AURORA, Colo. (Nov. 24, 2015) - Survivors of cardiac arrest who remain in comas have better survival and neurological outcomes when their body temperatures are lowered, according to new research by Dr. Sarah Perman at the University of Colorado Anschutz Medical Campus.
Therapeutic hypothermia involves decreasing the body temperature to protect the brain when blood flow is reduced from a cardiac arrest, when the heart stops pumping and the patient has no pulse.
Previous studies have shown the therapy effective on patients with so-called `shockable' heart rhythms like ventricular fibrillation. But Perman's research demonstrates that it's also effective on patients with `nonshockable' rhythms when there is no pulse and the patient is in a coma.
"Prior to our study, there was minimal data to support the use of this treatment on patients with nonshockable rhythms," said Perman, an assistant professor of emergency medicine at the University of Colorado School of Medicine. "As a result, the therapy was not widely used with these patients."
Every year, 530,000 Americans suffer cardiac arrest and 300,000 of them happen outside of a hospital.
Perman, a clinical expert in cardiac arrest and post-arrest care, and her colleagues looked at data from 519 patients who had nonshockable heart rhythms between 2000 and 2013.
They found those who received therapeutic hypothermia were 2.8 times as likely to survive to be discharged from the hospital and 3.5 times more likely to have better neurological outcomes - returning to their baseline mental state - than those who did not have the treatment.
Physicians who use the technique employ cooling wraps to drop the patients' temperature from approximately 37 degrees Celsius to 33 degrees Celsius (91.4 degrees F). The therapy has shown to reduce damage to the brain following a cardiac arrest, though scientists continue to investigate why this occurs.
Landmark trials in 2002 studying shockable patients found 49 percent of those who received therapeutic hypothermia had good neurological outcomes as opposed to 26 percent who did not receive the treatment. Another trial showed 55 percent of patients with good neurological outcome against 39 percent who didn't have the therapy.
"Neurologic injury after cardiac arrest is devastating," said Perman, who like most physicians at CU Anschutz is both an active researcher and practicing clinician. "We have one chance to give some form of neuroprotection, and that's immediately after the arrest."
She said therapeutic hypothermia should be more widely used in comatose patients to protect neurological function.
"We know that patients benefit from this therapy," said Perman, noting the importance of delivering meaningful research from the laboratory directly to the patient. "Therefore, one of our next challenges is to tailor the hypothermia treatment to the patient's specific injury in order to improve outcomes further."
The study was published in the latest edition of the journal Circulation. It was funded by the National Institutes of Health.