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Table 1 Characteristics of included studies

From: Anion gap as a prognostic tool for risk stratification in critically ill patients – a systematic review and meta-analysis

First author/year Nr Country Setting and most frequent reasons for admission Study design Age (mean or mdn) Sample size Male (%) Outcome (mortality) Total mortality (%) Severity of illness (mean score ± SD or mdn and range or IQR)
Antonini 2008 [17] 1 Italy General ICU admissions: 36 % trauma; 26 % cerebrovascular disease; 14 % sepsis Pro Mean: 53 136 71 28-day 27 SOFA: 6 (range 0–18)
SAPS II: 40 (range 6–76)
Attanà 2013 [18] 2 Italy STEMI patients with persistent cardiogenic shock after primary PCI admitted to ICCU Pro Mean: 73 63 62 In-ICCU 49 APACHE II: 20.6 ± 12.4
Boniatti 2011 [27] 3 Brazil General ICU admissions: 64 % medical admissions; 27 % sepsis; 24 % elective surgery; 12 % emergency surgery Pro Mean: 56 175 53 In-hospital 37 APACHE II: 20.8 ± 8.0
SOFA score: 6.2 ± 3.8
Cusack 2002 [19] 4 UK General ICU admissions: 17 % respiratory failure; 11 % post-cardiac arrest; 8 % trauma Pro Mean: 61 100 NA 28-day 31 APACHE II: 20.5
Dondorp 2004 [29] 5 Vietnam Patients with severe falciparum malaria admitted to ICU Pro Mdn: 31 268 80 Not defined 17 GCS < 11: 51 %
8 % Haemodynamic shocka
Dubin 2007 [37] 6 Argentina General ICU admissions: 56 % medical admissions; 35 % elective surgery; 9 % emergency surgery Pro Mean: 65 935 49 30-day 11 APACHE II: 13 ± 7
SOFA: 3 ± 3
FitzSullivan 2005 [20] 7 USA Trauma ICU admissions: 60 % blunt trauma Retro Mean: 36 3102 81 In-hospital 17 APACHE II: 26.1 ± 10.5
ISS: 20.4 ± 12.9
Hucker 2005 [21] 8 UK A&E admissions: 46 % medical admissions; 17 % elderly care; 16 % discharged Pro Mean: 67 672 NA In-hospital 12 93 % alert on AVPU scale
Kaplan 2004 [7] 9 USA Trauma patients requiring vascular repair of torso or extremities, trauma centre: 83 % penetrating trauma Retro Mean: 32 282 NA 28-day 23 ISS: 15.8 ± 11.0
Kaplan 2008 [16] 10 USA Major trauma patients, trauma centre: 59 % blunt trauma Retro Mean: 33 78 44 28-day in hospital 33 ISS: 8.9 ± 7.3
Lazzeri 2010 [22] 11 Italy STEMI patients admitted to ICCU at tertiary centre undergoing primary PCI Pro Mdn: 67 445 75 In-hospital 10 92 % Killip class I-II
8 % Killip class II-IV
41 % complications in ICCU
Lipnick 2013 [13] 12 USA General ICU admissions: 57 % medical; 44 % surgical; 16 % sepsis Retro Mean: 65 664 55 30-day 15 33 % no organ failure
53 % 1–2 organs failed
14 %% ≥ 3 organs failedb
Martin 2013 [23] 13 Germany Surgical ICU admissions: 17 % maxillofacial surgery; 13 % ENT; 12 % neurosurgery Retro Mean: 59 1551 54 In-hospital 9 Average length of stay in ICU: 4.2 days
Martin 2005a [25] 14 USA Surgical ICU admissions: 56 % abdominal; 18 % vascular; 10 % thoracic Retro Mean: 52 2291 61 In-ICU 8 APACHE II: 21.8 ± 9.7
SAPS: 16.8 ± 8.8
Martin 2005b [24] 15 USA Trauma patients, trauma centre: 65 % blunt trauma Retro Mean: 38 427 79 In-hospital 10 ISS: 23 ± 23
Novovic 2014 [28] 16 Serbia ICU patients requiring mechanical ventilation Retro Mean: 60 142 47 28-day 52 APACHE II: 16.2 ± 6.4
Rocktaeschel 2003 [8] 17 Australia General ICU admissions: 91 % respiratory; 54 % gastrointestinal; 51 % cardiovascular Retro Mdn: 65 300 58 In-hospital 28 APACHE II: 17 (IQR 14 – 22)
Sahu 2006 [26] 18 USA Patients with acute MI admitted to coronary care unit: 65 % STEMI Retro Mean: 63 773 62 In-hospital 11 5 % cardiogenic shock
Shane 2014 [30] 19 Uganda Major trauma patients, trauma centre: 65 % road traffic accidents; 35 % assault Pro Mean: 26 93 81 In-hospital 34 ISS: 25.4 ± 8.3
  1. APACHE II Acute Physiology and Chronic Health Evaluation, AVPU alert, verbal, pain, unresponsive, ENT ear, nose and throat, GCS Glasgow coma scale, ICCU intensive cardiac care unit, ICU intensive care unit, IQR interquartile range, ISS Injury Severity Score, Mdn median, MI myocardial infarction, PCI percutaneous coronary intervention, Pro prospective, Retro retrospective, SAPS simplified acute physiology score, SD standard deviation, SOFA sequential organ failure assessment, STEMI ST-elevation myocardial infarction
  2. aBased on data of previously published original study including 346 patients [38]
  3. bBased on data from entire study cohort of 18,995 patients