Body Temperature May Matter After Cardiac Arrest
Research suggests cooling body to 89.6 degrees Fahrenheit might improve survival, protect brain
Wednesday, November 7, 2012
Researchers also found that cooling cardiac arrest patients could result in greater brain function and the ability to perform normal daily tasks, such as bathing and dressing, after recovery.
During cardiac arrest, the heart suddenly stops working. If a person's heartbeat is restored but they are comatose, treatment may include lowering the patients' body temperature in an attempt to decrease the amount of oxygen they need, to prevent brain damage. In conducting the study, the researchers sought to determine the ideal cooling temperature, which would provide the best outcomes for cardiac arrest patients.
"Since extremely low temperatures below [86 degrees Fahrenheit] are associated with complications, it's critical to know the optimal level of cooling," lead researcher Dr. Esteban Lopez-de-Sa, head of the Cardiac Critical Care Unit and Clinical Cardiology at La Paz University Hospital in Madrid, Spain, explained in a news release from the American Heart Association (AHA). "The aim of the study was to provide initial information for future research about whether controlling hypothermia levels can improve outcome."
The study involved 36 people in Madrid who suffered cardiac arrest outside of the hospital between March 2008 and August 2011. On average, the patients were 64 years old, and 89 percent were men. All of the participants were white.
The participants were randomly assigned to receive cooling treatment to either 89.6 degrees or 93.2 degrees Fahrenheit for 24 hours. The patients were cooled internally with cold saline that was administered through an IV. An internal catheter and temperature-management system also was inserted directly into the main vein from the lower body to the heart. This treatment was followed by gradual rewarming for 12 to 24 hours.
The researchers found that 44 percent of those who were cooled to 89.6 degrees Fahrenheit following cardiac arrest survived without severe brain impairment six months later. In contrast, only 11 percent of those whose body temperature was lowered to 93.2 degrees Fahrenheit had the same outcome.
The findings were presented Tuesday at the AHA's annual meeting in Los Angeles, and also published Nov. 6 in the journal Circulation.
Commenting on the research at an AHA press briefing, Dr. Elliot Antman, a professor of medicine at Harvard Medical School and cardiologist at Brigham and Women's Hospital in Boston, said that when he and other experts at the meeting saw the study results, "our faces lit up because there is very little in the way of randomized trials in the field of resuscitation science."
A randomized trial -- one in which patients are randomly assigned to different treatments for comparison -- is considered a reliable scientific method.
"In the 32 years that I've been caring for patients in the coronary care unit," Antman noted, "this is a very challenging set of patients to have to deal with. Those who've had an out-of-hospital cardiac arrest often have these horrible neurologic outcomes, despite successful resuscitation."
The study is "extremely encouraging" and may "help refine this important therapy for our patients who suffer these very serious events," Antman explained. "We know that cooling is cerebrally protective, but in this era where we really want to do the best we can for patients, we are looking for ways to optimize our therapy," he added.
But Lopez-de-Sa and colleagues stressed that larger studies are needed to confirm if cooling is responsible for improved outcomes among the cardiac arrest patients.
"Although the results suggest a better outcome with lower levels of target temperature, they should be interpreted with caution," noted Lopez-de-Sa, because the association does not prove a cause-and-effect relationship. The results "may be due to multiple factors other than the effect of lower target temperature," he said in the AHA news release.
Roughly 383,000 people suffer cardiac arrest outside of a hospital in the United States every year, according to the AHA. The condition is fatal unless cardiopulmonary resuscitation (CPR) and emergency medical care is provided immediately to restore a normal heartbeat.
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