Cooling Cardiac Arrest Patients Ups Survival

Heart attack patients improve with cooling

(RxWiki News) A system of cooling then gradually re-warming cardiac arrest patients following resuscitation increases the outcomes. Yet the treatment remains underused.

Lowering the temperatures of patients at a centrally-located hospital increases the chance of good brain function. That was the case even when patients were transferred to the central hospital for care. The American Heart Association recommends this protocol, but U.S. cardiologists have been slow to use it.

"Ask your cardiologist about therapeutic hypothermia."

The cooling treatment, called therapeutic hypothermia, was implemented by a network of first responders, emergency room departments and more than 30 independent hospitals within 200 miles of Minneapolis.

Dr. Michael Mooney, the study’s lead author and director of the therapeutic hypothermia program at Minneapolis Heart Institute, where the protocol was developed, said the system of care provides essential therapy to victims of out-of-hospital cardiac arrest.

Investigators followed 140 patients who suffered out-of-hospital cardiac arrest between February 2006 and August 2009. In each case their heartbeat and circulation were restored within an hour of collapse, but they remained unresponsive. About half of all patients who received the treatment were being treated for a severe form of heart attack called ST-elevation myocardial infarction.

Ice packs were used to begin the cooling process, which started during transport to the hospital and in the emergency department. All of the patients were admitted to Abbott Northwestern Hospitals for therapeutic hypothermia and re-warming. Of those, 107 were transferred from other hospitals.

Over a period of up to four hours, patients’ core body temperature was lowered to 92 degrees and maintained at that level for about 24 hours. Over the following eight hours, doctors gradually re-warmed them to a normal temperature.

They discovered that among the 56 percent of patients who survived to hospital discharge, 92 percent had positive neurological scores, which indicates there was no severe injury. Prior to the program, 77 percent had positive neurological scores. Older patients fared slightly worse from a neurological perspective. Additionally, they found that the death risk rose by 20 percent for each hour of delay between the return of spontaneous circulation and cooling.

If a cardiac arrest patient survives the initial oxygen loss, they often struggle when blood flow is rapidly restored, which is often fatal. Therapeutic hypothermia reduces the damage that can occur in the 16-hour window after blood flow is restored.

The Minneapolis Heart Institute Foundation funded the study.

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Review Date: 
July 7, 2011