title: Arterial hyperoxia and mortality in critically ill patients: a systematic review and meta-analysis.
abstract: BACKGROUND
  The safety of arterial hyperoxia is under increasing scrutiny. We performed a systematic review of the literature to determine whether any association exists between arterial hyperoxia and mortality in critically ill patient subsets.
  
  
  METHODS
  Medline, Thomson Reuters Web of Science and Scopus databases were searched from inception to June 2014. Observational or interventional studies evaluating the relationship between hyperoxia (defined as a supranormal arterial O2 tension) and mortality in adult intensive care unit (ICU) patients were included. Studies primarily involving patients with exacerbations of chronic pulmonary disease, acute lung injury and perioperative administration were excluded. Adjusted odds ratio (OR) of patients exposed versus those not exposed to hyperoxia were extracted, if available. Alternatively, unadjusted outcome data were recorded. Data on patients, study characteristics and the criteria used for defining hyperoxia exposure were also extracted. Random-effects models were used for quantitative synthesis of the data, with a primary outcome of hospital mortality.
  
  
  RESULTS
  In total 17 studies (16 observational, 1 prospective before-after) were identified in different patient categories: mechanically ventilated ICU (number of studies (k) = 4, number of participants (n) = 189,143), post-cardiac arrest (k = 6, n = 19,144), stroke (k = 2, n = 5,537), and traumatic brain injury (k = 5, n = 7,488). Different criteria were used to define hyperoxia in terms of PaO2 value (first, highest, worst, mean), time of assessment and predetermined cutoffs. Data from studies on ICU patients were not pooled because of extreme heterogeneity (inconsistency (I(2)) 96.73%). Hyperoxia was associated with increased mortality in post-cardiac arrest patients (OR = 1.42 (1.04 to 1.92) I(2) 67.73%) stroke (OR = 1.23 (1.06 to 1.43) I(2) 0%) and traumatic brain injury (OR = 1.41 (1.03 to 1.94) I(2) 64.54%). However, these results are limited by significant heterogeneity between studies.
  
  
  CONCLUSIONS
  Hyperoxia may be associated with increased mortality in patients with stroke, traumatic brain injury and those resuscitated from cardiac arrest. However, these results are limited by the high heterogeneity of the included studies.
authors.affiliation: Anaesthesia and Intensive Care Unit, Department of Biomedical Sciences and Public Health, Università Politecnica delle Marche, via Tronto 10, 60126, Torrette di Ancona, Italy. eli.dam86@alice.it.
authors.forename: Elisa
authors.initials: E
authors.lastname: Damiani
authors.affiliation: Anaesthesia and Intensive Care Unit, Department of Biomedical Sciences and Public Health, Università Politecnica delle Marche, via Tronto 10, 60126, Torrette di Ancona, Italy. e.adrario@univpm.it.
authors.forename: Erica
authors.initials: E
authors.lastname: Adrario
authors.affiliation: Department of Anaesthesia and Intensive Care, University Hospital of Modena, Via del Pozzo 71, 41124, Modena, Italy. girardis.massimo@unimo.it.
authors.forename: Massimo
authors.initials: M
authors.lastname: Girardis
authors.affiliation: Anaesthesia and Intensive Care Unit, Department of Biomedical Sciences and Public Health, Università Politecnica delle Marche, via Tronto 10, 60126, Torrette di Ancona, Italy. viboval@yahoo.it.
authors.forename: Rocco
authors.initials: R
authors.lastname: Romano
authors.affiliation: Anaesthesia and Intensive Care Unit, Department of Biomedical Sciences and Public Health, Università Politecnica delle Marche, via Tronto 10, 60126, Torrette di Ancona, Italy. p.pelaia@univpm.it.
authors.forename: Paolo
authors.initials: P
authors.lastname: Pelaia
authors.affiliation: Bloomsbury Institute of Intensive Care Medicine, University College London, Gower Street, London, WC1E 6BT, UK. m.singer@ucl.ac.uk.
authors.forename: Mervyn
authors.initials: M
authors.lastname: Singer
authors.affiliation: Anaesthesia and Intensive Care Unit, Department of Biomedical Sciences and Public Health, Università Politecnica delle Marche, via Tronto 10, 60126, Torrette di Ancona, Italy. a.donati@univpm.it.
authors.forename: Abele
authors.initials: A
authors.lastname: Donati
mesh_terms: D062186:Arterial Pressure / Q000502:physiology; D001784:Blood Gas Analysis / Q000379:methods; D016638:Critical Illness / Q000401:mortality*; D017052:Hospital Mortality / Q000639:trends*; D006801:Humans; D018496:Hyperoxia / Q000175:diagnosis / Q000401:mortality* / Q000503:physiopathology; D064887:Observational Studies as Topic / Q000379:methods; D011446:Prospective Studies