Heart resuscitation guidelines questioned

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DefibTwo recently published studies have evaluated treatments for patients with cardiac arrest in hospital. The first study suggests that advice to delay giving a second heart shock, known as defibrillation, to patients with cardiac arrest in hospital is not associated with improved survival.

Guidelines previously called for “stacked” shocks with minimal time delay between defibrillation attempts. But in 2005 the guidelines were revised to recommend deferring a second attempt at defibrillation to allow time for chest compressions. However, data on the effect of these changes on survival for patients with cardiac arrest in hospital are lacking.

So a team of US-based researchers used data from a national registry to examine trends in the time interval between first and second defibrillation attempts among 2,733 patients undergoing cardiac arrest in 172 US hospitals. In line with the guidelines, the proportion of patients with a deferred second defibrillation attempt doubled from about 25% in 2004 to slightly more than 50% in 2012. However, deferred second defibrillation was not associated with improved survival.

This is an observational study so no firm conclusions can be drawn about cause and effect, but the authors say the findings raise questions about the specific benefit of deferred second defibrillation attempts for patients in hospital. They suggest that further study is necessary to understand whether current guidelines need reconsideration.

The second study suggests that early administration of epinephrine (adrenaline) in hospital is associated with poorer outcomes in patients with cardiac arrest and a shockable rhythm (these are certain categories of arrest-associated heart rhythms in which the first line therapy is an electrical shock to restore a normal heart rhythm).

Epinephrine has been used in resuscitation after cardiac arrest for decades. But there are currently differing recommendations for treatment. For instance, the American Heart Association (AHA) recommends epinephrine after the second defibrillation, while the European Resuscitation Council recommends it after the third defibrillation.

And clinical practice patterns suggest that epinephrine is used even earlier, such as after the first defibrillation. So, an international team of researchers set out to describe the use of epinephrine during cardiac arrest in hospital and to assess compliance with AHA recommendations. They used data from the same US national registry for almost 3,000 patients with cardiac arrest at more than 300 US hospitals. Over half (51%) of patients received epinephrine within two minutes after the first defibrillation, contrary to current guidelines.

Furthermore, receiving epinephrine at this time point was associated with a decreased chance of a good outcome, including survival to hospital discharge, compared with those who were not given epinephrine within this period. The same research group previously published a study showing a different association of epinephrine in patients with non-shockable categories of rhythms—early epinephrine was associated with improved outcomes in this category of patients.

Again the authors point out that this is an observational study so no firm conclusions can be drawn about cause and effect. But they say these findings “might be relevant to guideline developers, educators, and clinicians involved with the care of such patients.”

In a linked editorial, experts from Warwick Medical School say the results from the two studies should inform medical practice. “The finding of widespread non-adherence with clinical guidelines should prompt those responsible for organising or delivering advanced life support to review their practice and ensure that it is informed by the latest clinical guidelines,” they explain. They add that while “the jury remains out” on the safety or effectiveness of adrenaline in cardiac arrest, “adrenaline should be given in accordance with current guidelines, and it should be deferred until at least after the second shock has been delivered.”

Abstract 1
Objective: To describe temporal trends in the time interval between first and second attempts at defibrillation and the association between this time interval and outcomes in patients with persistent ventricular tachycardia or ventricular fibrillation (VT/VF) arrest in hospital.
Design: Retrospective cohort study
Setting: 172 hospitals in the United States participating in the Get With The Guidelines-Resuscitation registry, 2004-12.
Participants Adults who received a second defibrillation attempt for persistent VT/VF arrest within three minutes of a first attempt.
Interventions: Second defibrillation attempts categorized as early (time interval of up to and including one minute between first and second defibrillation attempts) or deferred (time interval of more than one minute between first and second defibrillation attempts).
Main outcome measure: Survival to hospital discharge.
Results: Among 2733 patients with persistent VT/VF after the first defibrillation attempt, 1121 (41%) received a deferred second attempt. Deferred second defibrillation for persistent VT/VF increased from 26% in 2004 to 57% in 2012 (P Conclusions: Since 2004, the use of deferred second defibrillation for persistent VT/VF in hospital has doubled. Deferred second defibrillation was not associated with improved survival.

Abstract 2
Objectives: To evaluate whether patients who experience cardiac arrest in hospital receive epinephrine (adrenaline) within the two minutes after the first defibrillation (contrary to American Heart Association guidelines) and to evaluate the association between early administration of epinephrine and outcomes in this population.
Design: Prospective observational cohort study.
Setting Analysis of data from the Get With The Guidelines-Resuscitation registry, which includes data from more than 300 hospitals in the United States.
Participants: Adults in hospital who experienced cardiac arrest with an initial shockable rhythm, including patients who had a first defibrillation within two minutes of the cardiac arrest and who remained in a shockable rhythm after defibrillation.
Intervention: Epinephrine given within two minutes after the first defibrillation.
Main outcome measures: Survival to hospital discharge. Secondary outcomes included return of spontaneous circulation and survival to hospital discharge with a good functional outcome. A propensity score was calculated for the receipt of epinephrine within two minutes after the first defibrillation, based on multiple characteristics of patients, events, and hospitals. Patients who received epinephrine at either zero, one, or two minutes after the first defibrillation were then matched on the propensity score with patients who were “at risk” of receiving epinephrine within the same minute but who did not receive it.
Results: 2978patients were matched on the propensity score, and the groups were well balanced. 1510 (51%) patients received epinephrine within two minutes after the first defibrillation, which is contrary to current American Heart Association guidelines. Epinephrine given within the first two minutes after the first defibrillation was associated with decreased odds of survival in the propensity score matched analysis (odds ratio 0.70, 95% confidence interval 0.59 to 0.82; P<0.001). Early epinephrine administration was also associated with a decreased odds of return of spontaneous circulation (0.71, 0.60 to 0.83; P<0.001) and good functional outcome (0.69, 0.58 to 0.83; P<0.001).
Conclusion: Half of patients with a persistent shockable rhythm received epinephrine within two minutes after the first defibrillation, contrary to current American Heart Association guidelines. The receipt of epinephrine within two minutes after the first defibrillation was associated with decreased odds of survival to hospital discharge as well as decreased odds of return of spontaneous circulation and survival to hospital discharge with a good functional outcome.

BMJ material
BMJ abstract 1
BMJ abstract 2


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