Severe trauma patient volume was associated with decreased mortality.

BACKGROUND: The relationship between the severe trauma patient volume and outcomes is still being debated. The aim of this study was to evaluate the relationship between severe trauma patient volume, hospital mortality, and door-to-definitive treatment time. METHODS: This was a retrospective cohort study that used recorded data from the Japan Trauma Data Bank. We included severe trauma patients who had an Injury Severity Score greater than 16. Hospitals were categorized according to their annual severe trauma patient volume: low volume, 1-49 (reference), medium volume, 50-99, and high volume, >/= 100]. The association of volume categories with in-hospital mortality was evaluated by use of a mixed-effects model adjusted for patient demographics and trauma severity. Additionally, the association of volume categories with in-hospital mortality among subgroups and with door-to-definitive treatment time were also evaluated. RESULTS: A total of 74,957 severe trauma patients from 213 hospitals were analyzed. In-hospital mortality was 15.7%, 15.2%, and 12.8% in the low volume, medium volume, and high volume groups, respectively. High volume was associated with reduced in-hospital mortality compared to low volume (odds ratio = 0.757, 95% confidence interval = 0.626-0.916). However, medium volume was not associated with reduced in-hospital mortality. Among subgroups, high volume was associated with reduced in-hospital mortality only in the probability of survival >/= 0.5. Door-to-definitive treatment time was decreased in high volume, however, high volume was not associated with reduced in-hospital mortality among the patients who underwent definitive treatment and the patients whose ps < 0.5. CONCLUSIONS: Severe trauma patient volume was associated with decreased mortality by decreasing preventable trauma death.