Double Sequential External Defibrillation Research Articles

Resuscitation Update - What's New?

Perfect, uninterrupted basic life support (BLS) is the key for successful cardiopulmonary resuscitation (CPR) in out-of-hospital cardiac arrest (OHCA). Time plays an important role in the treatment of OHCA. This applies both to the time until the start of BLS and the reduction of all pauses during resuscitation, especially chest compressions. In 2022, the rate of bystander-CPR showed an absolute increase of 4% compared to previous years. The bystander-CPR rate is currently above 50%. Compared to OHCA in adults, cardiac arrest in children is rare in Germany. In the period from 2007 to 2021, the incidence was 3.08 per 100000 children. In addition, the etiology in children varies depending on the age group. While hypoxia is often the cause of circulatory arrest in younger children, trauma and drowning accidents are the main causes in school-age children. Different additional diagnostic and therapeutic strategies have been evaluated over the last years. Point-of-care ultrasound during resuscitation should only be performed by experienced users. Interrupting chest compressions and thus prolonging the no-flow phases must be avoided. Double sequential external defibrillation after the third shock can successfully terminate refractory ventricular fibrillation. While further studies are needed, emergency medical systems should train their teams to avoid complications. In refractory OHCA, extracorporeal CPR should be considered. In the case of in-hospital cannulation, immediate transport should be weighed against impaired chest compression quality. Therefore, transportation under CPR is only beneficial if there is an indication for further treatment.

The impact of alternate defibrillation strategies on shock-refractory and recurrent ventricular fibrillation: A secondary analysis of the DOSE VF cluster randomized controlled trial

BackgroundThe DOSE VF randomized controlled trial (RCT) employed a pragmatic definition of refractory ventricular fibrillation (VF after three successive shocks). However, it remains unclear whether the underlying rhythm during the first three shocks was shock-refractory or recurrent VF. ObjectiveTo explore the relationship between alternate defibrillation strategies employed during the DOSE VF RCT and the type of VF, either shock-refractory VF or recurrent VF, on patient outcomes. MethodsWe performed a secondary analysis of the DOSE VF RCT. We categorized cases as shock-refractory or recurrent VF based on pre-randomization shocks (shocks 1–3). We then analyzed all subsequent (post-randomization) shocks to assess the impact of standard, vector change (VC) or double sequential external defibrillation (DSED) shocks on clinical outcomes employing logistic regression adjusted for Utstein variables, antiarrhythmics, and epinephrine. ResultsWe included 345 patients; 60 (17%) shock-refractory VF, and 285 (83%) recurrent VF. Patients in recurrent VF had greater survival than shock-refractory VF (OR: 2.76 95% CI [1.04, 7.27]). DSED was superior to standard defibrillation for survival overall, and for patients with shock-refractory VF (28.6% vs 0%, p = 0.041) but not for those in recurrent VF. DSED was superior to standard defibrillation for return of spontaneous circulation (ROSC) and neurologic survival for shock-refractory and recurrent VF. VC defibrillation was not superior for survival or ROSC overall, for shock-refractory, or recurrent VF groups, but was superior for VF termination across all groups. ConclusionDSED appears to be the superior defibrillation strategy in the DOSE VF trial, irrespective of whether the preceding VF is shock-refractory or recurrent.

Association of coronary angiography with ST-elevation and no ST-elevation in patients with refractory ventricular fibrillation – A substudy of the DOuble SEquential External Defibrillation for Refractory Ventricular Fibrillation (DOSE-VF randomized control trial)

