Defibrillation Strategies for Refractory Ventricular Fibrillation.

BACKGROUND: Despite 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. METHODS: We 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. RESULTS: A 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). CONCLUSIONS: Among 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.).

A Quality Improvement Initiative to Increase Confirmation of Prehospital Endotracheal Tube Placement at Emergency Department Transfer of Care.

OBJECTIVES: Rates of prehospital unplanned extubation (UE) range from 0 to 25% and are the result of many factors, including patient movement. Transfer of care of intubated patients to the emergency department (ED) involves significant patient movement and represents a high-risk event for UE. Frequent confirmation of endotracheal tube (ETT) placement is imperative for early recognition of UE and to minimize patient harm. METHODS: Local Practice-Our baseline rate of verbal ETT position confirmation with a member of the ED team during ED transfer of care was 74%. Our goal was to increase this practice to >90% in six months. This project was completed in partnership with Toronto Paramedic Services. Prehospital electronic patient care records (ePCRs) were reviewed weekly to determine the proportion of intubated patients who had ETT placement confirmed in the ED at transfer of care. Interventions-Pre- and post-project paramedic focus groups were conducted to identify potential drivers, change ideas, and project feedback. Three staggered interventions were introduced over five months: (1) memorandums to paramedics, ED chiefs and respiratory therapy leads, (2) individualized paramedic feedback e-mails, and (3) ePCR changes and closing rules. RESULTS: The pre-project focus group identified several potential drivers, such as physical barriers, interprofessional relationships, and communication. ETT confirmation remained ≥90% for the last eight weeks and interventions resulted in special cause variation. Median cases without verbal confirmation between paramedics and ED staff reduced from 5/week (IQR 2.5, 6.5) to 1/week (IQR 0, 2). UE was identified in 0.6% (2/340) of patients with ETT confirmation. The post-project focus group noted improvements in perceived accountability, interprofessional relationships, and satisfaction with interventions. CONCLUSION: Through a series of interventions, we improved the rate of ETT confirmation during ED transfer of care. Although rates of UE were low, improvement in ETT confirmation may lead to faster recognition of UE when it does occur thereby mitigating complications. The observed improvement was sustained after interventions ended.

Safety and Adverse Events During Primary Care Paramedic Interfacility Transfer of Stable STEMI Patients.

OBJECTIVE: Current guidelines recommend that patients presenting with ST-elevation myocardial infarction (STEMI) to hospitals not capable of performing primary percutaneous coronary intervention (PCI) be transferred to a PCI-capable hospital if reperfusion can be accomplished within 120 min. Most STEMI patients are accompanied by an advanced care paramedic (ACP, equivalent to EMT-P), nurse, or physician who can manage complications should they arise. In our region, stable STEMI patients are transported by primary care paramedics (PCPs, similar scope of practice to advanced EMT) in cases where a nurse, physician, or ACP paramedic is not available. Our goal was to describe adverse events and need for advanced interventions among initially stable STEMI patients during interfacility transfer by PCPs. METHODS: We reviewed ambulance and hospital records of initially stable STEMI patients (as determined by first set of vital signs documented by paramedics) transferred to a PCI-capable hospital by PCPs between March 1, 2014, and December 31, 2019. We identified whether pre-determined adverse clinical events occurred during the transport as well as the potential need for advanced care interventions not within the PCP scope of practice. Adverse events upon arrival in the PCI lab were also identified. RESULTS: Of 346 STEMI patients transferred, 179 met inclusion criteria. The mean age of included patients was 61 years (SD 12.1) and 74.9% (134/179) were male. Median transport interval was 36 min (IQR 3.0). During transport, 47/179 (26.0%) patients experienced pre-defined adverse events; for 16/47 (34%), one or more adverse events was major. Three patients met criteria for ACP interventions. One patient suffered a cardiac arrest and was promptly resuscitated with defibrillation by the PCPs. CONCLUSIONS: We found PCP-interfacility transport of initially stable STEMI patients was safe and associated with a moderate proportion of adverse events, the majority of which did not require an advanced care intervention. These findings may help decision-making to avoid delays transferring stable patients to PCI-capable centers.

