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Impact of Volume Change Over Time on Trauma Mortality in the United States

Brown, Joshua B. MD, MSc*; Rosengart, Matthew R. MD, MPH*,†; Kahn, Jeremy M. MD, MS; Mohan, Deepika MD, MPH*,†; Zuckerbraun, Brian S. MD*; Billiar, Timothy R. MD*; Peitzman, Andrew B. MD*; Angus, Derek C. MD, MPH; Sperry, Jason L. MD, MPH*,†

doi: 10.1097/SLA.0000000000001838
ORIGINAL ARTICLES
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Objective: To evaluate the association of trauma center volume change over time with mortality.

Background: Regionalization of trauma systems assumes a volumeoutcome relationship for severe injury. Whereas this has been shown for cross-sectional volume, it is unclear whether volume changes over time translate into predictable outcome changes.

Methods: Retrospective cohort study of severely injured (injury severity score >15) patients from the National Trauma Databank 2000 to 2012. A center-level standardized mortality ratio (SMR) was constructed (ratio of observed to expected deaths). Expected mortality was obtained from multilevel logistic regression model, adjusting for demographics, mechanism, vital signs, and injury severity. Center-level percent volume change was assessed across early (2000–2006) and late (2007–2012) periods. Longitudinal panel modeling evaluated association between annual SMR change and volume change over preceding years.

Results: There were 839,809 patients included from 287 centers. Each 1% increase in volume was associated with 73% increased odds of improving SMR over time [odds ratio (OR) 1.73; 95% confidence interval (CI) 1.03–2.91; P = 0.03]. Each 1% decrease in volume was associated with 2-fold increase in odds of worsening SMR over time (OR 2.14; 95% CI 1.07–4.26, P = 0.03). Significant improvement in the SMR emerged after 3 or more preceding years of increasing volume (SMR change −0.008; 95% CI −0.015, −0.002; P = 0.01). This benefit occurred only in centers that were level I or II verified.

Conclusions: Increasing volume was associated with improving outcomes, whereas decreasing volume was associated with worsening outcomes. High-level trauma center infrastructure seems to facilitate the volumeoutcome relationship. The trauma center designation process should consider volume changes in the overall system.

*Division of Trauma and General Surgery, Department of Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA

Department of Critical Care Medicine, University of Pittsburgh Medical Center, Pittsburgh, PA.

Reprints: Jason L. Sperry, MD, MPH, Division of Trauma and General Surgery, Department of Surgery, University of Pittsburgh Medical Center, 200 Lothrop Street, Pittsburgh, PA 15213. E-mail: sperryjl@upmc.edu.

Author contributions: Dr Brown had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Study concept: Brown, Rosengart, and Sperry; study design: Brown, Rosengart, Kahn, Mohan, and Sperry; acquisition of data: Brown and Sperry; analysis of data: Brown; interpretation of data: Brown, Rosengart, Kahn, Mohan, Zuckerbraun, Billiar, Peitzman, Angus, and Sperry; drafting of the manuscript: Brown and Sperry; critical revision of the manuscript for important intellectual content: Brown, Rosengart, Kahn, Mohan, Zuckerbraun, Billiar, Peitzman, Angus, and Sperry; statistical data analysis/design: Brown, Rosengart, Kahn, and Sperry; administrative, technical, or material support: Brown, Rosengart, Kahn, Mohan, Zuckerbraun, Billiar, Angus, and Sperry; supervision: Rosengart, Billiar, Peitzman, Angus, and Sperry; approved current version of manuscript of publication in its current form: Brown, Rosengart, Kahn, Mohan, Zuckerbraun, Billiar, Peitzman, Angus, and Sperry.

Funding/support: No funding or support was directly received to perform the current study.

Disclosure: Dr Brown receives support from an institutional T-32 Ruth L. Kischstein National Research Service Award training grant (5T32GM008516) from the National Institutes of Health. The authors report no conflicts of interest.

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