BackgroundRefractory ventricular fibrillation or pulseless ventricular tachycardia (rVF/pVT) during out-of-hospital cardiac arrest (OHCA) is associated with poor survival. Double sequential defibrillation (DSED) and vector change (VC) improved survival for rVF/pVT in the DOSE-VF RCT. However, the role of angiography and percutaneous coronary intervention (angiography/PCI) during the trial is unknown. ObjectivesTo determine the incidence of ST-elevation (STE) and no ST-elevation (NO-STE) on post-arrest ECG and the use of angiography/PCI in patients with rVF/pVT during the DOSE-VF RCT. MethodAdults (≥18-years) with rVF/pVT OHCA randomized in the DOSE-VF RCT who survived to hospital admission were included. The primary analysis compared the proportion of angiography in STE and NO-STE. We performed regression modelling to examine association between STE, the interaction with defibrillation strategy, and survival to discharge controlling for known covariates. ResultsWe included 151 patients, 74 (49%) with STE and 77 (51%) with NO-STE. The proportion of angiography was higher in the STE cohort than NO-STE (87.8% vs 44.2%, p < 0.001); similarly the proportion of PCI was also higher (75.7% vs 9.1%, p < 0.001). Survival to discharge was similar between STE and NO-STE (63.5% vs 51.9%, p = 0.15). Use of angiography/PCI did not differ between defibrillation strategies. Decreased age (OR 0.95, 95% CI 0.92–0.98; p = 0.001) and angiography (OR 9.33, 95% CI 3.60–26.94; p < 0.001) were predictors of survival; however, STE was not. ConclusionWe found high rates of angiography/PCI in patients with STE compared to NO-STE, however similar rates of survival. Angiography was an independent predictor of survival. Improved rates of survival employing DSED and VC were independent of angiography/PCI.

The impact of double sequential shock timing on outcomes during refractory out-of-hospital cardiac arrest

BackgroundAnimal studies suggest the efficacy of double sequential external defibrillation (DSED) may depend on the interval between the two shocks, or “DSED interval”. No human studies have examined this concept. ObjectivesTo determine the relationship between DSED interval and termination of ventricular fibrillation (VFT), return of spontaneous circulation (ROSC), survival to hospital discharge, and favourable neurological status (MRS ≤ 2) for patients in refractory VF. MethodsWe performed a retrospective review of adult (≥18 years) out-of-hospital cardiac arrest between January 2015 and May 2022 with refractory VF who received ≥1 DSED shock. DSED interval was divided into four pre-defined categories. We examined the association between DSED interval and patient outcomes using general estimated equation logistic regression or Fisher's exact test. ResultsAmong 106 included patients, 303 DSED shocks were delivered (median 2, IQR 1–3). DSED intervals of 75–125 ms (OR 0.39, 95% CI 0.16–0.98), 125–500 ms (OR 0.36, 95% CI 0.16–0.82), and >500 ms (OR 0.27, 95% CI 0.11–0.63) were associated with lower probability of VF termination compared to <75 ms interval. DSED interval of >75 ms was associated with lower probability of ROSC compared to <75 ms interval (OR 0.37, 95% CI 0.14–0.98). No association was noted between DSED interval and survival to hospital discharge or neurologic outcome. ConclusionsAmong patients in refractory VF a DSED interval of less than 75 ms was associated with improved rates of VF termination and ROSC. No association was noted between DSED interval and survival to hospital discharge or neurologic outcome.

Out-of-hospital cardiac arrest treated with prehospital double sequential external defibrillation during eCPR in refractory VF — a case report

BackgroundDouble sequential external defibrillation (DSED) has demonstrated increased survival with good neurological outcome in a recent randomized controlled trial. DSED has not been studied in patients with extracorporeal cardiopulmonary resuscitation (eCPR).CaseWe present the first case of prehospital eCPR with ongoing refractory ventricular fibrillation (VF), terminated by DSED. After six shocks, return of spontaneous circulation was initially achieved; however, the patient went into recurrent VF. ECPR was performed prehospital, with VF still refractory after three more shocks. DSED successfully terminated VF and showed a further increase in etCO2 and near-infrared spectroscopy cerebral oximetry values.ConclusionDSED can be a sufficient strategy for patients in refractory VF while on eCPR and should be evaluated in further studies.

Defibrillation strategies for refractory ventricular fibrillation out-of-hospital cardiac arrest: A systematic review and network meta-analysis.

