Therapeutic hypothermia may decrease likelihood of survival following in-hospital cardiac arrest

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Providing therapeutic hypothermia to patients who suffer in-hospital cardiac arrest may decrease their chance of survival, according to an observational cohort study.

The researchers found that patients had a lower likelihood of survival to hospital discharge and a lower likelihood of favorable neurological survival if they used therapeutic hypothermia compared with receiving usual care. They said therapeutic hypothermia is also referred to as targeted temperature management.

Lead researcher Paul S. Chan, MD, of Saint Luke’s Mid America Heart Institute in Kansas City, Missouri, and colleagues published their results online in JAMA on Oct. 4.

They noted that therapeutic hypothermia is recommended for comatose survivors of out-of-hospital and in-hospital cardiac arrest, although it has only been shown to improve survival in patients who have an out-of-hospital cardiac arrest.

“These findings do not support current use of therapeutic hypothermia for patients with in-hospital cardiac arrest,” the researchers wrote.

For this analysis, the researchers gathered data on 26,813 patients who were successfully resuscitated after suffering an in-hospital cardiac arrest between March 1, 2002 and Dec. 31, 2014 in 355 U.S. hospitals. They defined cardiac arrest as absence of a palpable central pulse, apnea and unresponsiveness.

The patients enrolled in the Get With the Guidelines-Resuscitation registry, an American Heart Association-sponsored prospective, national, quality improvement registry of in-hospital cardiac arrest. The researchers linked the registry data with Medicare files to find the association between hypothermia treatment and one-year survival.

The 6 percent of patients who were treated with therapeutic hypothermia were younger, less likely to have a cardiac arrest in the intensive care unit and more likely to have an initial cardiac arrest rhythm of ventricular fibrillation, according to the researchers. Patients with therapeutic hypothermia were also more likely to have an MI before their cardiac arrest and less likely to have an acute stroke at the time of their cardiac arrest.

The researchers matched 1,524 patients treated with hypothermia to 3,714 patients who were not treated with hypothermia. The groups were well-balanced in terms of age, sex, race, initial cardiac arrest rhythm, location of arrest and comorbidities. The mean age was 62.2 years old, while 57.5 percent of patients were male and 68.0 percent were white.

Among the propensity score-matched cohort, 27.4 percent of patients treated with therapeutic hypothermia and 29.2 percent of non-hypothermia-treated patients survived to hospital discharge. In addition, 29.1 percent of patients in the hypothermia-treated group and 45.0 percent of patients in the non-hypothermia-treated group died during the first day.

Therapeutic hypothermia was associated with a lower likelihood of in-hospital survival and favorable neurological survival for all rhythms. The researchers found that 17.0 percent of hypothermia-treated patients and 20.5 percent of non-hypothermia-treated patients had favorable neurological survival, which represented a statistically significant difference.

After one year, 14.2 percent and 14.1 percent of patients, respectively, were alive. The one-year survival rates were similar between the groups based on rhythm type, as well.

The researchers cited a few limitations of the study, including that the registry did not collect detailed data on hypothermia protocols and treatments for each patient. The trial might have also included patients who were not comatose following cardiac arrest. In addition, they mentioned that there is variability in assessing neurological status, which could have affected the results for favorable neurological status. Further, the findings might not be generalizable to hospitals that do not participate in the registry.

“These observational findings warrant a randomized clinical trial to assess efficacy of therapeutic hypothermia for in-hospital cardiac arrest,” the researchers wrote.