Call 911: Lower Ambulance Utilization Among Young Adults, Especially Women, with Stroke.

BACKGROUND: Delayed presentation to the emergency department influences acute stroke care and can result in worse outcomes. Despite public health messaging, many young adults consider stroke as a disease of older people. We determined the differences in ambulance utilization and delays to hospital presentation between women and men as well as younger (18-44 years) versus older (≥45 years) patients with stroke. METHODS: We conducted a population-based retrospective study using national administrative health data from the Canadian Institute of Health Information databases and examined data between 2003 and 2016 to compare ambulance utilization and time to hospital presentation across sex and age. RESULTS: Young adults account for 3.9% of 463,310 stroke/transient ischemic attack/hemorrhage admissions. They have a higher proportion of hemorrhage (37% vs. 15%) and fewer ischemic events (50% vs. 68%) compared with older patients. Younger patients are less likely to arrive by ambulance (62% vs. 66%, p < 0.001), with younger women least likely to use ambulance services (61%) and older women most likely (68%). Median stroke onset to hospital arrival times were 7 h for older patients and younger men, but 9 h in younger women. There has been no improvement among young women in ambulance utilization since 2003, whereas ambulance use increased in all other groups. CONCLUSIONS: Younger adults, especially younger women, are less likely to use ambulance services, take longer to get to hospital, and have not improved in utilization of emergency services for stroke over 13 years. Targeted public health messaging is required to ensure younger adults seek emergency stroke care.

Catecholaminergic Polymorphic Ventricular Tachycardia: An Unusual Case of Fright-Induced Prehospital Cardiac Arrest in a Healthy 6-Year-Old Child.

Catecholaminergic Polymorphic Ventricular Tachycardia is a rare but often lethal genetic disorder that affects approximately 1 in 10,000 people. It often first manifests as stress or exercise-related syncope or sudden unexplained cardiac death, primarily in the pediatric and young adult population. We present a case of a 6-year-old male who had a sudden unexplained prehospital cardiac arrest after being scared by a domestic animal and who presented in ventricular fibrillation. The patient was subsequently defibrillated with a return of spontaneous circulation. During the course of care, medications with beta-1 and -2 agonist properties were administered, followed by multiple further episodes of polymorphic ventricular tachycardia (PVT)/ventricular fibrillation (VF). Once these medications were discontinued and beta blockers were administered, the patient had no further episodes of PVT/VF and was subsequently discharged from hospital 7 days later, completely neurologically intact. This case suggests the need for caution when considering administering beta agonists in a pediatric cardiac arrest patient with no known history of heart disease who presents in VF or PVT after an incident of extreme stress or strenuous physical activity.

CPR Induced Consciousness During Out-of-Hospital Cardiac Arrest: A Case Report on an Emerging Phenomenon.

BACKGROUND: High quality cardiopulmonary resuscitation (CPR) has produced a relatively new phenomenon of consciousness in patients with vital signs absent. Further research is necessary to produce a viable treatment strategy during and post resuscitation. OBJECTIVE: To provide a case study done by paramedics in the field illustrating the need for sedation in a patient whose presentation was consistent with CPR induced consciousness. Resuscitative challenges are provided as well as potential future treatment options to minimize harm to both patients and prehospital providers. CASE REPORT: A 52-year-old male presented as a witnessed out-of-hospital cardiac arrest (OHCA). During CPR the patient began to exhibit signs of life including severe agitation and thrashing of his limbs while CPR was ongoing for ventricular fibrillation prior to defibrillation. Resuscitation became considerably more complicated due to the violent and counterintuitive motions done by the patient during their own resuscitation. Despite the atypical presentation of cardiac arrest the patient was successfully resuscitated employing high quality CPR, standard advanced life support (ALS) care as well as two double sequential external defibrillation shocks. The patient underwent emergency percutaneous coronary intervention (PCI) for a 100% occlusion of his left anterior descending artery (LAD). The patient returned home 3 days later fully recovered with a Cerebral Performance Score of 1. CONCLUSION: CPR induced consciousness is emerging as a new phenomenon challenging providers of high quality CPR during cardiac arrest resuscitation. Our case report describes the manifestations of CPR induced consciousness as well as the resuscitative challenges which occur during resuscitation. Further research is required to determine the true frequency of this condition as well as treatment algorithms that would allow for appropriate and safe management for both the patient and EMS providers.