Double sequential external defibrillation (DSED) and vector-change defibrillation (VCD) have been suggested to enhance clinical outcomes for patients with ventricular fibrillation (VF) refractory of standard defibrillation (SD). Therefore, this network meta-analysis aims to evaluate the comparative efficacy of DSED, VCD, and SD for refractory VF. A systematic review and network meta-analysis synthesizing randomized controlled trials (RCTs) and comparative observational studies retrieved from PubMed, EMBASE, WOS, SCOPUS, and Cochrane through November 15th, 2022. R software netmeta and netrank package (R version 4.2.0) and meta-insight software were used to pool dichotomous outcomes using odds ratio (OR) presented with the corresponding confidence interval (CI). Our protocol was prospectively published in PROSPERO with ID: CRD42022378533. We included seven studies with a total of 1632 participants. DSED was similar to SD in survival to hospital discharge (OR: 1.14 with 95% CI [0.55, 2.83]), favorable neurological outcome (modified Rankin scale ≤2 or cerebral performance category ≤2) (OR: 1.35 with 95% CI [0.46, 3.99]), and return of spontaneous circulation (ROSC) (OR: 0.81 with 95% CI [0.43; 1.5]). In addition, VCD was similar to SD in survival to hospital discharge (OR: 1.12 with 95% CI [0.27, 4.57]), favorable neurological outcome (OR: 1.01 with 95% CI [0.18, 5.75]), and ROSC (OR: 0.88 with 95% CI [0.24; 3.15]). Double sequential external defibrillation and VCD were not associated with enhanced outcomes in patients with refractory VF out-of-hospital cardiac arrest, compared to SD. However, the current evidence is still inconclusive, warranting further large-scale RCTs.

PO-05-008 NETWORK META-ANALYSIS OF THE COMPARATIVE EFFICACY OF DOUBLE SEQUENTIAL EXTERNAL, VECTOR-CHANGE, AND STANDARD DEFIBRILLATION FOR REFRACTORY VENTRICULAR FIBRILLATION OUT-OF-HOSPITAL CARDIAC ARREST

Double sequential external defibrillation (DSED; rapid successive shocks from two defibrillators) and vector-change defibrillation (VCD; relocating defibrillation pads anteriorly-posteriorly) have been suggested to enhance clinical outcomes for patients with ventricular fibrillation (VF) refractory of standard defibrillation (SD). This systematic review and network meta-analysis aims to evaluate the comparative efficacy of DSED, VCD, and SD for refractory VF. We conducted a systematic review and network meta-analysis synthesizing randomized controlled trials (RCTs) and comparative observational studies, which were retrieved by systematically searching: PubMed, EMBASE, Web of Science, SCOPUS, and Cochrane through November 15th, 2022. R software netmeta and netrank package (R version 4.2.0) and meta-insight software were used to pool dichotomous outcomes using odds ratio (OR) presented with the corresponding confidence interval (CI). Our protocol was prospectively published in PROSPERO with ID: CRD42022378533. Five retrospective cohorts, one RCT, one pilot RCT, and one case-control study with a total of 1,784 patients were included in our analysis. A total of 439 patients (24.6%) received DSED, 205 patients (11.5%) received VCD, and 1140 patients (n= 63.9%) received SD. In the network meta-analysis, DSED was similar to SD in survival to hospital discharge (OR: 1.14 with 95% CI [0.55, 2.83]), favorable neurological outcome (defined as modified Rankin scale (mRS) or cerebral performance category (CPC) ≤2) (OR: 1.35 with 95% CI [0.46, 3.99]), return of spontaneous circulation (ROSC) (OR: 0.90 with 95% CI [0.53;1.54]), and VF termination (OR: 1.59 with 95% CI [0.92, 2.75]). Also, VCD was similar to SD in survival to hospital discharge (OR: 1.12 with 95% CI [0.27, 4.57]), favorable neurological outcome (OR: 1.01 with 95% CI [0.18, 5.75]), ROSC (OR: 1.06 with 95% CI [0.44, 2.55]), and VF termination (OR: 1.78 with 95% CI [0.95, 3.3]). In the pairwise meta-analysis, there was no difference between DSED and SD in survival to hospital admission (OR: 1.12 with 95% CI [0.58, 2.16]). There was no difference between the use of DSED and VCD compared to SD in patients with out-of-hospital cardiac arrest secondary to refractory VF. However, the current evidence is still not conclusive, warranting further large-scale RCTs.

