title: Trauma Surge Index: Advancing the Measurement of Trauma Surges and Their Influence on Mortality.
abstract: BACKGROUND
  Increases in trauma patient volume and acuity, such as during mass casualty events, can overwhelm hospitals, potentially worsening patient outcomes. Due to methodological limitations, the effect of trauma surges on clinical outcomes remains unclear, so hospitals have not prepared for such events in an evidence-based manner. The objective of this study was to develop a new measure of hospital capacity strain corresponding to trauma admissions and to examine the relationship between trauma surges and inpatient mortality.
  
  
  METHODS
  Using trauma registry data from hospitals across the United States and Canada (2010 to 2011), we developed the Trauma Surge Index (TSI), a measure of capacity strain that controls for variation in hospital admission volume and patient acuity. Using the TSI and an established definition of mass casualty events, we quantified hospital surges and entered each measure as an exposure variable in separate risk-adjusted mortality models.
  
  
  RESULTS
  Using the TSI method, we observed that patients admitted during high-surge periods display significantly increased mortality compared with patients admitted during low-surge periods (odds ratio [OR] = 2.05; 95% CI, 1.36-3.10), and patients with firearms injuries were particularly at risk (OR = 7.29; 95% CI, 2.13-24.91). Using mass casualty event criteria, we found no difference between the mortality of patients admitted during trauma surges and nonsurge periods (OR = 0.94; 95% CI, 0.88-1.01).
  
  
  CONCLUSIONS
  We demonstrate the TSI, which is a novel method that identified periods of high-capacity strain in hospitals associated with increased trauma patient mortality. Our newly developed TSI method can be implemented by hospitals and trauma systems to examine periods of high-capacity strain retrospectively, identify specific resources that might have been needed, and better direct future investments in an evidence-based manner.
authors.affiliation: Department of Surgery, Indiana University, Indianapolis, IN. Electronic address: pjenkins1@iuhealth.org.
authors.forename: Peter C
authors.initials: PC
authors.lastname: Jenkins
authors.affiliation: Department of Family Medicine, University of Michigan, Ann Arbor, MI.
authors.forename: Caroline R
authors.initials: CR
authors.lastname: Richardson
authors.affiliation: Department of Health Management and Policy, University of Michigan, Ann Arbor, MI; Department of Economics, National Bureau of Economic Research, University of Michigan, Ann Arbor, MI; Center for Healthcare Outcomes and Policy, University of Michigan, Ann Arbor, MI.
authors.forename: Edward C
authors.initials: EC
authors.lastname: Norton
authors.affiliation: Center for Healthcare Outcomes and Policy, University of Michigan, Ann Arbor, MI; Department of Family Medicine, University of Michigan, Ann Arbor, MI.
authors.forename: Colin R
authors.initials: CR
authors.lastname: Cooke
authors.affiliation: Center for Healthcare Outcomes and Policy, University of Michigan, Ann Arbor, MI; Department of Biostatistics, University of Michigan, Ann Arbor, MI.
authors.forename: Mousumi
authors.initials: M
authors.lastname: Banerjee
authors.affiliation: Division of General Surgery, Department of Surgery, University of Toronto, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.
authors.forename: Avery B
authors.initials: AB
authors.lastname: Nathens
authors.affiliation: Center for Healthcare Outcomes and Policy, University of Michigan, Ann Arbor, MI; Department of Surgery, University of Michigan, Ann Arbor, MI.
authors.forename: Mark R
authors.initials: MR
authors.lastname: Hemmila
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002170:Canada; D004189:Disaster Planning; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D008297:Male; D054527:Mass Casualty Incidents / Q000401:mortality / Q000706:statistics & numerical data*; D008875:Middle Aged; D015233:Models, Statistical; D012042:Registries; D012189:Retrospective Studies; D020379:Risk Adjustment; D018570:Risk Assessment; D055872:Surge Capacity / Q000706:statistics & numerical data*; D014481:United States; D014947:Wounds and Injuries / Q000453:epidemiology* / Q000401:mortality; D055815:Young Adult