Factors associated with out-of-hospital cardiac arrest with pulseless electric activity: A population-based study.

BACKGROUND: Many patients with out-of-hospital cardiac arrest present with pulseless electric activity (PEA) rather than shockable rhythm. Despite improvements in resuscitation care, survival of PEA patients remains dismal. Our main objective was to characterize out-of-hospital cardiac arrest patients by initial presenting rhythm and to evaluate independent determinants of PEA. METHODS: A population-based study was conducted using the Toronto Rescu Epistry database with linkage to administrative data in Ontario, Canada. We included patients older than 20 years who had nontraumatic cardiac arrests from 2005 to 2010. Multivariable logistic regression models were constructed to determine factors predicting the occurrence of PEA vs shockable rhythm vs asystole. RESULTS: Of the 9,882 included patients who received treatment, 24.5% had PEA, 26.3% had shockable rhythm, and 49.2% had asystole. Patients with PEA had a mean age of 72 years, 41.2% were female and had multiple comorbidities, and 53.4% were hospitalized in the past year. As compared with shockable rhythm, PEA patients were older, were more likely to be women, and had more comorbidities. As compared with asystole, PEA patients had similar baseline and clinical characteristics, but were substantially more likely to have an arrest witnessed by emergency medical services (odds ratio 13) or by bystander (odds ratio 3.24). Mortality at 30 days was 95.5%, 77.9%, and 98.9% for patients with PEA, shockable rhythm, asystole, respectively. CONCLUSIONS: Patient characteristics differed substantially in those presenting with PEA and shockable rhythm. In contrast, the main distinguishing factor between PEA and asystole cardiac arrest related mainly to factors at the time of the cardiac arrest.

Double Sequential External Defibrillation and Survival from Out-of-Hospital Cardiac Arrest: A Case Report.

BACKGROUND: Patients who present in ventricular fibrillation are typically treated with cardiopulmonary resuscitation (CPR), epinephrine, antiarrhythmic medications, and defibrillation. Although these therapies have shown to be effective, some patients remain in a shockable rhythm. Double sequential external defibrillation has been described as a viable option for patients in refractory ventricular fibrillation. OBJECTIVE: To describe the innovative use of two defibrillators used to deliver double sequential external defibrillation by paramedics in a case of refractory ventricular fibrillation resulting in prehospital return of spontaneous circulation and survival to hospital discharge with good neurologic function. CASE: A 28-year-old female sustained a witnessed out-of-hospital cardiac arrest (OHCA). Bystander CPR was performed by her husband followed by paramedics providing high-quality CPR, antiarrhythmic medication, and 6 biphasic defibrillations using standard energy levels. Double sequential external defibrillation was applied and a return of spontaneous circulation was attained on scene and maintained through to arrival to the emergency department. Following admission to hospital the patient was diagnosed with long QT syndrome. An implantable cardioverter defibrillator was placed and the patient was discharged with a Cerebral Performance Category of 2 as well as a modified Rankin Scale of 2 after an 18-day hospital stay. The patient's functional status continued to improve post discharge. CONCLUSION: The addition of double sequential external defibrillation as part of a well-organized resuscitation effort may be a valid treatment option for OHCA patients who present in refractory ventricular fibrillation.

A Novel Approach to Improve Time to First Shock in Prehospital STEMI Complicated by Ventricular Fibrillation.