Defibrillation Strategies for Refractory Ventricular Fibrillation

BackgroundDespite advances in defibrillation technology, shock-refractory ventricular fibrillation remains common during out-of-hospital cardiac arrest. Double sequential external defibrillation (DSED; rapid sequential shocks from two defibrillators) and vector-change (VC) defibrillation (switching defibrillation pads to an anterior–posterior position) have been proposed as defibrillation strategies to improve outcomes in patients with refractory ventricular fibrillation.MethodsWe conducted a cluster-randomized trial with crossover among six Canadian paramedic services to evaluate DSED and VC defibrillation as compared with standard defibrillation in adult patients with refractory ventricular fibrillation during out-of-hospital cardiac arrest. Patients were treated with one of these three techniques according to the strategy that was randomly assigned to the paramedic service. The primary outcome was survival to hospital discharge. Secondary outcomes included termination of ventricular fibrillation, return of spontaneous circulation, and a good neurologic outcome, defined as a modified Rankin scale score of 2 or lower (indicating no symptoms to slight disability) at hospital discharge.ResultsA total of 405 patients were enrolled before the data and safety monitoring board stopped the trial because of the coronavirus disease 2019 pandemic. A total of 136 patients (33.6%) were assigned to receive standard defibrillation, 144 (35.6%) to receive VC defibrillation, and 125 (30.9%) to receive DSED. Survival to hospital discharge was more common in the DSED group than in the standard group (30.4% vs. 13.3%; relative risk, 2.21; 95% confidence interval [CI], 1.33 to 3.67) and more common in the VC group than in the standard group (21.7% vs. 13.3%; relative risk, 1.71; 95% CI, 1.01 to 2.88). DSED but not VC defibrillation was associated with a higher percentage of patients having a good neurologic outcome than standard defibrillation (relative risk, 2.21 [95% CI, 1.26 to 3.88] and 1.48 [95% CI, 0.81 to 2.71], respectively).ConclusionsAmong patients with refractory ventricular fibrillation, survival to hospital discharge occurred more frequently among those who received DSED or VC defibrillation than among those who received standard defibrillation. (Funded by the Heart and Stroke Foundation of Canada; DOSE VF ClinicalTrials.gov number, NCT04080986.)

Latest in Resuscitation Research: Highlights From the 2021 American Heart Association's Resuscitation Science Symposium.

Latest in Resuscitation Research: Highlights From the 2021 American Heart Association's Resuscitation Science Symposium.

A survey of the incidence of defibrillator damage during double sequential external defibrillation for refractory ventricular fibrillation

BackgroundDouble Sequential External Defibrillation (DSED) is a proposed treatment strategy for patients in refractory VF (RVF) during out-of-hospital cardiac arrest (OHCA). Defibrillator damage employing DSED is a theoretical concern expressed by defibrillator manufacturers yet the incidence of damage during resuscitation remains unknown. ObjectiveWe sought to explore the incidence of defibrillator damage employing DSED for RVF during OHCA. MethodsWe conducted a survey of EMS agencies, authors of previous publications, EMS medical directors, base hospital medical oversight groups, and defibrillator manufacturers to assess the incidence of defibrillator damage during DSED. Our survey focused on the frequency of DSED use, number of shocks used during DSED, technique used to employ DSED (simultaneous or sequential), and the incidence of defibrillator damage during DSED. We specifically targeted groups that were known to be using DSED in clinical practice. ResultsOur survey response rate was 50% (65/129): 61% (34/56) EMS medical directors, 60% (6/10) authors, 100% (8/8) base hospitals, 33% (1/3) defibrillator manufacturers, 31% (16/52) paramedic services. In our case-based analysis the overall incidence of defibrillator damage was 0.4%. The incidence of defibrillator damage based on total number of DSED shocks was estimated between 0.11% and 0.22%. All reported cases of defibrillator damage occurred using a simultaneous defibrillation technique. ConclusionWhen DSED is employed using either a sequential or simultaneous technique the rate of defibrillator damage appears to be exceedingly low. Further high-quality evidence is required to determine the impact of DSED on patient centered outcomes, but the incidence of defibrillator damage should not limit it use. Defibrillator damage should continue to be monitored in future trials and clinical practice.

