title: The association between a quantitative computed tomography (CT) measurement of cerebral edema and outcomes in post-cardiac arrest-a validation study.
abstract: OBJECTIVE
  Previous studies have examined the association between quantitative head computed tomography (CT) measures of cerebral edema and patient outcomes reporting that a calculated gray matter to white matter attenuation ratio (GWR) of <1.2 indicates a near 100% non-survivable injury post-cardiac arrest. The objective of the current study was to validate whether a GWR <1.2 reliably indicates poor survival post-cardiac arrest. We also sought to determine the inter-rater variability among reviewers, and examine the utility of a novel GWR measurement to facilitate easier practical use.
  
  
  METHODS
  We performed a retrospective analysis of post-cardiac arrest patients admitted to a single center from 2008 to 2012. Inclusion criteria were age ≥18 years, non-traumatic arrest, and available CT imaging within 24h after ROSC. Three independent physician reviewers from different specialties measured CT attenuation of pre-specified gray and white matter areas for GWR calculations.
  
  
  RESULTS
  Out of 171 consecutive patients, 90 met the study inclusion criteria. Thirteen patients were excluded for technical reasons and/or significant additional pathology, leaving 77 head CT scans for evaluation. Median age was 66 years and 64% were male. In-hospital mortality was 65% and 70% of patients received therapeutic hypothermia. For the validation measurement, the intra-class correlation coefficient was 0.70. In our dataset, a GWR below 1.2 did not accurately predict mortality or poor neurological outcome (sensitivity 0.56-0.62 and specificity 0.63-0.81). A score below 1.1 predicted a near 100% mortality but was not a sensitive metric (sensitivity 0.14-0.20 and specificity 0.96-1.00). Similar results were found for the exploratory model.
  
  
  CONCLUSIONS
  A GWR <1.2 on CT imaging within 24h after cardiac arrest was moderately specific for poor neurologic outcome and mortality. Based on our data, a threshold GWR <1.1 may be a safer cut-off to identify patients with low chance of survival and good neurological outcome. Intra-class correlation among reviewers was moderately good.
authors.affiliation: Department of Emergency Medicine, Beth Israel Deaconess Medical Center, Boston, MA, United States. Electronic address: cristal.cristia@gmail.com.
authors.forename: Cristal
authors.initials: C
authors.lastname: Cristia
authors.affiliation: Department of Radiology, Beth Israel Deaconess Medical Center, Boston, MA, United States. Electronic address: mailanho@yahoo.com.
authors.forename: Mai-Lan
authors.initials: ML
authors.lastname: Ho
authors.affiliation: Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA, United States. Electronic address: sdlevy@bidmc.harvard.edu.
authors.forename: Sean
authors.initials: S
authors.lastname: Levy
authors.affiliation: Department of Emergency Medicine, Beth Israel Deaconess Medical Center, Boston, MA, United States; Department of Anesthesiology, Aarhus University Hospital, Aarhus, Denmark. Electronic address: lwanders@bidmc.harvard.edu.
authors.forename: Lars W
authors.initials: LW
authors.lastname: Andersen
authors.affiliation: Department of Emergency Medicine, University of Colorado School of Medicine, CO, United States. Electronic address: sarah.perman@ucdenver.edu.
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Perman
authors.affiliation: Department of Emergency Medicine, Beth Israel Deaconess Medical Center, Boston, MA, United States. Electronic address: t.a.giberson@gmail.com.
authors.forename: Tyler
authors.initials: T
authors.lastname: Giberson
authors.affiliation: Department of Emergency Medicine, Beth Israel Deaconess Medical Center, Boston, MA, United States. Electronic address: justin.salciccioli@gmail.com.
authors.forename: Justin D
authors.initials: JD
authors.lastname: Salciccioli
authors.affiliation: Department of Emergency Medicine, Beth Israel Deaconess Medical Center, Boston, MA, United States. Electronic address: bsaindon@bu.edu.
authors.forename: Brian Z
authors.initials: BZ
authors.lastname: Saindon
authors.affiliation: Department of Emergency Medicine, Beth Israel Deaconess Medical Center, Boston, MA, United States; Department of Anesthesia Critical Care, Beth Israel Deaconess Medical Center, Boston, MA, United States. Electronic address: mcocchi@bidmc.harvard.edu.
authors.forename: Michael N
authors.initials: MN
authors.lastname: Cocchi
authors.affiliation: Department of Emergency Medicine, Beth Israel Deaconess Medical Center, Boston, MA, United States; Department of Medicine, Division of Critical Care, Beth Israel Deaconess Medical Center, Boston, MA, United States. Electronic address: mdonnino@bidmc.harvard.edu.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Donnino
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001929:Brain Edema / Q000000981:diagnostic imaging* / Q000209:etiology*; D005260:Female; D006323:Heart Arrest / Q000150:complications*; D006801:Humans; D008297:Male; D008875:Middle Aged; D059906:Neuroimaging; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
keywords: CT; Cardiac arrest; Cerebral edema; Computed tomography; Post-cardiac arrest; Prognostication