Lethal cardiac arrhythmias such as ventricular fibrillation and pulseless ventricular tachycardia (VF/pVT) complicate up to 6% of all out-of-hospital STEMIs. Typically, paramedics respond to this by applying defibrillation pads and delivering a shock as soon as possible. A recently introduced "pads-on" protocol directed paramedics to apply defibrillation pads to all STEMI patients (regardless of clinical stability) with the aim of decreasing time to first shock. In this article we present two cases of prehospital STEMI complicated by VF to illustrate times to first shock for the two different protocols. One case each of a STEMI complicated by VF before implementation of the pads-on protocol and after the implementation of the protocol is presented. An important difference in the time to first shock is noted between the two patients with STEMI complicated by VF. While it took 2 min 43 s for the pads-off patient to be defibrillated, only 27 s elapsed before the pads-on patient was defibrillated. These two cases demonstrate that the application of defibrillation pads immediately following the diagnosis of prehospital STEMI has the potential to decrease the time to shock in patients suffering VF/pVT.

Trends in short- and long-term survival among out-of-hospital cardiac arrest patients alive at hospital arrival.

BACKGROUND: Out-of-hospital cardiac arrest (OHCA) is associated with a poor prognosis and poses a significant burden to the healthcare system, but few studies have evaluated whether OHCA incidence and survival have changed over time. METHODS AND RESULTS: A population-based cohort study was conducted, including 34 291 OHCA patients >20 years of age who were transported alive to the emergency department of an acute-care hospital from April 1, 2002, to March 31, 2012, in Ontario, Canada. Patients with life-threatening trauma and those who died before hospital arrival were excluded. The overall age- and sex-standardized incidence of OHCA patients who were transported alive was 36 cases per 100 000 persons and did not significantly change over the study period. Cardiac risk factor prevalence increased significantly, whereas the rate of most cardiovascular conditions decreased significantly. The 30-day survival improved from 9.4% in 2002 to 13.6% in 2011; 1-year survival improved from 7.7% to 11.8% (P<0.001). Patients hospitalized in 2011 were significantly more likely to survive 30 days (adjusted odds ratio, 1.47 [95% CI, 1.22-1.77]) and 1 year (adjusted odds ratio, 1.55 [95% CI, 1.27-1.91]) compared with 2002. A significant interaction between temporal trends in survival improvement and age group was observed in which the improvement in survival was largest in the youngest age groups. CONCLUSIONS: OHCA patients who were transported alive are increasingly likely to have cardiovascular risk factors but less likely to have previous cardiovascular conditions. The overall incidence of OHCA patients transported to hospital alive did not change over the past decade. Short- and longer-term survival after OHCA has substantially improved, with younger patients experiencing the greatest improvement.

Assessment of the safety and effectiveness of emergency department STEMI bypass by defibrillation-only emergency medical technicians/primary care paramedics.

