title: Understanding traumatic shock: out-of-hospital hypotension with and without other physiologic compromise.
abstract: BACKGROUND
  Among trauma patients with out-of-hospital hypotension, we evaluated the predictive value of systolic blood pressure (SBP) with and without other physiologic compromise for identifying trauma patients requiring early critical resources.
  
  
  METHODS
  This was a secondary analysis of a prospective cohort of injured patients 13 years or older with out-of-hospital hypotension (SBP ≤ 90 mm Hg) who were transported by 114 emergency medical service agencies to 56 Level I and II trauma centers in 11 regions of the United States and Canada from January 1, 2010, through June 30, 2011. The primary outcome was early critical resource use, defined as blood transfusion of 6 U or greater, major nonorthopedic surgery, interventional radiology, or death within 24 hours.
  
  
  RESULTS
  Of 3,337 injured patients with out-of-hospital hypotension, 1,094 (33%) required early critical resources and 1,334 (40%) had serious injury (Injury Severity Score [ISS] ≥ 16). Patients with isolated hypotension required less early critical resources (14% vs. 52%), had less serious injury (20% vs. 61%), and had lower mortality (24 hours, 1% vs. 26%; in-hospital, 3% vs. 34%). The standardized probability of requiring early critical resources was lowest among patients with blunt injury and isolated moderate hypotension (0.12; 95% confidence interval, 0.09-0.15) and steadily increased with additional physiologic compromise, more severe hypotension, and penetrating injury (0.94; 95% confidence interval, 0.90-0.98).
  
  
  CONCLUSIONS
  A minority of trauma patients with isolated out-of-hospital hypotension require early critical resuscitation resources. However, hypotension accompanied by additional physiologic compromise or penetrating injury markedly increases the probability of requiring time-sensitive interventions.
  
  
  METHODS
  Prognostic study, level II.
authors.affiliation: From the Center for Policy and Research in Emergency Medicine (C.D.N., D.R.), Department of Emergency Medicine, and Department of Surgery (M.S.), Oregon Health & Science University, Portland, Oregon; Department of Biostatistics (E.N.M., B.M.), and Clinical Trials Center (D.K.), and Department of Surgery (E.M.B.), University of Washington, Seattle, Washington; Department of Emergency Medicine (D.R.), San Francisco General Hospital, University of California-San Francisco, San Francisco, California; Department of Surgery (K.B.), Medical College of Wisconsin, Milwaukee, Wisconsin; Department of Surgery (J.D.K.), University of Alabama at Birmingham, Birmingham, Alabama; and Rescu (I.R.D.), Li Ka Shing Knowledge Institute, St. Michael's Hospital, Institute of Medical Science, University of Toronto, Toronto; and Department of Emergency Medicine (M.A.), The Ottawa Hospital, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Craig D
authors.initials: CD
authors.lastname: Newgard
authors.forename: Eric N
authors.initials: EN
authors.lastname: Meier
authors.forename: Barbara
authors.initials: B
authors.lastname: McKnight
authors.forename: Ian R
authors.initials: IR
authors.lastname: Drennan
authors.forename: Derek
authors.initials: D
authors.lastname: Richardson
authors.forename: Karen
authors.initials: K
authors.lastname: Brasel
authors.forename: Martin
authors.initials: M
authors.lastname: Schreiber
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Kerby
authors.forename: Delores
authors.initials: D
authors.lastname: Kannas
authors.forename: Michael
authors.initials: M
authors.lastname: Austin
authors.forename: Eileen M
authors.initials: EM
authors.lastname: Bulger
mesh_terms: D000293:Adolescent; D000328:Adult; D002170:Canada / Q000453:epidemiology; D004632:Emergency Medical Services; D005260:Female; D006302:Health Services Research; D006801:Humans; D007022:Hypotension / Q000453:epidemiology / Q000503:physiopathology* / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D010043:Outcome and Process Assessment, Health Care; D011446:Prospective Studies; D012042:Registries; D012151:Resuscitation / Q000379:methods*; D012774:Shock, Traumatic / Q000453:epidemiology / Q000503:physiopathology* / Q000628:therapy*; D014193:Trauma Centers; D014481:United States / Q000453:epidemiology