DOuble SEquential External Defibrillation for Refractory Ventricular Fibrillation (DOSE VF): study protocol for a randomized controlled trial

BackgroundDespite high-quality cardiopulmonary resuscitation (CPR), early defibrillation, and antiarrhythmic medications, some patients remain in refractory ventricular fibrillation (VF) during out-of-hospital cardiac arrest. These patients have worse outcomes compared to patients who respond to initial treatment. Double sequential external defibrillation (DSED) and vector change (VC) defibrillation have been proposed as viable options for patients in refractory VF. However, the evidence supporting the use of novel defibrillation strategies is inconclusive. The objective of this study is to compare two novel therapeutic defibrillation strategies (DSED and VC) against standard defibrillation for patients with treatment refractory VF or pulseless ventricular tachycardia (pVT) during out-of-hospital cardiac arrest.Research questionAmong adult (≥ 18 years) patients presenting in refractory VF or pulseless ventricular tachycardia (pVT) during out-of-hospital cardiac arrest, does DSED or VC defibrillation result in greater rates of survival to hospital discharge compared to standard defibrillation?MethodsThis will be a three-arm, cluster randomized trial with repeated crossover conducted in six regions of Ontario, Canada (Peel, Halton, Toronto, Simcoe, London, and Ottawa), over 3 years. All adult (≥ 18 years) patients presenting in refractory VF (defined as patients presenting in VF/pVT and remaining in VF/pVT after three consecutive standard defibrillation attempts during out-of-hospital cardiac arrest of presumed cardiac etiology will be treated by one of three strategies: (1) continued resuscitation using standard defibrillation, (2) resuscitation involving DSED, or (3) resuscitation involving VC (change of defibrillation pads from anterior-lateral to anterior-posterior pad position) defibrillation. The primary outcome will be survival to hospital discharge. Secondary outcomes will include return of spontaneous circulation (ROSC), VF termination after the first interventional shock, VF termination inclusive of all interventional shocks, and number of defibrillation attempts to obtain ROSC. We will also perform an a priori subgroup analysis comparing rates of survival for those who receive “early DSED,” or first DSED shock is shock 4–6, to those who receive “late DSED,” or first DSED shock is shock 7 or later.DiscussionA well-designed randomized controlled trial employing a standardized approach to alternative defibrillation strategies early in the treatment of refractory VF is urgently required to determine if the treatments of DSED or VC defibrillation impact clinical outcomes.Trial registrationClinicalTrials.gov NCT04080986. Registered on 6 September 2019.

Double sequential external defibrillation for refractory ventricular fibrillation: The DOSE VF pilot randomized controlled trial

Double sequential external defibrillation for refractory ventricular fibrillation: The DOSE VF pilot randomized controlled trial

PL02: Double Sequential External Defibrillation for Refractory Ventricular Fibrillation: the DOSE VF pilot randomized controlled trial

Introduction: Despite recent advances in resuscitation, some patients remain in ventricular fibrillation (VF) after multiple defibrillation attempts during out-of-hospital cardiac arrest (OHCA). Vector change defibrillation (VC) and double sequential external defibrillation (DSED) have been proposed as alternate therapeutic strategies for OHCA patients with refractory VF. The primary objective was to determine the feasibility, safety and sample size required for a future cluster randomized controlled trial (RCT) with crossover comparing VC or DSED to standard defibrillation for patients experiencing refractory VF. Secondary objectives were to evaluate the intervention effect on VF termination and return of spontaneous circulation (ROSC). Methods: We conducted a pilot cluster RCT with crossover in four Canadian paramedic services and included all treated adult OHCA patients who presented in VF and received a minimum of three defibrillation attempts. In addition to standard cardiac arrest care, each EMS service was randomly assigned to provide continued standard defibrillation (control), VC or DSED. Services crossed over to an alternate defibrillation strategy after six months. Prior to the launch of the trial, 2,500 paramedics received in-person training for VC and DSED defibrillation using a combination of didactic, video and simulated scenarios. Results: Between March 2018 and September 2019, 152 patients were enrolled. Monthly enrollment varied from 1.4 to 6.1 cases per service. With respect to feasibility, 89.5% of cases received the defibrillation strategy they were randomly allocated to, and 93.1% of cases received a VC or DSED shock prior to the sixth defibrillation attempt. There were no reported cases of defibrillator malfunction, skin burns, difficulty with pad placement or concerns expressed by paramedics, patients, families, or ED staff about the trial. In the standard defibrillation group, 66.6% of cases resulted in VF termination, compared to 82.0% in VC and 76.3% of cases in the DSED group. ROSC was achieved in 25.0%, 39.3% and 40.0% of standard, VC and DSED groups, respectively. Conclusion: Findings from our pilot RCT suggest the DOSE VF protocol is feasible and safe. VF termination and ROSC were higher with VC and DSED compared to standard defibrillation. The results of this pilot trial will allow us to inform a multicenter cluster RCT with crossover to determine if alternate defibrillation strategies for refractory VF may impact patient-centered, clinical outcomes

