Defibrillation probability and impedance change between shocks during resuscitation from out-of-hospital cardiac arrest

More ups and fewer downs in optimal biphasic defibrillation strategies

“…This was based on studies showing that an escalating strategy reduces the number of shocks required to restore an organised rhythm compared with fixed-dose biphasic defibrillation, although rates of return of spontaneous circulation (ROSC) or survival to hospital discharge were not significantly different. 10,11 This study reported a cumulative three-shock success rate of 97.8%, similar to that reported by the same author using a fixed 150 J BTE waveform for the three initial shocks. 9 While the possible benefits of an escalating strategy remain to be determined, it would appear that the rush not to reprogramme automatic defibrillators delivering a fixed-dose strategy is justified, based on the high three-shock conversion rates now documented in a second study.…”

Analysis of transthoracic impedance during real cardiac arrest defibrillation attempts in older children and adolescents: Are stacked-shocks appropriate?

“…14,16,17 Nevertheless, other animal and adult human data have shown that TTI may not decrease after a defibrillation attempt. 7,26,28 The largest adult study evaluating TTI after 863 defibrillator shocks demonstrated that the TTI is nearly as likely to increase as decrease after a first shock for out-of-hospital cardiac arrests. 7 The authors noted that the lack of consistent decreases in TTI post-shock may have been partly due to the prolonged duration of cardiac arrest in the out-of-hospital, because prolonged poor cutaneous blood flow may have precluded the post-shock hyperemia purported to decrease the TTI.…”

“…16–25 There is conflicting animal and adult evidence whether TTI significantly decreases after shocks 7,16,26–28 and whether this makes a clinical difference in termination of fibrillation outcomes. 29–31 In 2005, the AHA changed recommendations to treat ventricular fibrillation from three transthoracic stacked-shocks to one shock followed by immediate chest compressions because biphasic shocks were approximately 90% effective at terminating fibrillation and therefore providing uninterrupted perfusion post-shock is more important than further shocks.…”

Advances in defibrillation

“…Since then, studies using an escalating-energy protocol have shown a reduction in the number of shocks required to restore an organized rhythm, and demonstrated that higher energy levels may be needed for successful defibrillation [12,13]. However, rates of return of spontaneous circulation or survival to hospital discharge were no different between strategies [14,15].…”

“…The 200, 200 and 360 J sequence, therefore, was thought to result in an increased transmyocardial current with each shock. Studies in both adults [13,20] and children [21] using biphasic waveforms have shown that the magnitude of any decrease in TTI with sequential shocks is so minimal as to make no significant clinical difference.…”