a cardiologist who has used hypothermia to treat cardiac patients.
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The science for explaining why chilling the body reduces brain damage isn't completely clear, Kotler said, but reducing body temperature slows the brain's metabolic rate and its demand for oxygen.
"The chilled brain isn't struggling as hard to function," he said. Chilling also reduces the brain damage associated with "refusion" (the return of blood to the brain).
Patients at RVMC are cooled by a device called Arctic Sun, manufactured by Medivance, a Colorado-based company. Pads filled with cold water are wrapped around the patient's trunk and thighs. The water absorbs body heat and removes it. Sensors in the Arctic Sun monitor the patient's temperature and adjust the water temperature to maintain the patient's body temperature at 7.5 degrees below normal.
Cooling patients any more would cause more stress on people who are already quite ill, Kotler said.
Patients feel nothing because they're unconscious, said Jo Jacovone, a critical care nurse who helped bring the equipment to RVMC. They're given drugs to prevent involuntary shivering.
Two nurses oversee a patient during the treatment: one monitors the equipment; the other, the patient.
"It's very intense nursing," Jacovone said.
Lightheart said the equipment also can be used to treat other conditions that require cooling the patient, such as high fevers or traumatic brain injuries.
He said studies of hypothermia's efficacy convinced RVMC staff they wanted to bring it to Southern Oregon. In one European study involving 275 patients, 55 percent of the induced hypothermia group had a favorable neurologic outcome six months after their heart attack, compared to only 39 percent of those who were not chilled.
Six months after their heart attacks, 41 percent of the hypothermic subjects in the study had died; but 55 percent of those who were not chilled were dead.
"The studies are limited in size," Kotler said, "but the results are very encouraging."
"This treatment isn't necessarily going to cure the patient," Lightheart said, "but it's going to make their chances (of recovery) higher."
Reach reporter Bill Kettler at 776-4492 or e-mail:bkettler@mailtribune.com
