title: Systematic review of the effectiveness of prehospital critical care following out-of-hospital cardiac arrest.
abstract: Improving survival after out-of-hospital cardiac arrest (OHCA) is a priority for modern emergency medical services (EMS) and prehospital research. Advanced life support (ALS) is now the standard of care in most EMS. In some EMS, prehospital critical care providers are also dispatched to attend OHCA. This systematic review presents the evidence for prehospital critical care for OHCA, when compared to standard ALS care.
  
  
  
  We searched the following electronic databases: PubMed, EmBASE, CINAHL Plus and AMED (via EBSCO), Cochrane Database of Systematic Reviews, DARE, Cochrane Central Register of Controlled Trials, NHS Economic Evaluation Database, NIHR Health Technology Assessment Database, Google Scholar and ClinicalTrials.gov. Search terms related to cardiac arrest and prehospital critical care. All studies that compared patient-centred outcomes between prehospital critical care and ALS for OHCA were included.
  
  
  
  The review identified six full text publications that matched the inclusion criteria, all of which are observational studies. Three studies showed no benefit from prehospital critical care but were underpowered with sample sizes of 1028-1851. The other three publications showed benefit from prehospital critical care delivered by physicians. However, an imbalance of prognostic factors and hospital treatment in these studies systematically favoured the prehospital critical care group.
  
  
  
  Current evidence to support prehospital critical care for OHCA is limited by the logistic difficulties of undertaking high quality research in this area. Further research needs an appropriate sample size with adjustments for confounding factors in observational research design.
authors.affiliation: Academic Emergency Department, University Hospitals Bristol NHS Foundation Trust, Upper Maudlin Way, BS2 8HW Bristol, United Kingdom. Electronic address: johannes.vonvopelius-feldt@uwe.ac.uk.
authors.forename: Johannes
authors.initials: J
authors.lastname: von Vopelius-Feldt
authors.affiliation: Faculty of Health & Applied Sciences, University of the West of England, Glenside Campus, BS16 1QY Bristol, United Kingdom.
authors.forename: Janet
authors.initials: J
authors.lastname: Brandling
authors.affiliation: Academic Emergency Department, University Hospitals Bristol NHS Foundation Trust, Upper Maudlin Way, BS2 8HW Bristol, United Kingdom; Emergency Care, University of the West of England, Bristol, United Kingdom.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Benger
mesh_terms: D022561:Advanced Cardiac Life Support / Q000592:standards*; D003422:Critical Care / Q000592:standards*; D004632:Emergency Medical Services / Q000592:standards*; D005260:Female; D006801:Humans; D008297:Male; D064887:Observational Studies as Topic; D058687:Out-of-Hospital Cardiac Arrest / Q000401:mortality / Q000628:therapy*; D017063:Outcome Assessment, Health Care; D011446:Prospective Studies; D011787:Quality of Health Care
keywords: Advanced life support; Air ambulance; EMS; HEMS; Out-of-hospital cardiac arrest; Prehospital critical care