Pre-hospital critical care for out of hospital cardiac arrest

Does it work, how does it work and how much does it cost?

Chief Investigator	Institution	Dates	Funding Stream	Grant Ref	Amount
Von Vopelius Feldt, Johannes	University Hospitals Bristol NHS Foundation Trust	01/01/2016-31/12/2018 (36 months) + 3 months	NIHR Doctoral Research Fellowship	DRF-2015-08-040	£217,279

Background

Despite remarkable efforts to improve both pre-hospital and in-hospital care, survival from out of hospital cardiac arrest (OHCA) remains poor. Certain prehospital interventions, such as high quality bystander cardio-pulmonary resuscitation (CPR) and early defibrillation, have been shown to improve survival from OHCA. Scientific evidence also supports the concept of prehospital advanced life support (ALS), and all registered paramedics in the UK are now ALS-certified. Current research regarding any further benefits from the dispatch of pre-hospital critical care teams (CCTs) to OHCA has produced conflicting results. A pilot study undertaken by the applicant suggested a potential improvement in survival to hospital discharge after OHCA from 8.9% to 13.2% when comparing ALS-trained paramedics to a CCT.

Aims

Given this potential for a significant benefit from CCTs, we aim to answer the following questions:

- Can this effect be demonstrated to be both clinically and statistically significant in a larger sample, and across several ambulance trusts in the UK?

- Which intervention(s) delivered by a CCT have the strongest survival benefit?

- What is the cost effectiveness of a CCT in OHCA?

- What are the barriers to a randomised clinical trial to address this research question, and how might they be overcome.

Methods

A number of ambulance trusts in the UK dispatch CCTs to suspected or confirmed OHCA. While the CCTs will aim to attend most cases of OHCA, they will inevitably be unavailable for some cases, due to already having been dispatched to another case of critical illness or injury, or the limitations imposed by operational duty hours and constrained funding. This results in a natural experiment where one group of patients is attended by a CCT and another is treated by ALS-trained paramedics only. Within the South Western Ambulance Trust (SWAST), the CCT attends approximately 10% of OHCA cases.

All NHS ambulance trusts routinely collect data on all OHCA patients, including survival to hospital discharge, which is a national ambulance quality indicator. We will prospectively collect OHCA data from four NHS ambulance trusts over an 18-month period and analyse the effect of pre-hospital critical care on survival to hospital discharge between the two groups by matching OHCA cases with CCT care to controls treated by ALS-trained paramedics alone. This will be done using propensity score matching, variables will include location of OHCA, age of patient, bystander CPR, ambulance response time, initial cardiac rhythm and characteristics of designated receiving hospital.

We will use multiple logistic regression to examine the association between the actual interventions delivered during pre-hospital care and survival to hospital discharge, with the aim to better understand the complex intervention that is pre-hospital critical care.

As a next step, we will calculate the costs of providing pre-hospital critical care, following a published framework for the cost analysis of emergency medical services (EMS), in order to determine the cost-effectiveness of prehospital CCTs.

We have explored the possibility of answering the study question through a randomised controlled trial (RCT) but the associated costs, logistical challenges, patient and public involvment (PPI) advice and ethical concerns favor an observational study design at this stage. Nevertheless, we will undertake a nested qualitative study, using focus group interviews in five key stakeholder groups, to identify the potential barriers to a RCT to address this research question, and ways to overcome these barriers.

Potential benefits

The results of this study will help to understand the effect of a pre-hospital CCT on survival from OHCA. They will also inform decision-making regarding the commissioning, funding and dispatch of pre-hospital CCTs with the potential to significantly improve outcomes from OHCA whilst offering clinically effective and cost-effective care.