title: Identifying life-threatening shock in the older injured patient: an analysis of the National Trauma Data Bank.
abstract: OBJECTIVE
  Reliance on traditional vital signs (TVS), particularly in older patients, to identify life-threatening shock after injury may be unreliable. Shock index (SI), defined as heart rate divided by systolic blood pressure (SBP), may be a better indicator of early shock after injury than TVS. Multiplying age by SI (age x SI) may be better in older injured patients. We hypothesized that age x SI would be a better predictor of 48-hour mortality in old patients (age, >55 years) compared with TVS, whereas for young patients (age, <or=55 years), SI would be a better predictor than TVS.
  
  
  METHODS
  Version 8.1 of the National Trauma Data Bank was queried for incidents of blunt, non-neurologic injury occurring during 2007, to patients aged 18 to 81 years. Areas under the receiver operating characteristic curves (AUC) were compared for TVS, SI, and age x SI in young and old patients for predicting 48-hour mortality.
  
  
  RESULTS
  A total of 189,574 incidents were identified. Overall 48-hour mortality was 1.18%. For young patients, there was no difference between SBP (AUC, 0.654) and SI (AUC, 0.655) for predicting 48-hour mortality. For old patients, age x SI (AUC, 0.693) was a better predictor of 48-hour mortality compared with heart rate (AUC, 0.626; p < 0.0001), SBP (AUC, 0.657; p < 0.0002), or SI (AUC, 0.684; p < 0.008).
  
  
  CONCLUSIONS
  TVS are inadequate predictors of shock after non-neurologic blunt injury. Using SI in the young and age x SI in old to identify patients at risk for early mortality after blunt injury could result in earlier definitive treatment.
authors.affiliation: Department of Surgery, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA. bzarzaur@utmem.edu
authors.forename: Ben L
authors.initials: BL
authors.lastname: Zarzaur
authors.forename: Martin A
authors.initials: MA
authors.lastname: Croce
authors.forename: Louis J
authors.initials: LJ
authors.lastname: Magnotti
authors.forename: Timothy C
authors.initials: TC
authors.lastname: Fabian
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000367:Age Factors; D000368:Aged / Q000706:statistics & numerical data*; D001794:Blood Pressure; D016208:Databases, Factual; D005260:Female; D006339:Heart Rate; D017052:Hospital Mortality; D006801:Humans; D015994:Incidence; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011379:Prognosis; D012189:Retrospective Studies; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D012771:Shock, Hemorrhagic / Q000175:diagnosis* / Q000209:etiology / Q000401:mortality* / Q000503:physiopathology; D018709:Statistics, Nonparametric; D013599:Systole; D013997:Time Factors; D014481:United States / Q000453:epidemiology; D014949:Wounds, Nonpenetrating / Q000150:complications / Q000453:epidemiology