Table 2.

Primary study characteristics

	Study	Country	Journal	Study design	Database	Start patient inclusion	Stop patient inclusion	Total number of patients in study	Number of patients included in meta-analysis	Trauma type
1	Aoki et al. [39]	Japan	Scientific Reports (Nature)	Retrospective cohort study with post-hoc case–control analysis	All-Japan Utstein Registry	01–2012	12–2015	465.932	5.204	Blunt
2	Barnard et al. [28]	UK	Resuscitation	Retrospective cohort	TARN (Trauma Audit and Research Network	01–2009	09–2015	227.944	576	Both
3	Barnard et al. [40]	UK	Emergency Medical Journal	Retrospective cohort	EEAST (East of UK Ambulance Service NHS Trust)	01–2015	07–2017	9.109	304	Both
4	Beck et al. [1]	Australia	Resuscitation	Retrospective cohort	SJA-WHA (St John Ambulance Western Australia)	01–1997	12–2014	21.071	1.354	Both
5	Beck et al. [29]	Australia	Emergency Medical Journal + Resuscitation	Retrospective cohort	VACAR (Victorian Ambulance Cardiac Arrest Registry)	07–2008	06–2014	2.334	660	Both
6	Chen et al. [41]	Taiwan	Injury	Retrospective cohort	5 local hospitals	01–2010	12–2014	560	463	Both
7	Chia et al. [30]	Singapore, Malaysia, Japan and Thailand	Resuscitation	Retrospective cohort	PAROS (Pan-Asian Resuscitation Outcomes Study)	01–2009	12–2012	66.780	1.554	Both
8	Chiang et al. [31]	Taiwan	Emergency Medical Journal	Retrospective cohort	Taipei Fire City Department	01–2009	12–2013	921	893	Blunt
9	Claesson et al. [32]	Sweden	Resuscitation	Retrospective cohort	SRCR (Swedish Registry of Cardiopulmonary Resuscitation)	01–2004	12–2014	70.846	1.553	Both
10	Cureton et al. [23]	USA	Journal of Trauma and Acute Care Surgery	Retrospective cohort	Local hospital	01–2002	09–2008	318	318	Both
11	David et al. [19]	France and Belgium	Critical Care Medicine	Randomized controlled trial	12 local hospitals	01–1994	09–1996	2.910	268	Both
12	Deasy et al. [24]	Australia	Resuscitation	Retrospective cohort	VACAR (Victorian Ambulance Cardiac Arrest Registry)	01–2000	12–2009	33.178	2.187	Both
13	Di Bartolomeo et al. [6]	Italy	Prehospital Emergency Care	Prospective population-based study	Local FVG (Friuli Venezia Giulia)	01–1998	02–1999	181	129	Both
14	Djarv et al. [35]	Sweden	Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine	Retrospective cohort	SRCR (Swedish Registry of Cardiopulmonary Resuscitation)	01–1990	12–2016	72.547	1.774	Both
15	Duchateau et al. [33]	France	Emergency Medical Journal	Retrospective cohort	3 local hospitals	01–2010	01–2013	88	88	Both
16	Escutnaire et al. [36]	France	Resuscitation	Retrospective cohort	RéAC (French National Cardiac Arrest Registry)	07–2011	01–2017	60.157	3.209	Both
17	Evans et al. [27]	USA and Canada	Journal of Trauma Acute Care Surgery	Retrospective cohort	ROC trauma registries	12–2005	06–2011	19.549	2.300	Both
18	Faucher et al. [21]	France	Annales françaises d'anesthesie et de réanimation	Retrospective cohort	Local regional database	01–2004	12–2005	1.552	129	Both
19	Fukuda et al. [37]	Japan	JAMA Surgery	Retrospective cohort	All-Japan Utstein Registry	01–2013	12–2014	251.075	4.382	Blunt
20	Gräsner et al. [2]	Germany	Critical Care Medicine	Retrospective cohort	TR-DGU (Trauma Registry of German Society for Trauma Surgery)	01–1993	12–2009	26.180	814	Both
21	Huber-Wagner et al. [20]	Germany, Austria and Switzerland	Resuscitation	Retrospective cohort	TRGTS (Trauma Registry of the German Trauma Society)	01–1993	12–2004	10.359	757	Both
22	Irfan et al. [34]	Qatar	International Journal of Cardiology	Retrospective cohort	Hamad Trauma Centre	01–2010	12–2015	718	410	Both
23	Israr et al. [42]	USA	Injury	Retrospective cohort	2 Lvl 1 hospitals in Arizona	02–2013	12–2017	277	277	Both
24	Javaudin et al. [46]	France	Prehospital Emergency Care	Retrospective cohort	French National OHCA Registry (RéAC)	07–2011	06–2018	82.125	2.981	Both
25	Jun et al. [47]	Korea	Clinical and Experimental Emergency Medicine	Retrospective cohort	Out-of-Hospital Cardiac Arrest Surveillance (OHCAS) of the KCDC	01–2012	12–2016	142.905	8.237	Both
26	Kitamura et al. [26]	Japan	British Medical Journal Open	Retrospective cohort	Utstein Osaka Project	01–2005	12–2011	47.735	2.065	Blunt
27	Lin et al. [25]	Taiwan	Resuscitation	Retrospective cohort	Utstein-style population database	01–2004	12–2010	3.607	424	Both
28	Lockey et al. [3]	UK	Annals of Emergency Medicine	Retrospective cohort	London HEMS database	07–1994	06–2004	12.086	909	Both
29	Lu et al. [43]	Taiwan	Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine	Retrospective cohort	Local EMS database	01–2014	12–2016	4.526	560	Both
30	Moriwaki et al. [22]	Japan	World Journal of Surgery	Retrospective cohort	Local Hospital	2000	2010	477	477	Blunt
31	Pickens et al. [17]	USA	Journal of Trauma: Injury, Infection, and Critical Care	Retrospective cohort	Seattle Fire Department	01–1995	04–2001	266	184	Both
32	Stockinger et al. [16]	USA	Journal of American College of Surgeons	Retrospective cohort	Local hospital	01–1997	12–2002	25.489	588	Both
33	ter Avest et al. [44]	UK	Resuscitation	Retrospective cohort	KSSAAT (Kent, Surrey & Sussex Air Ambulance trust)	07–2013	05–2018	263	262	Both
34	Tsutsumi et al. [38]	Japan	Injury	Retrospective cohort	Japan Trauma Data Bank	01–2004	12–2015	236.698	4.313	Blunt
35	Willis et al. [18]	Australia	Injury	Retrospective cohort	VSTR (Victorian State Trauma System)	07–2001	12–2004	5.349	89	Both
36	Yamamoto et al. [45]	Japan	Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine	Prospective observational study with post hoc analysis	Regional EMS database	01–2012	03–2013	16.452	1.030	Both