Volume 40 | Number 2 | April 2005

Abstract List

K. John McConnell Ph.D., Craig D. Newgard, Richard J. Mullins, Melanie Arthur, Jerris R. Hedges


To determine whether head‐injured patients transferred to level I trauma centers have reduced mortality relative to transfers to level II trauma centers.

Data Source/Study Setting

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.

Study Design

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.

Principal Findings

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.


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.