Elsevier

Resuscitation

Volume 49, Issue 1, April 2001, Pages 9-14
Resuscitation

Patient outcomes following defibrillation with a low energy biphasic truncated exponential waveform in out-of-hospital cardiac arrest

https://doi.org/10.1016/S0300-9572(00)00338-5Get rights and content

Abstract

Primary objective: To determine the outcome of patients with out-of-hospital cardiac arrest and ventricular fibrillation as the presenting rhythm while using automated external defibrillators (AEDs) that delivered non-escalating, impedance-compensated low-energy (150 J) shocks. Materials and methods: AEDs delivering low-energy biphasic truncated exponential (BTE) shocks were employed in an emergency medical services (EMS) system in which first-arriving personnel — police, firefighters or paramedics — delivered the initial shocks. Patients were classified according to their response to shocks: restoration of sustained spontaneous circulation (ROSC) without need for epinephrine and other advanced life support (ALS) interventions; and ALS, those requiring epinephrine in all instances. The primary end-point was neurologically-intact discharge survival. Secondary end-points were ROSC with shocks only and the call-to-shock time interval. Results: Of 42 patients with VF arrest treated with BTE shocks, 35 were bystander-witnessed. Of these 35, 14 (38%) regained a sustained ROSC on-scene with shocks only, needing no epinephrine for ROSC. All 14 survived to discharge home. Of the remaining 21 patients needing ALS intervention, only two (9.5%) survived to discharge. Overall, 16/35 patients (46%) survived to discharge home, an outcome comparable to our experience with patients treated with escalating high-energy monophasic waveform shocks. Conclusions: Low-energy (150 J) non-escalating biphasic truncated exponential waveform shocks terminate VF in out-of-hospital cardiac arrest with high efficacy; patient outcome is comparable with that observed with escalating high-energy monophasic shocks. Low-energy shocks, in addition to high efficacy, may confer the advantage of less shock-induced myocardial dysfunction, though this will be difficult to define in the clinical circumstance of long-duration VF provoked by a pre-existing diseased myocardial substrate.

Zusammenfassung

Objectivo primário: Determinar o prognóstico de vı́timas de paragem cardı́aca com ritmo inicial de fibrilhação ventricular, utilizando desfibrilhadores automáticos externos (DAEs) que fornecem choques de baixa energia (150 J) ajustáveis para a impedância. Material e métodos: Num sistema de emergência médica (SEM) foram utilizados DAEs bifásicos de baixa energia fornecendo choques com curva exponencial (BTE), pelos profissionais que mais rapidamente acorrem ao local – polı́cias, bombeiros, ou paramédicos. Os doentes foram classificados em função da primeira resposta á desfibrilhação: Recuperação de circulação espontânea (ROSC) sem necessidade de recurso a adrenalina ou outra intervenção de suporte avançado de vida (SAV); e outro com necessidade de SAV, incluindo recurso a adrenalina em todos os casos. O critério principal de avaliação foi a alta hospitalar sem seqüelas neurológicas. Outros critérios avaliados foram a ROSC apenas com recurso á desfibrilhação e o intervalo entre a chamada do SEM e o 1° choque. Resultados: Das 42 vı́timas tratadas com choques com BTE, 35 tiveram paragens testemunhadas. Destes 35, 14 (38%) tiveram ROSC sustentada no local da paragem apenas com recurso á desfibrilhação, não necessitando de adrenalina. Todos tiveram alta hospitalar. Dos 21 restantes que necessitaram de SAV, apenas dois (9,5%) sobreviveram até terem alta hospitalar. Globalmente16/35 (46%) tiveram alta hospitalar, resultados comparáveis á nossa experiência recorrendo a aparelhos que utilizam choques monofásicos de alta energia. Conclusões: Os DAEs bifásicos de baixa energia (150 J) fornecendo choques com curva exponencial recuperaram a FV em vı́timas de paragem cardiorespiratória em ambiente pré-hospitalar, de forma muito eficaz. Os resultados foram comparáveis aos obtidos com aparelhos monofásicos Os choques com baixa energia, para além da grande eficácia, podem ter a vantagem de provocar menos lesões miocárdicas, apesar deste ser um parâmetro dificilmente mensurável em condições em que ocorrem FV prolongadas, num terreno em que já podem existir lesões miocárdicas prévias.

Introduction

In several previous publications, we have reported our experience with community-wide early defibrillation employing a dual police/paramedic response [1], [2], [3], [4], [5]. Our primary end-point in two of these studies was patient outcome, with secondary outcomes of call-to-shock time interval and restoration of spontaneous circulation with shocks only (ROSC patients), as opposed to those who needed advanced life support interventions (ALS patients). In one of these reports, we described the evolution of post-defibrillation cardiac rhythms in patients treated with monophasic damped sine (MDS) shocks and those defibrillated with impedance-compensated biphasic truncated exponential (BTE) shocks [4]. In December 1996, we introduced BTE waveform automated external defibrillators (AEDs) into our early defibrillation program and in 1997 reported our early experience with this waveform in the termination of ventricular fibrillation (VF) in ten patients with long-duration VF, only five of whom had sustained a witnessed arrest [5]. The purpose of this report is to present our experience with patient outcome in witnessed VF arrest after the introduction of defibrillation with this non-escalating low-energy waveform.

Section snippets

Materials and methods

We have described our materials and methods in detail [1], [2], [3], [4], [5]. In December 1996, 12 BTE AEDs (ForeRunner®, Agilent Technologies/Heartstream Operation, Seattle, WA) were placed in police cars and four in ambulances. In early 1998, the ambulance AEDs were transferred to fire vehicles and two additional units were placed in these vehicles, thus making 18 BTE AEDs available in police cars and fire vehicles. During the BTE AED study period, the population and area of the city

Results

During the study period, 42 patients in VF when first encountered by police, firefighters or paramedics were treated with BTE shocks. Of the 42 patients, 31 (74%) regained a sustained spontaneous circulation on-scene and 16/42 (38%) survived to discharge. Four patients were outside the City of Rochester, but within the area for which our emergency medical services (EMS) system is the ALS response. In these communities, the same BTE AED was used by first responders. Of the 42 patients with VF,

Discussion

While we have shown in previous publications [4], [5], [6], [8] a high rate of termination of VF with non-escalating low-energy shocks (150 J), patient outcome data have not been assessed rigorously in our EMS system since deployment of this waveform. Our program has provided an opportunity to assess patient outcome after defibrillation with low-energy BTE shocks and to retrospectively compare patient outcomes in patients treated with escalating high-energy MDS shocks. The results indicate that

Conclusions

These data indicate that our high rates of discharge survival over several years’ experience with rapid defibrillation in a community-wide setting were sustained when non-escalating low-energy BTE waveform shocks were deployed. Defibrillation was achieved with high-efficacy even in the presence of long-standing underlying coronary heart disease with previous CABG and/or PTCA, valvular heart disease and dilated cardiomyopathy. If energy-related myocardial dysfunction has clinical relevance, then

Acknowledgements

We thank Kimberly Sankey for assistance with the manuscript; City of Rochester Police and Fire Departments; Gold Cross Ambulance Service; and law enforcement and ambulance dispatch personnel.

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