Award Title: A feasibility study for a randomised trial to assess prehospital optimal shock energy for defibrillation in cardiac arrest
Funder: Health Education England

Abstract: BackgroundThe International Liaison Committee on Resuscitation (ILCOR) has identified defibrillation energy levels as a priority area for research (Soar et al, 2015a). In the absence of definitive evidence, UK Ambulance Services employ a range of initial shock energies and differing strategies for subsequent shocks (fixed versus escalating energy). The optimal strategy remains unknown and there is concern that insufficient energy may fail to cardiovert and excess energy may risk myocardial damage (manifest by conversion to a non-perfusing rhythm, refibrillation, or myocardial stunning). Defibrillatory shocks and provision of quality CPR remain the only interventions proven to positively impact outcome. Detailed guidance on characteristics of optimal CPR is now available (Soar et al, 2015b) whereas the evidence base for defibrillation shock energy is still lacking. In 2010, ILCOR guidance changed from three stacked shocks (unseparated by CPR) to a single shock protocol and a greater emphasis on high-quality CPR between shocks. Many defibrillation studies pre-date this change and so are less relevant.If the shock energy is right first time, the resuscitation duration is shortened, and circulation restored more quickly. Amongst witnessed cases, the chance of survival to 30 days decreases with each defibrillation (OR 0.9; 95% CI 0.88-0.92) (Holmen et al, 2017). The duration of the resuscitation attempt, measured from initiation to return of spontaneous circulation (ROSC), also affects neurological outcome. The chance of surviving with good neurological outcome at one month is significantly higher in those achieving ROSC within 5 minutes compared to those who achieve ROSC after more than 31 minutes (AOR 0.04; 95% CI 0.03-0.05) (Matsuyama et al, 2017). It is important to shorten the resuscitation duration by delivering the optimal shock energy on first and subsequent shocks. Research QuestionIs it feasible to conduct a randomised, pragmatic clinical effectiveness trial in UK ambulance services to identify the optimal energy for defibrillation? AimsThe aims of this feasibility study are to explore the following to inform the design and processes in a full randomised controlled trial (RCT): 1. Number of eligible patients and the recruitment rate 2. Acceptability to paramedics of randomisation of the intervention 3. Practicality of obtaining data downloads from defibrillators 4. Practicality of obtaining other outcome data such as mRS scores (a measure of neurological disability) to 30 days post event Timelines for delivery Work package 1 (months 1-12): To ensure that the feasibility study is well informed, I will conduct a systematic review of the literature. Work package 2 (months 13-48): A feasibility study. I aim to recruit 40-60 patients from one ambulance service. I will explore associated difficulties and how to overcome these. Anticipated impact & dissemination The aim of a large RCT would be to improve patient survival rates and decrease myocardial damage, by determining the minimum shock energy required to achieve a successful outcome. Conducting this feasibility study would inform the design of a full trial. Through my supervisors I would keep guideline writing bodies informed of the study. This would facilitate timely integration of results of any future trial.

Lay Abstract: Background Each year, the UK ambulance services attempt to restart the hearts of 30,000 people who have suffered cardiac arrest (when the heart stops beating). Performance of good chest compressions (CPR) and, where appropriate, delivery of an electric shock to the heart (defibrillation) are the only proven methods of reviving these patients. The purpose of delivering an electric shock is to kick-start the heart back into beating normally. Electric shock machines, known as defibrillators, can deliver a range of electric shock strengths (e.g. low, medium and high). However, we don't presently know the best shock strength to start with and whether subsequent shocks should be increased. Giving an electric shock that is too high risks damaging the heart whilst one that is too low may not restart the heart. Because no one knows what the best shock strength is, UK ambulance services all do something a bit different.When the effects of different treatments are not known, researchers may conduct a clinical trial to find out. Trials of this type are usually large, so it is necessary to first find out whether these tests are possible and anticipate any problems. Conducting a 'feasibility study' helps to ensure that time and money are well spent on a full-scale trial. Aim of the research 	to conduct a feasibility trial to provide the information needed to design a full clinical trial. 	to know whether ambulance staff would be prepared to test different shock strengths and how easy it would be to gather information from defibrillators. 	to find out how easy it would be to collect information about the patients' condition after they have left ambulance service care. 	 	Design and methods 	 	For the feasibility trial I will:	 	put patients into different groups to receive different shock strategies (either using the same or increasing shock strengths). None of these shock strengths will be any higher or lower than currently used in UK ambulance services. All other treatments and care will be given in the usual way. 	find out whether ambulance staff follow the shock strategy requested and looking at information recorded by defibrillators to see the actual shock strengths given. 	use ambulance service records to find out about other care and the patients' condition. 	find how many patients could have been included by looking at ambulance service 999 call records and compare this to the actual number included to find the 'recruitment rate'. 	seek information from hospital records to find out what happened to patients in hospital and for the following 30 days.	 	I aim to include 40-60 patients in this feasibility trial. Where I find difficulties, I will explore how I can reduce these difficulties so that the full clinical trial will work. 	 	Patient and public involvement 	 	Members of South Central Ambulance Service's Patient Forums strongly support this research. They have helped design the research so it is relevant to patients. They provided guidance on how to best communicate information about the trial and how to approach consent. We jointly prepared this lay summary. Going forwards, two members will join a 'Trial Steering Committee' which will closely watch how this project is run.	 	Letting people know the results 	 	I will work with our public representatives to let people know about this project. We will speak together at professional meetings and community group meetings. Doctors and other health workers will be told about the results through articles in their professional magazines. I will take advice from our public representatives about good ways to reach large numbers of the public.

Research Activity Codes: 6.3 MEDICAL DEVICES
Health Categories: CARDIOVASCULAR