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DENVER – While resuscitation guidelines previously called for up to three successive or “stacked” shocks with minimal time delays between defibrillation attempts for cardiac arrest patients, resuscitation guidelines were revised in 2005 to support single shock protocols with two minutes of chest compressions between defibrillation attempts to minimize interruptions in compressions.
A new study published in The BMJ Today raises questions about the delay in giving the second shock, suggesting it is not associated with improved survival.
Veterans’ Affairs Colorado Health Care System-led researchers said they conducted the study because of the lack of data on how those changes affect survival for patients with cardiac arrest in hospitals.
For the retrospective cohort study looking at 172 hospitals in the United States participating in the Get With The Guidelines-Resuscitation registry from 2004-12, the researchers examined trends in the time interval between first and second defibrillation attempts among 2,733 patients suffering cardiac arrest.
Among 2,733 patients with persistent ventricular tachycardia or ventricular fibrillation (VT/VF) after the first defibrillation attempt, 1,121 (41%) received a deferred, defined as more than one minute, second attempt.
In line with the guidelines, results indicate that the proportion of patients with a deferred second defibrillation attempt doubled from 26% in 2004 to 57% in 2012.
Compared with early second defibrillation, defined as less than a minute, unadjusted patient outcomes were significantly worse with deferred second defibrillation: 57.4% vs. 62.5% for return of spontaneous circulation, 38.4% vs. 43.6% for survival to 24 hours, and 24.7% vs. 30.8% for survival to hospital discharge.
After risk adjustment, study authors determined that deferred second defibrillation was not associated with survival to hospital discharge, with an adjusted risk ratio of 0.89.
A second study, led by researchers from Beth Israel Deaconess Medical Center in Boston, suggests that early administration of epinephrine in hospital is associated with poorer outcomes in patients with cardiac arrest and a shockable rhythm.
The international study team sought to reconcile different guidelines for use of epinephrine, employing the Get With The Guidelines data for nearly 3,000 patients with cardiac arrest at more than 300 U.S. hospitals. More than half, 51%, of patients received epinephrine within two minutes after the first defibrillation, contrary to current guidelines.
Results indicate that receiving epinephrine at that point was associated with a decreased chance of a good outcome, including survival to hospital discharge, compared with patients who were not given epinephrine within this time period.
Authors of both studies point out that their research was observational, so no firm conclusions can be drawn about cause and effect.