Does volume matter? The effect of trauma surgeons' caseload on mortality

Evidence suggests that trauma centers treating high volumes of severely injured patients produce lower mortality rates than those with low volumes. However, the effect of individual surgeons' trauma caseload on outcomes has not been studied. This study compares outcomes between high-volume (HV) trauma surgeons admitting many patients with high injury severity, and low-volume (LV) surgeons treating fewer critical patients per year.

All trauma patients admitted to a large Level I trauma center over a 12-year period were assigned to either the HV or LV group, depending on the yearly volume of their admitting surgeon. Surgeons treating > 35 severely injured (Injury Severity Score > 15) patients per year were considered HV. Student's t test and chi2 analysis were used to test comparability of LV and HV patient groups and to compare mortality rates. Mortality rates of HV and LV surgeons' patients were compared in six injury patterns selected to represent moderate to severe injury. TRISS methodology (z score) was also used to assess outcomes in the two groups. The inherent bias of the TRISS method in comparing trauma outcomes was minimized by the homogeneity of the studied patient population.

A total of 16,481 patients were admitted to HV surgeons, and 4,214 patients were admitted to LV surgeons. In all subgroups, HV and LV patients were similar regarding age, sex, physiologic status at admission, injury pattern, and injury severity. Mortality rates for HV and LV surgeons were not significantly different between the two groups in any injury pattern. The z score was 1.88 in the HV patient group versus 0.47 in the LV group.

Within a single institution, mortality rates for patients treated by surgeons admitting many severely injured patients were not significantly different from low-volume surgeons' patients, although there was a trend toward higher mortality in the less active surgeons' patients in some subgroups.