Literature Review: CPR Before Defibrillation

Winship C, Williams B, Boyle MJ. Cardiopulmonary resuscitation before defibrillation in the out-of-hospital setting: a literature review. Emerg Med J, 2012 Oct; 29(10): 826–9.

Abstract

Background—Many studies over the past decade have investigated delaying initial defibrillation to perform cardiopulmonary resuscitation (CPR), as it has been associated with increased rates of restoration of spontaneous circulation and/or survival. Since 2006, a number of studies have investigated these procedures. The objective of this study was to undertake a literature review examining the commencement of CPR before defibrillation in the out-of-hospital setting. Methods—A literature review was undertaken using the electronic medical databases Ovid Medline, EMBASE, CINHAL Plus, Cochrane Systematic Review and Meditext, from their commencement to the end of June 2011. Keywords used in the search included: CPR, defibrillation, ventricular fibrillation, VF, EMS, EMT, paramedic, emergency medical service, emergency medical technician, prehospital, out-of-hospital and ambulance. References of relevant articles were also reviewed.

Findings—Of the 3,079 articles located, 10 met the inclusion criteria. These studies showed conflicting results. All retrospective studies (n=6) indicated a benefit in performing pre-shock CPR on patients with ventricular fibrillation for durations between 90–180 seconds. Conversely, all randomized controlled trials demonstrated no benefit from providing CPR before defibrillation compared with immediate defibrillation for return of spontaneous circulation, neurological outcome and/or survival to hospital discharge. However, none of the studies reported evidence that CPR before defibrillation is harmful. Conclusion—Conflicting evidence remains regarding the benefit of CPR before defibrillation. The establishment of a consistent time frame of chest compressions before defibrillation in the out-of-hospital setting will provide uniformity in standards in clinical practice and education and training.

Comment

High-quality CPR increases survival rates from cardiac arrest. However, it is not clear whether CPR is helpful in the interval between EMS arrival and the first defibrillation. This practice was originally based on a 1999 observational trial, where the authors looked at the effect of a system-wide change in protocol from “immediate defibrillation” to “90 seconds of CPR before defibrillation.” They found that in those patients with dispatch-to-arrival-on-scene intervals greater than 4 minutes, patients in the CPR-first group were more likely to survive. The hypothesis is that circulation to the myocardial cells will improve their metabolic state and make them better able to respond to a shock and return to a normal rhythm. The 2005 AHA CPR Guidelines stated, “EMS rescuers may give about 5 cycles (about 2 minutes) of CPR before attempting defibrillation…when the EMS response (call-to-arrival) interval is greater than 4 to 5 minutes.”

However, later randomized controlled trials have not shown CPR before defibrillation to be beneficial, and the large Resuscitation Outcomes Consortium trial showed no difference between 30–60 seconds and 3 minutes of CPR before defibrillation. The practice has been deemphasized in the AHA 2010 CPR Guidelines. We do not have all the answers yet. It may be that in very prolonged arrests, longer CPR before defibrillation is beneficial, but that has not yet been shown. Until then a reasonable approach would be to provide immediate high-quality CPR while setting up the AED or monitor/defibrillator, then stop CPR to immediately analyze and defibrillate.

Angelo Salvucci, Jr., MD, FACEP, is medical director for the Santa Barbara County and Ventura County (CA) EMS agencies and a member of the EMS World editorial advisory board.