INTRODUCTION: The American Heart Association (AHA) suggests emergency medical service (EMS) providers transporting ST-segment elevation myocardial infarction (STEMI) patients to a percutaneous coronary intervention (PCI) center require advanced life support (ALS) skills. OBJECTIVES: To evaluate the potential safety and time savings effectiveness of defibrillation-only emergency medical technician/primary care paramedic (EMT-D/PCP) EMS transport to a PCI center in a system where only emergency medical technician-paramedics/advanced care paramedics (EMT-Ps/ACPs) are authorized to bypass non-PCI hospitals. METHODS: We reviewed 89 consecutive patients meeting STEMI criteria transported by EMT-Ds/PCPs per protocol by one of three paths: 1) closest non-PCI center emergency department (ED) with secondary transfer by EMT-Ps/ACPs to a PCI lab, 2) rendezvous with EMT-Ps/ACPs and diversion to a PCI lab, and 3) PCI center ED if it was closest. Actual transport times to the PCI center ED were compared to predicted transport times determined by mapping software had EMT-Ds/PCPs followed a direct path. Lastly, we recorded predefined clinically important events and advanced care interventions. RESULTS: Twenty-seven, 51, and 11 patients followed paths 1, 2, and 3 respectively. Median transport times for path 1 were 6 (IQR 5) minutes to reach the nearest non-PCI center ED and 66 (IQR 45) minutes to the PCI center ED compared to a median predicted 13 (IQR 7) minutes to a PCI center ED had EMT-Ds/PCPs followed a direct path. Median transport time for path 2 was 12 (IQR 8) minutes compared to a median predicted time of 11 (IQR 6) minutes had no EMT-P/ACP rendezvous occurred. Median transport time for path 3 was 7 minutes (IQR 5). Three patients experienced prehospital cardiac arrest; 1 required dopamine, and 4 others received a saline bolus for hypotension. CONCLUSIONS: Substantial time savings may occur if EMT-Ds/PCPs bypass non-PCI center EDs with only a small predicted increase (about 7 minutes) in the transport time to the PCI center ED. EMT-P/ACP rendezvous does not appear to substantially increase transport time. Given the relatively low occurrence of clinically important events, our findings suggest that EMT-D/PCP bypass to a PCI center ED may be safe and effective for selected STEMI patients.

Clinical events and treatment in prehospital patients with ST-segment elevation myocardial infarction.

BACKGROUND: Little is known about clinically important events and advanced care treatment that patients with ST-segment elevation myocardial infarction (STEMI) encounter in the prehospital setting. OBJECTIVES: We sought to determine the proportion of community patients with STEMI who experienced a clinically important event or received advanced care treatment prior to arrival at a designated percutaneous coronary intervention (PCI) laboratory or emergency department (ED). METHODS: We reviewed 487 consecutive community patients with STEMI between May 2008 and June 2009. All patients were geographically within a single large "third-service" urban emergency medical services (EMS) system and were transported by paramedics with an advanced care scope of practice. We recorded predefined clinically important events and advanced care treatment that occurred in patients being transported directly to a PCI laboratory or ED (group 1) or interfacility transfer to a PCI laboratory (group 2). RESULTS: One or more clinically important events occurred in 92 of 342 (26.9%) group 1 patients and nine of 145 (6.2%) group 2 patients. The most common were sinus bradycardia, hypotension, and cardiac arrest. Additionally, 33 of 342 (9.6%) group 1 and nine of 145 (6.2%) group 2 patients received one or more advanced care treatments. The most common were administration of morphine and administration of atropine. Eight group 1 patients and three group 2 patients received cardiopulmonary resuscitation (CPR) or defibrillation. CONCLUSIONS: Clinically important events and advanced care treatment are common in community STEMI patients undergoing prehospital transport or interfacility transfer to a PCI center. Several patients required CPR or defibrillation. Further research is needed to define the clinical experience of STEMI patients during the out-of-hospital phase and the scope of practice required of EMS providers to safely manage these patients.

Serial prehospital 12-lead electrocardiograms increase identification of ST-segment elevation myocardial infarction.