DOUBLE SEQUENTIAL EXTERNAL DEFIBRILLATION: UNDERUTILIZED IN REFRACTORY ATRIAL FIBRILLATION

Double Sequential External Defibrillation(DSED) is a rarely used but often successful technique utilized in cases of refractory atrial fibrillation when standard direct current cardioversion utilizing a single external defibrillator fails to restore normal sinus rhythm. The technique involves

Successful Resuscitation from Refractory Ventricular Fibrillation by BLS Providers Employing Double Sequential External Defibrillation: A Case Report

Double sequential external defibrillation (DSED) is a novel treatment option for cardiac arrest patients in refractory ventricular fibrillation (VF). There is limited research, however, examining the efficacy of this treatment in clinical practice. Previous research is further confounded by the use of other treatments such as advanced cardiac life support medications. We present the case of the successful use of DSED for refractory out-of-hospital cardiac arrest without the use of advanced life support care.

Double sequential external defibrillation for refractory ventricular fibrillation: The DOSE VF pilot randomized controlled trial

ObjectivesThe primary objective was to determine the feasibility and safety of a cluster randomized controlled trial (RCT) with crossover comparing vector change defibrillation (VC) or double sequential external defibrillation (DSED) to standard defibrillation for patients experiencing refractory ventricular fibrillation (VF). Secondary objectives were to assess the rates of VF termination (VFT) and return of spontaneous circulation (ROSC). MethodsWe conducted a pilot cluster RCT with crossover in four Canadian paramedic services including all treated adult OHCA patients who presented in VF and received a minimum of three successive defibrillation attempts. Each EMS service was randomly assigned to provide standard defibrillation, VC or DSED. Agencies crossed over to an alternate defibrillation strategy after six months. Results152 patients were enrolled. With respect to feasibility, 89.5% of cases received the defibrillation strategy they were randomly allocated to, and 93.1% of cases received a VC or DSED shock prior to the sixth defibrillation attempt. There were no safety concerns reported. In the standard group, 66.6% of cases resulted in VFT, compared to 82.0% in VC and 76.3% in the DSED group. ROSC was achieved in 25.0%, 39.3% and 40.0% of standard, VC and DSED groups, respectively. ConclusionsOur findings suggest the DOSE-VF protocol is feasible and safe. Rates of VFT and ROSC were higher in the VC and DSED than standard defibrillation. The results of this pilot trial will allow us to inform a multicenter cluster RCT with crossover to determine if alternate defibrillation strategies for refractory VF may impact clinical outcomes.

Abstract 149: Double Sequential External Defibrillation in Refractory Ventricular Fibrillation: The Dose VF Pilot Randomized Controlled Trial

