- Email: [email protected]
The guidelines got it right on defibrillation energy protocol
Resuscitation 80 (2009) 1438–1441
Contents lists available at ScienceDirect
Resuscitation journal homepage: www.elsevier.com/locate/resuscitation
Letters to the Editor The guidelines got it right on defibrillation energy protocol Sir, We welcome the interesting data by Walker et al.1 on the question of whether impedance is reduced by successive biphasic defibrillator shocks. The paper confirms our observation that there is no such effect with biphasic technology and supports our conclusion, published in these pages,2 that impedance no longer plays a role in resuscitation outcomes. The authors also present persuasive data that a failed first shock identifies a population of difficult patients for whom a second shock is less likely to be successful. The authors conclude that “. . .the true benefit to be derived from the practices of stacking shocks and delivering second shocks at the same energy as failed first shocks are likely to be less than expected.” We agree, but note that our observations suggest this patient population may be equally refractory to a same-energy shock protocol and an escalating-shock protocol. The study’s data does not support any advantage of escalated energy in this challenging population. Only five patients who failed the first 200 J shock received a second shock at the same 200 J dosage. Two converted; a 95% confidence interval of 5–85% for efficacy. Of the 56 who received an escalating 300 J shock, 39 converted on the second shock (70%), for a 56–81% confidence interval for efficacy. Hence, one cannot reject a null hypothesis of no difference in the performance of these two protocols for patients failing the first shock. Three studies of non-escalated 150 J shocks,3–5 collectively report a second-shock success rate of 79% (15/19, CI 54–95%) for patients with failed first shocks. While not the controlled study required to definitively address this issue, these results are on the whole statistically indistinguishable from those with escalation in the Walker study. Ironically, the high first-shock success rate with biphasic defibrillation makes study of therapy after a failed first shock particularly difficult. In the three studies mentioned above,3–5 first-shock efficacy for the non-escalated 150 J biphasic was 92% (93/101). The Hess study3 published all-shock success rate, which was 91% (233/257). These results are statistically equivalent to Walker’s 93% first-shock efficacy and 90% all-shock efficacy (escalating to 360 J in many cases). The ERC guidelines state that “with biphasic defibrillators there is no evidence to support either a fixed or escalating energy protocol,” and the Walker study does not change this. It remains true, as the AHA guidelines state, that “it is not possible to make a definitive recommendation for the selected energy for the first or subsequent biphasic defibrillation attempts. . . . The ideal shock dose for a biphasic device is one that falls within the range that has been documented to be effective using that specific device. . . . For second and subsequent biphasic shocks, use the same or higher energy (Class IIa).”
0300-9572/$ – see front matter © 2009 Elsevier Ireland Ltd. All rights reserved.
Scientifically designed and proven biphasic therapies work well, but there are significant technical differences among manufacturers. The authors emphasize that they evaluated one specific device. We reinforce caution to your readers about generalizing results from one specific therapy to others. Conflict of interest statement All authors are employees of Philips Healthcare, a manufacturer of defibrillators. References 1. Walker RG, Koster RW, Sun C, et al. Defibrillation probability and impedance change between shocks during resuscitation from out-of-hospital cardiac arrest. Resuscitation 2009;80:773–7. 2. White RD, Blackwell TH, Russell JK, Snyder DE, Jorgenson DB. Transthoracic impedance does not affect defibrillation, resuscitation or survival in patients with out-of-hospital cardiac arrest treated with a non-escalating biphasic waveform defibrillator. Resuscitation 2005;64:63–9. 3. Hess EP, Russell JK, Liu PY, White RD. A high peak current 150-J fixed-energy defibrillation protocol treats recurrent ventricular fibrillation (VF) as effectively as initial VF. Resuscitation 2008;79:28–33. 4. Capucci A, Aschieri D, Piepoli MF, et al. Tripling survival from sudden cardiac arrest via early defibrillation without traditional education in cardiopulmonary resuscitation. Circulation 2002;106:1065–70. 5. Schneider T, Martens PR, Paschen H, et al. Multicenter, randomized, controlled trial of 150-J biphasic shocks compared with 200- to 360-J monophasic shocks in the resuscitation of out-of-hospital cardiac arrest victims. Optimized Response to Cardiac Arrest (ORCA) Investigators. Circulation 2000;102:1780–7.
