Institution and per-surgeon volume versus survival outcome in Pennsylvania's trauma centers

Abstract

Background: The American College of Surgeons recommends minimum patient volumes for trauma centers and surgeons. Those numbers, however, are largely based on results from studies of surgical (but not trauma) relationships between volume and outcome.

Methods: Using stepwise regression, relationships were sought between measures of patient volume per trauma center and per surgeon and ana severity-controlled measure of survival outcome (W). For significant z values, W is the number of additional (or fewer) survivors, per 100 patients treated, than expected from ASCOT norms. W = 0 when z is nonsignificant. Data are from patients admitted in 1988 and 1989 to accredited Pennsylvania trauma centers.

Results: The relationships found for all patients and for adult blunt-injured patients are W = 0.3312 + 0.0200 (NSER/SURG) and W = 0.3638 + 0.0248 (NBSER/SURG), respectively, where NSER/SURG is the number of seriously, injured patients treated annually per surgeon and NBSER/SURG is the number of adult patients with serious blunt injuries treated annually per surgeon. Serious injury was defined, using the Injury Severity Scale, as > = 13 or, using the Abbreviated Injury Scale, as a head injury of > = 3. The relationships explained 36% and 61% of the variance in W (R2 for all patients and adult blunt-injured patients, respectively. To achieve normative survival (W =0), 95% confidence intervals suggest that a trauma surgeon should treat at least 35 seriously injured patients per year and at least 28 adult patients with serious blunt injury annually. No volume-related variable was a significant contributor to predictions of W for adult patients with penetrating injuries or for pediatric patients.

Conclusions: These results support the regionalization of trauma care by affirming that increased per-surgeon experience in the treatment of seriously injured patients is associated with improved outcomes and help define the minimum experience needed to achieve normative survival. Prospective study of the relationship between volume and survival and other outcomes is required.