Background: Despite significant advances in resuscitation efforts, there are some patients who remain in ventricular fibrillation (VF) after multiple defibrillation attempts during out-of-hospital cardiac arrest (OHCA). Double sequential external defibrillation (DSED) and vector change defibrillation (VC) have been proposed as alternate therapeutic strategies for OHCA patients in shock-refractory VF. Objective: To determine the feasibility, safety and sample size required for a larger, multicentered, 3-arm, cluster randomized controlled trial (RCT) with 2 crossovers comparing DSED or VC to standard defibrillation (control group) for OHCA patients presenting in shock-refractory VF. Methods: We conducted a pilot cluster randomized controlled trial with crossover including all consecutive treated adult OHCA patients who presented in VF and received a minimum of three successive shocks. In addition to standard cardiac arrest care, each EMS agency was randomly assigned to provide standard defibrillation (control), DSED, or VC, followed by crossover to an alternate defibrillation strategy after 6 months. Results: Prior to the launch of the trial, 2,500 paramedics received in-person training in the techniques of DSED and VC defibrillation using a combination of didactic, video and simulated scenarios. Between March 2018 and June 2019, 113 patients were enrolled in 4 Canadian EMS agencies, with zero missed cases. Monthly enrollment varied from 1 to 6 cases per agency. With respect to feasibility, 96% of cases were compliant with the study protocol, and only five (4.4%) cases received a defibrillation strategy that differed from the allocation schedule. There were no reported cases of defibrillator malfunction, no concerns expressed by paramedics, patients, families, or ED staff about the trial, and no reported cases of skin burns or difficulty with pad placement. Conclusions: Findings from our pilot implementation trial suggest the DOSE VF protocol is feasible and safe. The results of this internal pilot trial will allow us to calculate a sample size for a definitive multicenter cluster RCT with crossovers to determine if these alternate defibrillation strategies for OHCA shock refractory VF will impact patient-centered, clinical outcomes.

The impact of double sequential external defibrillation on termination of refractory ventricular fibrillation during out-of-hospital cardiac arrest

BackgroundDespite significant advances in resuscitation efforts, there are some patients who remain in ventricular fibrillation (VF) after multiple shocks during out-of-hospital cardiac arrest (OHCA). Double sequential external defibrillation (DSED) has been proposed as a treatment option for patients in refractory VF. ObjectiveWe sought to explore the relationship between type of defibrillation (standard vs DSED), the number of defibrillation attempts provided and the outcomes of VF termination and return of spontaneous circulation (ROSC) for patients presenting in refractory VF. MethodsWe performed a retrospective review of all treated adult OHCA who presented in VF and received a minimum of three successive standard defibrillations over a three-year period beginning on January 1, 2015 in four Canadian EMS agencies. Using ambulance call reports and defibrillator files, we compared rates of VF termination (defined as the absence of VF at the rhythm check following defibrillation and two minutes of CPR) and VF termination to ROSC for patients who received standard defibrillation and those who received DSED (after on-line medical consultation). Cases with public access defibrillation, those with do not resuscitate orders, and those who presented in VF but terminated VF prior to three shocks were excluded. ResultsOf the 252 patients included, 201 (79.8%) received standard defibrillation only and 51 (20.2%) received at least one DSED. Overall, VF termination was similar between standard defibrillation and DSED (78.1% vs. 76.5%; RR: 1.0; 95% CI: 0.8–1.2). In our shock-based analysis, when early defibrillation attempts were considered (defibrillation attempt 4–8), VF termination was higher for those receiving DSED compared to standard defibrillation (29.4% vs. 17.5%; RR: 1.7; 95% CI: 1.1–2.6). Overall, VF termination to ROSC was similar between standard defibrillation and DSED (21.4% vs. 17.6%; RR: 0.8; 95% CI: 0.4–1.6). Additionally, when early defibrillation attempts were considered (defibrillation attempt 4–8), ROSC was higher for those receiving DSED compared to standard defibrillation (15.7% vs. 5.4%; RR: 2.9; 95% CI: 1.4–5.9). When late defibrillation attempts were considered (defibrillation attempt 9–17), VF termination was higher for those receiving DSED compared to standard defibrillation (31.2% vs. 17.1%; RR: 1.8; 95% CI: 1.1–3.0), but ROSC was rare regardless of defibrillation strategy. When DSED terminated VF into ROSC, it did so with a single DSED attempt in 66.7% of cases. ConclusionsOur observational findings suggest that while overall VF termination and ROSC are similar between standard defibrillation and DSED, earlier DSED may be associated with improved rates of VF termination and ROSC compared to standard defibrillation for refractory VF. A randomized controlled trial is required to assess the impact of early application of DSED on patient-important outcomes.

