Out-of-Hospital Cooling for Cardiac Arrest Feasible

July 14, 2011

July 13, 2011 (Minneapolis, Minnesota) — A new protocol to cool out-of-hospital cardiac-arrest (OHCA) patients has been successfully incorporated into an existing regional ST-segment-elevation MI (STEMI) network in Minnesota, with improved outcomes [1].

While therapeutic hypothermia (TH) is recognized as effective in treating cardiac arrest--the AHA has endorsed it--the treatment is underused in the US, say Dr Michael R Mooney (Abbott Northwestern Hospital, Minneapolis, MN) and colleagues in their paper in the July 12, 2011 issue of Circulation. Data on the first 140 patients included in their program, from February 2006 to August 2009, have generated several important findings, they note.

The same number died who died prior to the program, but in those who survived, there was a jump in neurological outcome.

Most important, the cooling appears to improve neural recovery. "The key concern when we started this was whether we were just going to keep people alive who were severely brain damaged. But this has not been borne out," second author Barbara T Unger (Abbott Northwestern Hospital) told heartwire . "The same number died who died prior to the program, but in those who survived, there was a jump in neurological outcome, with 92% of patients having a positive neural recovery compared with 77% before we started the program, which was a profound finding."

In fact, the figures show that TH tends to produce a dichotomy of outcomes--excellent neurological result or death--rather than a continuum of outcomes that include severe and permanent neurological impairment.

TH Applicable to Broad Population, But Appropriateness Criteria Apply

The protocol, dubbed Cool It, incorporates TH as a standard of care into the regional STEMI network of 45 emergency-medical-service units and 33 hospitals within a 210-mile radius of Minnesota. Cooling with ice packs begins in the ambulance or the local hospital, and then the patient is transferred to the central TH-capable hospital, Abbott Northwestern, where the body temperature continues to be lowered for three to four hours, and is maintained at 92ºF (33ºC) for the next 24 hours, using the Arctic Sun device (Medivance, Louisville, CO). Over the following eight hours, physicians gradually rewarm the patients to normal temperature.

As well as the excellent numbers on neural recovery, the data show that survival rates were comparable between patients who were transferred for care (n=107) and those who went straight to Abbott Northwestern. However, each one-hour delay in the initiation of cooling reduced survival by 20%, thereby illustrating the importance of prehospital cooling, say the researchers.

And in patients also requiring emergency STEMI treatment, therapeutic hypothermia and PCI were performed concurrently, without delay to either. This finding is "crucial," say Mooney et al, "given that a significant proportion of OHCA patients who survive to admission will have STEMI requiring timely PCI."

The protocol also included high-risk patients--those with nonventricular-fibrillation arrest, those in cardiogenic shock, the elderly, and those with an extended time between collapse and return of spontaneous circulation (ROSC), who have historically been excluded from clinical trials of therapeutic hypothermia--and showed that outcomes in these patients were better than expected in terms of both overall survival and the quality of neurological outcome.

All of these findings indicate that "consideration should be given to broadening the target population for TH," say Mooney et al.

"We have demonstrated that TH protocols that incorporate simple, noninvasive surface cooling before hospital arrival can provide an effective rescue therapy for OHCA and should readily be adopted within the context of existing STEMI networks."

This is a horrific treatment for family to watch, and if it's absolutely futile, there's no point.

However Unger cautions, "You still need to be appropriate with when you apply this, you still have to have that initial, 'Should we do this?' This is a horrific treatment for family to watch, and if it's absolutely futile, there's no point, so we wouldn't, for example, use it in a terminally ill cancer patient."

And she points out that the numbers in the Cool It program are still small, and for this reason it will be important to combine the findings with those of other centers, a project that is ongoing. Under the umbrella of the International Cardiac Arrest Registry (INCAR), the Minneapolis team will work together with five other US institutions to pool patient data, she notes.

"This is so new that everybody working together is the only way to do this."

An unrestricted grant to support data collection was provided by Medivance. The authors report no conflicts of interest.

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