Design and publication of this study were approved by the scientific committee of the GRR and the TR-DGU in compliance with current publication guidelines. This study was approved by the ethics committee of the University of Cologne, Faculty of Medicine (Kerpener Str. 62, 50937 Cologne, Germany) (Register Number 11-014) and the ethics committee of the Belinostat ptcl University of Kiel, Faculty of Medicine (Schwanenweg 20,24105 Kiel, Germany) (Register Number D456/11).Materials and methodsGerman Resuscitation Registry (GRR)The GRR currently represents 51 emergency medical systems that record data on out-of-hospital CPR attempts throughout the country, covering a population of nine million citizens (the total population of Germany is 85 million). Participation is voluntary.

In Germany, emergency medical systems (EMS) are staffed by emergency physicians from several medical specialties (mainly anesthesiology, surgery, and internal medicine) who had additional training in emergency medicine. The registry is organized and funded by the DGAI [8].The GRR is divided into two different data sets. Firstly, a ‘preclinical care’ data set derived from the Utstein-style template for uniform reporting of cardiac arrest, aiming at documentation of pre-hospital logistic issues, presumed aetiology, resuscitation therapy and the patient’s initial outcome, including 118 variables. Secondly, the ‘post-resuscitation care’ data set is aimed at documenting in-hospital post-resuscitation efforts. Due to the anonymity of data collection and the fact that the primary purpose of the GRR is quality control, patient consent was not necessary [1].

ROSC was defined as a palpable pulse for more than 20 seconds [9,10]. Admission to hospital (ATH) was regarded as a positive outcome if circulation was still present on hospital admission (group AGRR). Failure of pre-hospital ROSC or ongoing CPR on admission was defined as a negative outcome (no ROSC/no ATH; group B).Within the GRR 13,329 out-of-hospital cardiac arrest patients were prospectively documented between 1998 and 2010 for which a professional pre-hospital EMS team was requested by dispatchers. The present study includes 368 patients (2.8%) with cardiac arrest most probably due to traumatic cause; 3673 cardiac arrest patients with a cardiac cause and with ROSC at hospital admission served as a ‘cardiac control group’ (group C).

Patients from the GRR were divided into the following three groups:? group AGRR: pre-hospital CPR with ATH (n = 95)? group B: pre-hospital CPR without ROSC/ATH (n = 273)? group C: cardiac control group with ROSC (n = 3,673).Trauma Registry of the Cilengitide German Society for Trauma Surgery (TR-DGU)The TR-DGU is a prospective structured database established in 1993. Participation has been voluntary until recently, when it became an obligatory tool for quality assessment in regional trauma networks [11].