Association between ambulance station case volume and clinical outcomes in moderate to severe trauma.

Objectives: The effect of the case volume of emergency medical services (EMS) on the clinical outcomes of trauma is uncertain. The purpose of this study was to evaluate the association between the case volume of an ambulance station and clinical outcomes in moderate to severe trauma patients. Methods: Adult trauma patients with injury severity scores greater than 8 who were transported by the EMS between 2018 and 2019 were analyzed. The main exposure was the annual case volume of moderate to severe trauma at the ambulance station where the patient-transporting ambulance was based: low-volume (less than 60 cases), intermediate-volume (between 60 and 89 cases), and high-volume (equal or greater than 90 cases). The primary outcome was in-hospital mortality. Multilevel multivariable logistic regression analysis was conducted to calculate adjusted odds ratios (AORs) and 95% confidence intervals (CIs), with the high-volume group used as the reference. Results: In total, 21,498 trauma patients were analyzed. The high-volume group exhibited lower in-hospital mortality, 447 (9.0%), compared to 867 (14.1%) in the intermediate-volume group and 1,458 (14.1%) in the low-volume group. There was a significantly higher odds of in-hospital mortality: low-volume group (AOR 95% CI: 1.20 (0.95-1.51)) and intermediate-volume group (AOR 95% CI: 1.29 (1.02-1.64)) when compared to the high-volume group. Conclusions: The case volume at an ambulance station is associated with in-hospital mortality in patients with moderate to severe trauma. These results should be considered when constructing an EMS system and education program for prehospital trauma care.