LO07: Double sequential external defibrillation improves termination of ventricular fibrillation and return of spontaneous circulation in shock-refractory out-of- hospital cardiac arrest

Introduction: Despite significant advances in resuscitation efforts, there are some patients who remain in ventricular fibrillation (VF) after multiple shocks during out-of-hospital cardiac arrest (OHCA). Double sequential external defibrillation (DSED) has been proposed as a treatment option for patients in shock refractory VF. We sought to compare DSED to standard therapy with regards to VF termination and return of spontaneous circulation (ROSC) for patients presenting in shock refractory VF. Methods: We performed a retrospective review of all treated adult OHCA who presented in VF and received a minimum of three successive shocks over a two year period beginning on Jan 1, 2015 in four Canadian EMS agencies. Using ambulance call reports and defibrillator files, we compared VF termination (defined as the absence of VF at the rhythm check following defibrillation and 2 minutes of CPR) and VF termination into a perfusing rhythm with ROSC between patients who received standard therapy (CPR, defibrillation, epinephrine and antiarrhythmics) and those who received DSED (after on-line medical consultation) for shock refractory VF. Cases of traumatic cardiac arrest and those who presented in VF but terminated VF prior to 3 successive shocks were excluded. Results: Among 197 patients who met the study criteria for shock refractory VF, 161 (81.7%) patients received standard therapy and 36 (18.3%) received DSED. For the primary outcome, VF termination was significantly higher for DSED compared to standard therapy (63.9% vs 18.0%; Δ45.9%; 95% CI: 28.3 to 60.5). For the secondary outcome of VF termination into ROSC, DSED was associated with significantly higher ROSC compared to standard care (33.3% vs 13%; Δ20.3%; 95% CI:13.0 to 33.3). The median (IQR) number of failed standard shocks prior to DSED was 8 (6, 10). When DSED terminated VF, it did so with a single DSED shock in 69.6% of cases. Conclusion: Our observational findings suggest improved VF termination and ROSC are associated with DSED compared to standard therapy for shock refractory VF. An appropriately powered randomized controlled trial is required to assess the impact of DSED on patient-important outcomes.

P029: A descriptive analysis of defibrillation vector change for prehospital refractory ventricular fibrillation

Introduction: Patients in ventricular fibrillation (VF) who do not respond to standard Advanced Cardiac Life Support treatments are deemed to be in refractory VF (rVF). The ideal prehospital treatment for patients with rVF remains unknown. Double sequential external defibrillation (DSED) has been proposed as a viable option for patients in rVF. Although the mechanism by which DSED terminates rVF remains unknown, one theory is that the change in defibrillation vector that occurs may contribute. The objective of this study was to describe clinical outcomes for patients presenting in rVF during out-of-hospital cardiac arrest (OOHCA) for those who underwent vector change defibrillation, compared to those who received standard treatment. Methods: This was a retrospective chart review of adult (18 years) patients presenting in rVF during OOHCA over 15 months beginning in March 2016. Patients who underwent vector change defibrillation had a change in pad position (anterior-anterior to anterior-posterior) after 3 or more consecutive shocks. Termination of rVF was defined as the absence of VF after a vector change or standard shock during the next rhythm analysis. Results: There were 372 OOHCA, with 25 (6.7%) patients meeting our definition of rVF. Of these, 16 (64.0%) patients (median age 62 years, 81.3% male) had vector change after a median (IQR) of 3 (3.0-4.0) paramedic defibrillation attempts. Median (IQR) time to vector change defibrillation was 8.8 (7.1-11.1) minutes. Eight (50%) patients had termination of rVF after the first vector change shock, 6 (37.5%) had prehospital return of spontaneous circulation (ROSC) and 5 (31.3%) patients survived to hospital discharge. Of the 9 rVF patients who did not have vector change, median age was 63 years and 88.9% were male. The median (IQR) number of defibrillations within this group was 5 (4.5-7.0). No patients converted after the 4th defibrillation. Prehospital ROSC was achieved in 3 (33.3%) patients and 5 (55.5%) patients were transported while in rVF . Three patients (33.3%) survived to hospital discharge. Conclusion: This is preliminary evidence that vector change defibrillation in patients with rVF may result in VF termination. A randomized controlled trial is warranted to test whether or not vector change has a role in the termination of rVF.