A new study has found that coordinated therapeutic hypothermia (TH) increases the portion of survivors with good brain function by cooling, then gradually rewarming people who had been resuscitated after an out-of-hospital cardiac arrest (OHCA).

Researchers at the Minneapolis Heart Institute Foundation (MN, USA) developed the Cool It protocol, which established TH as the standard of care for OHCA across a regional network of hospitals transferring patients to a central TH-capable hospital. Between February 2006 and August 2009, 140 OHCA patients who remained unresponsive after return of spontaneous circulation were cooled and then rewarmed with the use of an automated, noninvasive cooling device; 75% of them were transferred to the central TH hospital. Positive neurological outcome was defined as Cerebral Performance Category (CPC) of 1 or 2 at discharge.

An analysis of the results showed that overall survival to hospital discharge was 56%, and 92% of survivors were discharged with a positive neurological outcome; survival was similar in transferred and nontransferred patients. Nonventricular fibrillation arrest and presence of cardiogenic shock were associated strongly with mortality, but survivors with these event characteristics had high rates of positive neurological recovery (100% and 89%, respectively). A 20% increase in the risk of death was observed for every hour of delay to initiation of cooling. The study was published in the July 12, 2011, issue of Circulation.

"We've shown that a fully integrated system of care, from EMS through hospital discharge, can provide this essential therapy to victims of out-of-hospital cardiac arrest across a broad geographic region,” said lead author Michael Mooney, MD, director of the TH program at the Minneapolis Heart Institute. “If you have a cardiac arrest 200 miles away or on our doorstep, the quality of the outcomes is identical.”

Therapeutic hypothermia, also known as protective hypothermia, is a medical treatment that lowers a patient's body temperature to help reduce the risk of the ischemic injury to tissue following a period of insufficient blood flow. This may be due to cardiac arrest or the occlusion of an artery by an embolism, as occurs in the case of strokes. TH may be induced by invasive means, in which a catheter is placed in the inferior vena cava via the femoral vein, or by noninvasive means, usually involving ice packs, a chilled water blanket or torso vest, and leg wraps in direct contact with the patient's skin.

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