title: Effects of PaCO2 derangements on clinical outcomes after cerebral injury: A systematic review.
abstract: OBJECTIVE
  Partial pressure of arterial carbon dioxide (PaCO2) is a major regulator of cerebral blood flow (CBF). Derangements in PaCO2 have been thought to worsen clinical outcomes after many forms of cerebral injury by altering CBF. Our aim was to systematically analyze the biomedical literature to determine the effects of PaCO2 derangements on clinical outcomes after cerebral injury.
  
  
  METHODS
  We performed a search of Cochrane Library, PUBMED, CINHAL, conference proceedings, and other sources using a comprehensive strategy. Study inclusion criteria were (1) human subjects; (2) cerebral injury; (3) mechanical ventilation post-injury; (4) measurement of PaCO2; and (5) comparison of a clinical outcome measure (e.g. mortality) between different PaCO2 exposures. We performed a qualitative analysis to collate and summarize effects of PaCO2 derangements according to the recommended methodology from the Cochrane Handbook.
  
  
  RESULTS
  Seventeen studies involving different etiologies of cerebral injury (six traumatic brain injury, six post-cardiac arrest syndrome, two cerebral vascular accident, three neonatal ischemic encephalopathy) met all inclusion and no exclusion criteria. Three randomized control trials were identified and only one was considered a high quality study as per the Cochrane criteria for assessing risk of bias. In 13/17 (76%) studies examining hypocapnia, and 7/10 (70%) studies examining hypercapnia, the exposed group (hypercapnia or hypocapnia) was associated with poor clinical outcome.
  
  
  CONCLUSIONS
  The majority of studies in this report found exposure to hypocapnia and hypercapnia after cerebral injury to be associated with poor clinical outcome. However, the optimal PaCO2 range associated with good clinical outcome remains unclear.
authors.affiliation: Department of Emergency Medicine, Cooper University Hospital and Cooper Medical School of Rowan University, Camden, NJ, USA. Electronic address: roberts-brian-w@cooperhealth.edu.
authors.forename: Brian W
authors.initials: BW
authors.lastname: Roberts
authors.affiliation: Department of Emergency Medicine, Cooper University Hospital and Cooper Medical School of Rowan University, Camden, NJ, USA. Electronic address: Karagiannis-Paul@cooperhealth.edu.
authors.forename: Paul
authors.initials: P
authors.lastname: Karagiannis
authors.affiliation: Department of Emergency Medicine, Cooper University Hospital and Cooper Medical School of Rowan University, Camden, NJ, USA. Electronic address: colett58@rowan.edu.
authors.forename: Michael
authors.initials: M
authors.lastname: Coletta
authors.affiliation: Department of Emergency Medicine, Cooper University Hospital and Cooper Medical School of Rowan University, Camden, NJ, USA. Electronic address: Kilgannon-Hope@cooperhealth.edu.
authors.forename: J Hope
authors.initials: JH
authors.lastname: Kilgannon
authors.affiliation: Department of Emergency Medicine, Cooper University Hospital and Cooper Medical School of Rowan University, Camden, NJ, USA. Electronic address: Chansky-Michael@cooperhealth.edu.
authors.forename: Michael E
authors.initials: ME
authors.lastname: Chansky
authors.affiliation: Department of Emergency Medicine, Cooper University Hospital and Cooper Medical School of Rowan University, Camden, NJ, USA; Department of Medicine, Division of Critical Care Medicine (ST), Cooper University Hospital and Cooper Medical School of Rowan University, Camden, NJ, USA. Electronic address: Trzeciak-Stephen@cooperhealth.edu.
authors.forename: Stephen
authors.initials: S
authors.lastname: Trzeciak
mesh_terms: D001784:Blood Gas Analysis; D001927:Brain Diseases / Q000097:blood* / Q000503:physiopathology; D002245:Carbon Dioxide / Q000097:blood*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology*; D016857:Hypocapnia / Q000503:physiopathology*; D010313:Partial Pressure; D011379:Prognosis
chemical_list: D002245:Carbon Dioxide
keywords: Brain injury; Cerebral injury; Head injury; Hypercapnia; Hypocapnia; Partial pressure of arterial carbon dioxide (PaCO(2))