BACKGROUND: Many prehospital protocols require acquisition of a single 12-lead electrocardiogram (ECG) when assessing a patient for ST-segment elevation myocardial infarction (STEMI). However, it is known that ECG evidence of STEMI can evolve over time. OBJECTIVES: To determine how often the first and, if necessary, second or third prehospital ECGs identified STEMI, and the time intervals associated with acquiring these ECGs and arrival at the emergency department (ED). METHODS: We retrospectively analyzed 325 consecutive prehospital STEMIs identified between June 2008 and May 2009 in a large third-service emergency medical services (EMS) system. If the first ECG did not identify STEMI, protocol required a second ECG just before transport and, if necessary, a third ECG before entering the receiving ED. Paramedics who identified STEMI at any time bypassed participating local EDs, taking patients directly to the percutaneous coronary intervention (PCI) center. Paramedics used computerized ECG interpretation with STEMI diagnosis defined as an "acute MI" report by GE/Marquette 12-SL software in ZOLL E-series defibrillator/cardiac monitors (ZOLL Medical, Chelmsford, MA). We recorded the time of each ECG, and the ordinal number of the diagnostic ECG. We then determined the number of cases and frequency of STEMI diagnosis on the first, second, or third ECG. We also measured the interval between ECGs and the interval from the initial positive ECG to arrival at the ED. Results. STEMI was identified on the first prehospital ECG in 275 cases, on the second ECG in 30 cases, and on the third ECG in 20 cases (cumulative percentages of 84.6%, 93.8%, and 100%, respectively). For STEMIs identified on the second or third ECG, 90% were identified within 25 minutes after the first ECG. The median times from identification of STEMI to arrival at the ED were 17.5 minutes, 11.0 minutes, and 0.7 minutes for STEMIs identified on the first, second, and third ECGs, respectively. CONCLUSIONS: A single prehospital ECG would have identified only 84.6% of STEMI patients. This suggests caution using a single prehospital ECG to rule out STEMI. Three serial ECGs acquired over 25 minutes is feasible and may be valuable in maximizing prehospital diagnostic yield, particularly where emergent access to PCI exists.

Evidence-based optimization of urban firefighter first response to emergency medical services 9-1-1 incidents.

INTRODUCTION: Many emergency medical services (EMS) systems dispatch nonparamedic firefighter first responders (FFRs) to selected EMS 9-1-1 calls, intending to deliver time-sensitive interventions such as defibrillation, cardiopulmonary resuscitation (CPR), and bag-mask ventilation prior to arrival of paramedics. Deciding when to send FFRs is complicated because critical cases are rare, paramedics often arrive before FFRs, and lights-and-siren responses by emergency vehicles are associated with the risk of en-route traffic collisions. OBJECTIVE: To describe a methodology allowing EMS systems to optimize their own FFR programs using local data, and reflecting local medical oversight policy and local risk-benefit opinion. METHODS: We constructed a generalized input-output model that retrospectively reviews EMS dispatch and electronic prehospital clinical records to identify a subset of Medical Priority Dispatch System (MPDS) call categories ("determinants") that maximize the opportunities for FFR interventions while minimizing unwarranted responses. Input parameters include local FFR interventions, the local FFR "first-on-scene" rate, and the locally acceptable ratio of risk to benefit. The model uses a receiver-operating characteristic (ROC) curve to identify the optimal mix of response specificity and sensitivity achieved by sending FFRs to progressively more categories of EMS calls while remaining within a defined risk-benefit ratio. The model was applied to a 16-month retrospective sample of 220,358 incidents from a large urban EMS system to compare the model's recommendations with the system's current practices. RESULTS: The model predicts that FFR lights-and-siren responses in the sample could be reduced by 83%, from 93,058 to 16,091 incidents, by confining FFR responses to 27 of 509 MPDS dispatch determinants, representing 7.3% of incidents but 58.9% of all predicted FFR interventions. Of the 93,058 incidents, another 58,275 incidents could be downgraded to safer nonemergency FFR responses and 18,692 responses could be eliminated entirely, improving the specificity of FFR response from 57.8% to 93.0%. CONCLUSIONS: This model provides a robust generalized methodology allowing EMS systems to optimize FFR lights-and-siren responses to emergency medical calls. Further validation is warranted to assess the model's generality.

Clinical considerations for out-of-hospital cardiac arrest management during COVID-19.

Managing out-of-hospital cardiac arrest requires paramedics to perform multiple aerosol generating medical procedures in an uncontrolled setting. This increases the risk of cross infection during the COVID-19 pandemic. Modifications to conventional protocols are required to balance paramedic safety with optimal patient care and potential stresses on the capacity of critical care resources. Despite this, little specific advice has been published to guide paramedic practice. In this commentary, we highlight challenges and controversies regarding critical decision making around initiation of resuscitation, airway management, mechanical chest compression, and termination of resuscitation. We also discuss suggested triggers for implementation and revocation of recommended protocol changes and present an accompanying paramedic-specific algorithm.

