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30-04-2012 | Cardiology | Article

Current strategies fail converted-shockable cardiac arrest patients


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MedWire News: Immediate defibrillation may not help cardiac arrest patients who convert from a nonshockable to a shockable rhythm during resuscitation attempts, research suggests.

The chances of patients with initial nonshockable rhythms surviving is much lower than for those with initial shockable rhythms, regardless of whether they convert to a shockable rhythm during resuscitation, report Timothy Mader (Baystate Medical Center, Springfield, Massachusetts, USA) and colleagues.

The 30,939 patients in the study were identified in the Cardiac Arrest Registry to Enhance Survival and most (65.7%) had a never-shockable rhythm. The survival rate at hospital discharge in this group was just 4.1%.

A further 10.4% of patients had an initial nonshockable rhythm, but converted to a shockable rhythm during resuscitation. Current guidelines recommend immediate defibrillation if a patient converts to a shockable rhythm.

"Controversy exists regarding the appropriateness of this approach because alternatives have never been studied," say Mader et al. Their findings suggest that the approach may not be appropriate, because the survival rate among patients in this study was just 4.7%.

By contrast, 26.9% of patients with an initial shockable rhythm survived to discharge.

The pattern persisted on multivariate analysis, with converted-shockable and never-shockable rhythms reducing patients' survival chances by more than 70%, relative to a shockable rhythm.

However, size of the negative impact of a converted- or never-shockable rhythm appeared to vary according to the initial rhythm. Patients with initial pulseless electrical activity who converted to a shockable rhythm had a significantly poorer chance for survival than those who had pulseless electrical activity throughout resuscitation attempts, with their survival odds reduced 87% and 75%, respectively, relative to patients with an initial shockable rhythm.

But the reverse was true for patients with initial asystole rhythm. Their survival chances relative to patients with an initial shockable rhythm were reduced by 85% if they converted to a shockable rhythm and 90% if they did not.

"These findings support the contention that converted shockable and initial shockable rhythms may not be the same," Mader and team write in Resuscitation.

"The major implication of this finding is that alternatives to the existing resuscitation algorithm, which are tailored to patients with converted shockable rhythms, should be investigated."

By Eleanor McDermid

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