The influence of inter-hospital transfers on mortality in severely injured patients.

Purpose: The importance of treating severely injured patients in higher-level trauma centers is undisputable. However, it is uncertain whether severely injured patients that were initially transported to a lower-level trauma center (i.e., undertriage) benefit from being transferred to a higher-level trauma center.

Methods: This observational study included all severely injured patients (i.e., Injury Severity Score ≥ 16) that were initially transported to a lower-level trauma center within eight ambulance regions. The exposure of interest was whether a patient was transferred to a higher-level trauma center. Primary outcomes were 24-h and 30-day mortality. Generalized linear models including inverse probability weights for several potential confounders were constructed to evaluate the association between transfer status and mortality.

Results: We included 165,404 trauma patients that were transported with high priority to a trauma center, of which 3932 patients were severely injured. 1065 (27.1%) patients were transported to a lower-level trauma center of which 322 (30.2%) were transferred to a higher-level trauma center. Transferring undertriaged patients to a higher-level trauma center was significantly associated with reduced 24-h (relative risk [RR] 0.26, 95%-CI 0.10-0.68) and 30-day mortality (RR 0.65, 0.46-0.92). Similar results were observed in patients with critical injuries (24-h: RR 0.35, 0.16-0.77; 30-day: RR 0.55, 0.37-0.80) and patients with traumatic brain injury (24-h: RR 0.31, 0.11-0.83; 30-day: RR 0.66, 0.46-0.96).

Conclusions: A minority of the undertriaged patients are transferred to a higher-level trauma center. An inter-hospital transfer appears to be safe and may improve the survival of severely injured patients initially transported to a lower-level trauma center.