Retrospective evaluation of current-based impedance compensation defibrillation in out-of-hospital cardiac arrest

Survival to hospital discharge with biphasic fixed 360 joules versus 200 escalating to 360 joules defibrillation strategies in out-of-hospital cardiac arrest of presumed cardiac etiology

INTRODUCTION

Guidelines recommend constant or escalating energy levels for shocks after the initial defibrillation attempt. Studies comparing survival to hospital discharge with escalating vs fixed high energy level shocks are lacking. We compared survival to hospital discharge for 200 J escalating to 360 J vs fixed 360 J in patients with initial ventricular fibrillation/pulseless ventricular tachycardia in a post-hoc analysis of the Circulation Improving Resuscitation Care trial database.

METHODS AND RESULTS

Pre-shock rhythm, rhythm 5 s after shock, shock energy levels, termination of ventricular fibrillation/pulseless ventricular tachycardia (TOF), and survival to hospital discharge were recorded. Association between defibrillation strategy and survival to hospital discharge was investigated with multivariable logistic regression. The escalating energy group included 260 patients and 883 shocks vs 478 patients and 1736 shocks in the fixed-high energy group. There was no difference in survival to hospital discharge between escalating (70/255 patients, 28%) and fixed energy group (132/478 patients, 28%) (unadjusted OR 1.00, 95% CI 0.72-1.42 and adjusted OR 0.81, 95% CI 0.54-1.22, p = 0.32). First shock TOF was 86% in the escalating group compared to 83% in the fixed-high group, p = 0.27.

CONCLUSION

There was no difference in survival to hospital discharge or the frequency of TOF between escalating energy and fixed-high energy group. ClinicalTrials.gov Identifier: NCT00597207.

Use of double sequential external defibrillation for refractory ventricular fibrillation during out-of-hospital cardiac arrest

INTRODUCTION

Survival from out of hospital cardiac arrest (OHCA) is highest in victims with shockable rhythms when early CPR and rapid defibrillation are provided. However, a subset of individuals present with ventricular fibrillation (VF) that does not respond to defibrillation (refractory VF). One intervention that may be a possible option in refractory VF is double sequential external defibrillation (DSD). The objective of this case series was to describe the outcome of prehospital victims with refractory VF treated with DSD in the out-of-hospital setting.

METHODS

This evaluation is a retrospective chart review of VF patients treated with DSD in the prehospital setting from August 1st, 2010 through June 30th, 2014. Patients were excluded if less than 17 years of age. The outcomes we evaluated were the number of patients with return of spontaneous circulation, conversion from VF, survival-to-hospital discharge, and Cerebral Performance Category score.

RESULTS

Total of 2428 OHCA events were reviewed with twelve patients treated with DSD. Median DSD and prehospital resuscitation times were 27min (IQR 22-33) and 32 (IQR 24-38), respectively. Of the 12 patients treated, return of spontaneous circulation was achieved in three patients, nine patients were converted out of ventricular fibrillation, three patients survived to hospital discharge, and two patients (2/12, 17%) were discharged with Cerebral Performance Category scores of 1 (good cerebral performance).

CONCLUSIONS

Double sequential defibrillation may be another tool to improve neurologically intact survival from OHCA. Further studies are needed to demonstrate direct benefits to patient outcomes.

Electrical features of eighteen automated external defibrillators: a systematic evaluation

AIM

Assessment and comparison of the electrical parameters (energy, current, first and second phase waveform duration) among eighteen AEDs.

METHOD

Engineering bench tests for a descriptive systematic evaluation in commercially available AEDs. AEDs were tested through an ECG simulator, an impedance simulator, an oscilloscope and a measuring device detecting energy delivered, peak and average current, and duration of first and second phase of the biphasic waveforms. All tests were performed at the engineering facility of the Lombardia Regional Emergency Service (AREU).

RESULTS

Large variations in the energy delivered at the first shock were observed. The trend of current highlighted a progressive decline concurrent with the increases of impedance. First and second phase duration varied substantially among the AEDs using the exponential biphasic waveform, unlike rectilinear waveform AEDs in which phase duration remained relatively constant.

CONCLUSIONS

There is a large variability in the electrical features of the AEDs tested. Energy is likely not to be the best indicator for strength dose selection. Current and shock duration should be both considered when approaching the technical features of AEDs. These findings may prompt further investigations to define the optimal current and duration of the shock waves to increase the success rate in the clinical setting.