Abstract 52: Comparison of Serial Monophasic and Biphasic Shocks in Out-of-Hospital Cardiac Arrest
Survival rates in sudden cardiac death (SCD) depend on initially registered arrhythmia, ventricular fibrillation (VF) having the best prognosis. The optimal energy for defibrillation, discharge characteristic of shock, and time point for shock application in patients (pts) with a prolonged down time in out-of-hospital SCD is under discussion.
Methods: Data from the 2-tiered Berlin EMS were analyzed. LP300 monophasic (MON) and LP500 biphasic (BI) defibrillators (Physio Control Corp.) were used by the 1st tier. Shock series of three consecutive shocks each (200, 200, 360J MON and 150, 200, 360J BI) followed by 360J shocks each were delivered if appropriate. The information on rhythm and voices being stored in the AED devices was manually reviewed. Rhythm analysis was performed immediately before and 5sec after each shock.
Results: Of 1700 pts with SCD in in 447 (26%) the initial rhythm was VF. These pts received at least one shock by the AED (MON n=223, BI n=224). VF was terminated by BI vs. MON shocks in 74% vs. 66% after the first, in 76% vs. 52% after the second, in 68% vs. 44% after the third shock, respectively. A fourth shock delivered after three minutes of intermittent CPR terminated VF in 83% (19 of 26 pts) with BI but in only 48% (15 of 31 pts, p=0.058) with MON. A coordinated rhythm (CR) was achieved in 25% of pts after each shock with MON and BI. Also the proportion of pts relapsing into VF from CR or asystole was 40% with MON and BI after each shock.
Conclusion: While the VF termination rate of consecutive BI shocks of increasing energy in pts with out-of-hospital SCD is constant it decreases with MON shocks. Moreover the efficacy of BI remains at least stable after intermittent CPR whereas further decreases with MON. However, in our series with BI shocks, though slightly superior to MON shocks, the rate of VF termination was lower than reported in earlier studies.