Better survival and neurological outcomes in cardiac arrest

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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 “non-shockable” 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 non-shockable 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.”

Perman, a clinical expert in cardiac arrest and post-arrest care, and her colleagues looked at data from 519 patients who had non-shockable 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 37º C to 33º C (91.4º 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% of those who received therapeutic hypothermia had good neurological outcomes as opposed to 26% who did not receive the treatment. Another trial showed 55% of patients with good neurological outcome against 39% 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 neuro-protection, 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.”

Background—Therapeutic hypothermia (TH) attenuates reperfusion injury in comatose survivors of cardiac arrest. The utility of TH in patients with non-shockable initial rhythms has not been widely accepted. We sought to determine whether TH improved neurologic outcome and survival in post-arrest patients with non-shockable rhythms.
Methods and Results—We identified 519 patients after in- and out-of-hospital cardiac arrest with non-shockable initial rhythms from the Penn Alliance for Therapeutic Hypothermia (PATH) registry between 2000-2013. Propensity score matching was used. Patient and arrest characteristics used to estimate the propensity to receive TH were age, sex, location of arrest, witnessed arrest, and duration of arrest. To determine the association between TH and outcomes, we created two multivariable logistic models controlling for confounders. Of 201 propensity score matched pairs, mean age was 63±17 years; 51% were male; and 60% had an initial rhythm of pulseless electrical activity. Survival to hospital discharge was greater in patients who received TH (17.6% vs. 28.9%; p<0.01), as was discharge CPC of 1-2 (13.7% vs 21.4%; p= 0.04). In adjusted analyses, patients who received TH were more likely to survive (OR 2.8, 95% CI: 1.6-4.7) and have better neurologic outcome (OR 3.5, 95% CI: 1.8-6.6) than those that did not receive TH.
Conclusions—Using propensity score matching, we found patients with non-shockable initial rhythms treated with TH had better survival and neurologic outcome at hospital discharge than those who did not receive TH. Our findings further support the use of TH in patients with initial non-shockable arrest rhythms.

University of Colorado Anschutz Medical Campus material
Circulation abstract

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