Every Second Counts When Performing CPR

Michael's Hospital (Toronto, Canada) and the University of Toronto (Canada) examined the files of 815 patients who suffered an out-of-hospital cardiac arrest between December 2005 and June 2007. The data was gathered by the Resuscitation Outcomes Consortium (ROC), a group of 11 Canadian and US regional clinical centers, including more than 200 agencies that carry out research related to cardiac arrest resuscitation and life-threatening traumatic injury. The patients were treated with either an automated external defibrillator (AED) or a manual defibrillator.

The researchers found the odds of surviving until hospital discharge were significantly lower for patients whose rescuers paused CPR for 20 seconds or more before delivering a shock (the preshock pause), and for patients whose rescuers paused CPR before and then after defibrillation (the peri-shock pause) for 40 seconds or more. The researchers also found that patients with peri-shock pauses of more than 40 seconds had a 45% decrease in survival when compared to those who had peri-shock pauses of less than 20 seconds. In all, the researchers found an 18% drop in the number of patients surviving to be discharged from hospital for every five-second increase in the pause between CPR and providing a shock with a defibrillator. The study was published in the June 20, 2011, issue of Circulation.

"We found that if the interval between ending CPR and delivering a shock was over 20 seconds, the chance of a patient surviving was 53% less than if that interval was less than 10 seconds," said lead author Sheldon Cheskes, MD, an assistant professor of emergency medicine at the University of Toronto. "Interestingly there was no significant association between the time from delivering a shock to restarting CPR, known as the post-shock pause, and survival to discharge. This led us to believe that a primary driver for survival was related to the preshock pause interval."

Based on the results of the study, the researchers recommend that paramedics should minimize all CPR interruptions, and preferably defibrillate patients in manual mode to limit the preshock pause to an "optimal time" of five seconds. Additionally, AED manufacturers should modify defibrillator software to quicken the assessment of a patient's heart rhythm, and allow devices to deliver more timely shocks while in AED mode.

Related Links:
St. Michael's Hospital
University of Toronto