The Relationship between Hospital Volume and Mortality in Severe Sepsis

Rationale: Severe sepsis is increasing in incidence and has a high rate of inpatient mortality. Hospitals that treat a larger number of patients with severe sepsis may offer a survival advantage. Objectives: We sought to assess the effect of severe sepsis case volume on mortality, hypothesizing that higher volume centers would have lower rates of inpatient death. Methods: We performed a retrospective cohort study over a 7-year period (2004-2010), using a nationally representative sample of hospital admissions, examining the relation between volume, urban location, organ dysfunction, and survival. Measurements and Main Results: To identify potential differences in outcomes, hospitals were divided into five categories (<50, 50-99, 100-249, 250-499, and 500+ annual cases) and adjusted mortality was compared by volume. A total of 914,200 patients with severe sepsis were identified over a 7-year period (2004-2010). Overall in-hospital mortality was 28.1%. In a fully adjusted model, there was an inverse relationship between severe sepsis case volume and inpatient mortality. Hospitals in the highest volume category had substantially improved survival compared with hospitals with the lowest case volume (adjusted odds ratio, 0.64; 95% confidence interval, 0.60-0.69). In cases of severe sepsis with one reported organ dysfunction, a mortality of 18.9% was found in hospitals with fewer than 50 annual cases compared with 10.4% in hospitals treating 500+ cases (adjusted odds ratio, 0.54; 95% confidence interval, 0.49-0.59). Similar differences were found in patients with up to three total organ dysfunctions. Conclusions: Patients with severe sepsis treated in hospitals with higher case volumes had improved adjusted outcomes.