James K. Russell ∗ Dawn Jorgenson Marc Fuller Philips Healthcare, Seattle, WA 98121, United States ∗ Corresponding
author at: Philips Healthcare, Emergency Care, 2301 Fifth Ave., Suite 200, Seattle, WA 98121, United States. Tel.: +1 206 664 2038; fax: +1 206 664 2070. E-mail address:[email protected] (J.K. Russell) 4 August 2009
doi:10.1016/j.resuscitation.2009.08.028
Reply to Letter: The guidelines got it right on defibrillation energy protocol Sir, We thank Russell et al. for their comments, and appreciate the opportunity to further clarify how the findings of our study1 relate to defibrillation energy protocols. The rationale for non-escalation of a second shock for defibrillation in cardiac arrest was based on an assumption that a first shock
Contents lists available at ScienceDirect
Resuscitation journal homepage: www.elsevier.com/locate/resuscitation
Letters to the Editor The guidelines got it right on defibrillation energy protocol Sir, We welcome the interesting data by Walker et al.1 on the question of whether impedance is reduced by successive biphasic defibrillator shocks. The paper confirms our observation that there is no such effect with biphasic technology and supports our conclusion, published in these pages,2 that impedance no longer plays a role in resuscitation outcomes. The authors also present persuasive data that a failed first shock identifies a population of difficult patients for whom a second shock is less likely to be successful. The authors conclude that “. . .the true benefit to be derived from the practices of stacking shocks and delivering second shocks at the same energy as failed first shocks are likely to be less than expected.” We agree, but note that our observations suggest this patient population may be equally refractory to a same-energy shock protocol and an escalating-shock protocol. The study’s data does not support any advantage of escalated energy in this challenging population. Only five patients who failed the first 200 J shock received a second shock at the same 200 J dosage. Two converted; a 95% confidence interval of 5–85% for efficacy. Of the 56 who received an escalating 300 J shock, 39 converted on the second shock (70%), for a 56–81% confidence interval for efficacy. Hence, one cannot reject a null hypothesis of no difference in the performance of these two protocols for patients failing the first shock. Three studies of non-escalated 150 J shocks,3–5 collectively report a second-shock success rate of 79% (15/19, CI 54–95%) for patients with failed first shocks. While not the controlled study required to definitively address this issue, these results are on the whole statistically indistinguishable from those with escalation in the Walker study. Ironically, the high first-shock success rate with biphasic defibrillation makes study of therapy after a failed first shock particularly difficult. In the three studies mentioned above,3–5 first-shock efficacy for the non-escalated 150 J biphasic was 92% (93/101). The Hess study3 published all-shock success rate, which was 91% (233/257). These results are statistically equivalent to Walker’s 93% first-shock efficacy and 90% all-shock efficacy (escalating to 360 J in many cases). The ERC guidelines state that “with biphasic defibrillators there is no evidence to support either a fixed or escalating energy protocol,” and the Walker study does not change this. It remains true, as the AHA guidelines state, that “it is not possible to make a definitive recommendation for the selected energy for the first or subsequent biphasic defibrillation attempts. . . . The ideal shock dose for a biphasic device is one that falls within the range that has been documented to be effective using that specific device. . . . For second and subsequent biphasic shocks, use the same or higher energy (Class IIa).”
0300-9572/$ – see front matter © 2009 Elsevier Ireland Ltd. All rights reserved.
Scientifically designed and proven biphasic therapies work well, but there are significant technical differences among manufacturers. The authors emphasize that they evaluated one specific device. We reinforce caution to your readers about generalizing results from one specific therapy to others. Conflict of interest statement All authors are employees of Philips Healthcare, a manufacturer of defibrillators. References 1. Walker RG, Koster RW, Sun C, et al. Defibrillation probability and impedance change between shocks during resuscitation from out-of-hospital cardiac arrest. Resuscitation 2009;80:773–7. 2. White RD, Blackwell TH, Russell JK, Snyder DE, Jorgenson DB. Transthoracic impedance does not affect defibrillation, resuscitation or survival in patients with out-of-hospital cardiac arrest treated with a non-escalating biphasic waveform defibrillator. Resuscitation 2005;64:63–9. 3. Hess EP, Russell JK, Liu PY, White RD. A high peak current 150-J fixed-energy defibrillation protocol treats recurrent ventricular fibrillation (VF) as effectively as initial VF. Resuscitation 2008;79:28–33. 4. Capucci A, Aschieri D, Piepoli MF, et al. Tripling survival from sudden cardiac arrest via early defibrillation without traditional education in cardiopulmonary resuscitation. Circulation 2002;106:1065–70. 5. Schneider T, Martens PR, Paschen H, et al. Multicenter, randomized, controlled trial of 150-J biphasic shocks compared with 200- to 360-J monophasic shocks in the resuscitation of out-of-hospital cardiac arrest victims. Optimized Response to Cardiac Arrest (ORCA) Investigators. Circulation 2000;102:1780–7.
James K. Russell ∗ Dawn Jorgenson Marc Fuller Philips Healthcare, Seattle, WA 98121, United States ∗ Corresponding
author at: Philips Healthcare, Emergency Care, 2301 Fifth Ave., Suite 200, Seattle, WA 98121, United States. Tel.: +1 206 664 2038; fax: +1 206 664 2070. E-mail address:[email protected] (J.K. Russell) 4 August 2009
doi:10.1016/j.resuscitation.2009.08.028
Reply to Letter: The guidelines got it right on defibrillation energy protocol Sir, We thank Russell et al. for their comments, and appreciate the opportunity to further clarify how the findings of our study1 relate to defibrillation energy protocols. The rationale for non-escalation of a second shock for defibrillation in cardiac arrest was based on an assumption that a first shock