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Background: We explored the feasibility of a large-scale UK ambulance services trial of optimal defibrillation shock energy for out-of-hospital cardiac arrest. The primary objective of this feasibility study was to establish the number of eligible patients and the number recruited. Secondary outcomes were adherence to allocated treatment and data completeness. Methods: We conducted a three-arm parallel group cluster randomised controlled feasibility study in a single ambulance service in southern England. Adult patients in out-of-hospital cardiac arrest treated for a shockable rhythm were included. Zoll X series defibrillators (clusters) were randomised to deliver 120–150–200 J, 150–200–200 J, or 200–200–200 J shock strategies. Results: Between March 2022 and February 2023, we randomised 38 eligible patients (120–150–200 J (n = 12), 150–200–200 J (n = 10), 200–200–200 J (n = 16)) to the study. The recruitment rate per cluster was 0.07 per month. The median patient age was 71 years (IQR 59–81 years); 79% were male. Twenty-eight cardiac arrests (74%) occurred in a private residence, 29 (76%) were witnessed and 32 (84%) patients received bystander CPR. Treatment adherence was 93% and completeness of clinical and electrical outcomes was 86%. At 30 days, 3/36 (8.3%) patients survived; we were unable to collect survival outcomes for two patients. Defibrillation data collection became difficult when defibrillators became separated from their allocated vehicles. Conclusion: We have demonstrated the feasibility of a cluster randomised controlled trial of optimal shock energy for defibrillation in a UK ambulance service. We have identified possible solutions to issues relating to trial design.

Aims: The PARAMEDIC-3 trial evaluates the clinical and cost-effectiveness of an intraosseous first strategy, compared with an intravenous first strategy, for drug administration in adults who have sustained an out-of-hospital cardiac arrest. Methods: PARAMEDIC-3 is a pragmatic, allocation concealed, open-label, multi-centre, superiority randomised controlled trial. It will recruit 15,000 patients across English and Welsh ambulance services. Adults who have sustained an out-of-hospital cardiac arrest are individually randomised to an intraosseous access first strategy or intravenous access first strategy in a 1:1 ratio through an opaque, sealed envelope system. The randomised allocation determines the route used for the first two attempts at vascular access. Participants are initially enrolled under a deferred consent model.The primary clinical-effectiveness outcome is survival at 30-days. Secondary outcomes include return of spontaneous circulation, neurological functional outcome, and health-related quality of life. Participants are followed-up to six-months following cardiac arrest. The primary health economic outcome is incremental cost per quality-adjusted life year gained. Conclusion: The PARAMEDIC-3 trial will provide key information on the clinical and cost-effectiveness of drug route in out-of-hospital cardiac arrest.Trial registration: ISRCTN14223494, registered 16/08/2021, prospectively registered.

Aim: To determine the optimal first-shock energy level for biphasic defibrillation and whether fixed or escalating protocols for subsequent shocks are most effective. Methods: We searched Medline, Embase, Cochrane CENTRAL, CINAHL, the Web of Science and national and international trial registry databases for papers published from database inception to January 2022. We reviewed reference lists of key papers to identify additional references. The population included adults sustaining non traumatic out-of-hospital cardiac arrest subject to attempted defibrillation. Studies of internal or monophasic defibrillation and studies other than randomised controlled trials or prospective cohorts were excluded. Two reviewers assessed study relevance. Data extraction and risk of bias assessment, using the ROBINS-I tool, were conducted by one reviewer and checked by a second reviewer. Data underwent intention-to-treat analysis. Results: We identified no studies evaluating first shock energy. Only one study (n = 738) comparing fixed versus escalating energy met eligibility criteria: a prospective cohort analysis of a randomised controlled trial of manual versus mechanical CPR. High fixed (360 J) energy was compared with an escalating (200–200/300–360 J) strategy. Researchers found 27.5% (70/255) of patients in the escalating energy group and 27.61% (132/478) in the fixed high energy group survived to hospital discharge (unadjusted risk ratio 0.99, 95% CI 0.73, 1.23). Results were of very low certainty as the study was at serious risk of bias. Conclusion: This systematic review did not identify an optimal first-shock energy for biphasic defibrillation. We identified no survival advantage at 30 days when comparing 360 J fixed with 200 J escalating strategy.

Background: Mechanical chest compression devices may help to maintain high-quality cardiopulmonary resuscitation (CPR), but little evidence exists for their effectiveness. We evaluated whether or not the introduction of Lund University Cardiopulmonary Assistance System-2 (LUCAS-2; Jolife AB, Lund, Sweden) mechanical CPR into front-line emergency response vehicles would improve survival from out-of-hospital cardiac arrest (OHCA). Objective: Evaluation of the LUCAS-2 device as a routine ambulance service treatment for OHCA. Design: Pragmatic, cluster randomised trial including adults with non-traumatic OHCA. Ambulance dispatch staff and those collecting the primary outcome were blind to treatment allocation. Blinding of the ambulance staff who delivered the interventions and reported initial response to treatment was not possible. We also conducted a health economic evaluation and a systematic review of all trials of out-of-hospital mechanical chest compression. Setting: Four UK ambulance services (West Midlands, North East England, Wales and South Central), comprising 91 urban and semiurban ambulance stations. Clusters were ambulance service vehicles, which were randomly assigned (approximately 1 : 2) to the LUCAS-2 device or manual CPR. Participants: Patients were included if they were in cardiac arrest in the out-of-hospital environment. Exclusions were patients with cardiac arrest as a result of trauma, with known or clinically apparent pregnancy, or aged