title: Mortality benefit of transfer to level I versus level II trauma centers for head-injured patients.
abstract: OBJECTIVE
  To determine whether head-injured patients transferred to level I trauma centers have reduced mortality relative to transfers to level II trauma centers.
  
  
  METHODS
  Retrospective cohort study of 542 patients with head injury who initially presented to 1 of 31 rural trauma centers in Oregon and Washington, and were transferred from the emergency department to 1 of 15 level I or level II trauma centers, between 1991 and 1994.
  
  
  METHODS
  A bivariate probit, instrumental variables model was used to estimate the effect of transfer to level I versus level II trauma centers on 30-day postdischarge mortality. Independent variables included age, gender, Injury Severity Scale (ISS), other indicators of injury severity, and a dichotomous variable indicating transfer to a level I trauma center. The differential distance between the nearest level I and level II trauma centers was used as an instrument.
  
  
  RESULTS
  Patients transferred to level I trauma centers differ in unmeasured ways from patients transferred to level II trauma centers, biasing estimates based on standard statistical methods. Transfer to a level I trauma center reduced absolute mortality risk by 10.1% (95% confidence interval 0.3%, 22.2%) compared with transfer to level II trauma centers.
  
  
  CONCLUSIONS
  Patients with severe head injuries transferred from rural trauma centers to level I centers are likely to have improved survival relative to transfer to level II centers.
authors.affiliation: Center for Policy and Research in Emergency Medicine, Department of Emergency Medicine, Oregon Health and Science University, Portland, OR, USA.
authors.forename: K John
authors.initials: KJ
authors.lastname: McConnell
authors.forename: Craig D
authors.initials: CD
authors.lastname: Newgard
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Mullins
authors.forename: Melanie
authors.initials: M
authors.lastname: Arthur
authors.forename: Jerris R
authors.initials: JR
authors.lastname: Hedges
mesh_terms: D002391:Catchment Area, Health; D015331:Cohort Studies; D016001:Confidence Intervals; D006259:Craniocerebral Trauma / Q000145:classification / Q000401:mortality* / Q000534:rehabilitation; D004636:Emergency Service, Hospital; D006780:Hospitals, Rural / Q000592:standards / Q000706:statistics & numerical data; D006786:Hospitals, Urban / Q000592:standards / Q000706:statistics & numerical data; D006801:Humans; D015601:Injury Severity Score; D009922:Oregon / Q000453:epidemiology; D010360:Patient Transfer / Q000706:statistics & numerical data*; D012189:Retrospective Studies; D016019:Survival Analysis; D014187:Transportation of Patients / Q000706:statistics & numerical data; D014193:Trauma Centers / Q000145:classification* / Q000706:statistics & numerical data*; D014861:Washington / Q000453:epidemiology