title: A systematic review and meta-analysis of the association between arterial carbon dioxide tension and outcomes after cardiac arrest.
abstract: Arterial carbon dioxide tension (PaCO2) abnormalities are common after cardiac arrest (CA). Maintaining a normal PaCO2makes physiological sense and is recommended as a therapeutic target after CA, but few studies have examined the association between PaCO2and patient outcomes. This systematic review and meta-analysis aimed to assess the effect of a low or high PaCO2on patient outcomes after CA.
  
  
  
  We searched MEDLINE, EMBASE, CINAHL and Cochrane CENTRAL, for studies that evaluated the association between PaCO2and outcomes after CA. The primary outcome was hospital survival. Secondary outcomes included neurological status at the end of each study's follow up period, hospital discharge destination and 30-day survival. Meta-analysis was conducted if statistical heterogeneity was low.
  
  
  
  The systematic review included nine studies; eight provided sufficient quantitative data for meta-analysis. Using PaCO2cut-points of <35mmHg and >45mmHg to define hypo- and hypercarbia, normocarbia was associated with increased hospital survival (odds ratio [OR] 1.30, 95% confidence interval [CI] 1.23, 1.38). Normocarbia was also associated with a good neurological outcome (cerebral performance category score 1 or 2) compared to hypercarbia (OR 1.69, 95% CI 1.13, 2.51) when the analysis also included an additional study with a slightly different definition for normocarbia (PaCO230-50mmHg).
  
  
  
  From the limited data it appears PaCO2has an important U-shape association with survival and outcomes after CA, consistent with international resuscitation guidelines' recommendation that normocarbia be targeted during post-resuscitation care.
authors.affiliation: Prehospital Resuscitation and Emergency Care Research Unit (PRECRU), School of Nursing, Midwifery and Paramedicine, Curtin University, Bentley, WA, Australia; Royal Perth Hospital, Perth, WA, Australia. Electronic address: nicole.mckenzie@student.curtin.edu.au.
authors.forename: Nicole
authors.initials: N
authors.lastname: McKenzie
authors.affiliation: Prehospital Resuscitation and Emergency Care Research Unit (PRECRU), School of Nursing, Midwifery and Paramedicine, Curtin University, Bentley, WA, Australia; St John Ambulance Western Australia, Belmont, WA, Australia; Royal Perth Hospital, Perth, WA, Australia; Discipline of Emergency Medicine, University of Western Australia, Perth, WA, Australia.
authors.forename: Teresa A
authors.initials: TA
authors.lastname: Williams
authors.affiliation: Prehospital Resuscitation and Emergency Care Research Unit (PRECRU), School of Nursing, Midwifery and Paramedicine, Curtin University, Bentley, WA, Australia; Discipline of Emergency Medicine, University of Western Australia, Perth, WA, Australia.
authors.forename: Hideo
authors.initials: H
authors.lastname: Tohira
authors.affiliation: Prehospital Resuscitation and Emergency Care Research Unit (PRECRU), School of Nursing, Midwifery and Paramedicine, Curtin University, Bentley, WA, Australia; Royal Perth Hospital, Perth, WA, Australia.
authors.forename: Kwok M
authors.initials: KM
authors.lastname: Ho
authors.affiliation: Prehospital Resuscitation and Emergency Care Research Unit (PRECRU), School of Nursing, Midwifery and Paramedicine, Curtin University, Bentley, WA, Australia; St John Ambulance Western Australia, Belmont, WA, Australia; School of Public Health and Preventive Medicine, Monash University, Melbourne, VIC, Australia; Discipline of Emergency Medicine, University of Western Australia, Perth, WA, Australia.
authors.forename: Judith
authors.initials: J
authors.lastname: Finn
mesh_terms: D001158:Arteries; D002245:Carbon Dioxide / Q000097:blood*; D006323:Heart Arrest / Q000401:mortality*; D006801:Humans
chemical_list: D002245:Carbon Dioxide
keywords: Carbon dioxide; Heart arrest; Outcomes assessment