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

BACKGROUND: Despite 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 QUESTION: Among 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? METHODS: This 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. DISCUSSION: A 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 REGISTRATION: ClinicalTrials.gov NCT04080986 . Registered on 6 September 2019.

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

OBJECTIVES: The 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). METHODS: We 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. RESULTS: 152 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. CONCLUSIONS: Our 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.

Validation of a rule for termination of resuscitation in out-of-hospital cardiac arrest.

BACKGROUND: We prospectively evaluated a clinical prediction rule to be used by emergency medical technicians (EMTs) trained in the use of an automated external defibrillator for the termination of basic life support resuscitative efforts during out-of-hospital cardiac arrest. The rule recommends termination when there is no return of spontaneous circulation, no shocks are administered, and the arrest is not witnessed by emergency medical-services personnel. Otherwise, the rule recommends transportation to the hospital, in accordance with routine practice. METHODS: The study included 24 emergency medical systems in Ontario, Canada. All patients 18 years of age or older who had an arrest of presumed cardiac cause and who were treated by EMTs trained in the use of an automated external defibrillator were included. The patients were treated according to standard guidelines. Characteristics of diagnostic tests for the prediction rule were calculated. These characteristics include sensitivity, specificity, and positive and negative predictive values. RESULTS: Follow-up data were obtained for all 1240 patients. Of 776 patients with cardiac arrest for whom the rule recommended termination, 4 survived (0.5 percent). The rule had a specificity of 90.2 percent for recommending transport of survivors to the emergency department and had a positive predictive value for death of 99.5 percent when termination was recommended. Implementation of this rule would result in a decrease in the rate of transportation from 100 percent of patients to 37.4 percent. The addition of other criteria (a response interval greater than eight minutes or a cardiac arrest not witnessed by a bystander) would further improve both the specificity and positive predictive value of the rule but would result in the transportation of a larger proportion of patients. CONCLUSIONS: The use of a clinical prediction rule for the termination of resuscitation may help clinicians decide whether to terminate basic life support resuscitative efforts in patients having an out-of-hospital cardiac arrest.

Validation of a universal prehospital termination of resuscitation clinical prediction rule for advanced and basic life support providers.

BACKGROUND: Prehospital termination of resuscitation rules have been derived for Emergency Medical Technician-Paramedics providing advanced life support care and defibrillation-only Emergency Medical Technicians providing basic life support care. We sought to externally validate each rule on a prospective cohort of prehospital cardiac arrest patients to determine if either rule could be proposed as a universal prehospital termination of resuscitation rule. METHODS: Investigators at the University of Toronto performed a secondary cohort analysis of data prospectively collected for the Resuscitation Outcomes Consortium Epistry-Cardiac Arrest trial from 1 April 2006 to 1 April 2007 by one site. The diagnostic test characteristics and predicted transportation rate were calculated for each rule. RESULTS: Of the 2415 patients with cardiac arrest of presumed cardiac etiology, the advanced life support rule recommended termination of resuscitation for 743 patients. No survivors were identified in this group. It had a specificity of 100% for recommending transport of potential survivors, a positive predictive value of 100% for death and a predicted transport rate of 69%. The basic life support rule recommended termination of resuscitation for 1302 patients, with no survivors. This rule had a specificity of 100%, a positive predictive value of 100% and a predicted transport rate of 46%. CONCLUSIONS: Implementing the basic life support rule as a universal termination of resuscitation clinical prediction rule would result in a lower overall transport rate without missing any potential survivors. The universal rule would recommend termination of resuscitation when there was no return of spontaneous circulation prior to transport, no shock was given and the arrest was not witnessed by Emergency Medical Services personnel. This rule may be useful for emergency medical services systems with mixed levels of providers responding to cardiac arrest patients.