Hospital case-volume is associated with case-fatality after aneurysmal subarachnoid hemorrhage

Background: Inverse association between hospital case-volume and case-fatality has been observed for various nonsurgical interventions and surgical procedures. Aims: To study the impact of hospital case-volume on outcome after aneurysmal subarachnoid hemorrhage (aSAH). Methods: We included aSAH patients who underwent aneurysm coiling or clipping from tertiary care medical centers across three continents using the Dr Foster Stroke GOAL database 2007–2014. Hospitals were categorized by annual case-volume (low volume: <41/year; intermediate: 41–70/year; high: >70/year). Primary outcome was 14-day in-hospital case-fatality. We calculated proportions, and used multiple logistic regression to adjust for age, sex, differences in comorbidity or disease severity, aneurysm treatment modality, and hospital. Results: We included 8525 patients (2363 treated in low volume hospitals, 3563 treated in intermediate volume hospitals, and 2599 in high-volume hospitals). Crude 14-day case-fatality for hospitals with low case-volume was 10.4% (95% confidence interval (CI) 9.2–11.7%), for intermediate volume 7.0% (95% CI 6.2–7.9%; adjusted odds ratio (OR) 0.63 (95%CI 0.47–0.85)) and for high volume 5.4% (95% CI 4.6–6.3%; adjusted OR 0.50 (95% CI 0.33–0.74)). In patients with clipped aneurysms, adjusted OR for 14-day case-fatality was 0.46 (95% CI 0.30–0.71) for hospitals with intermediate case-volume and 0.42 (95% CI 0.25–0.72) with high case-volume. In patients with coiled aneurysms, adjusted OR was 0.77 (95% CI 0.55–1.07) for hospitals with intermediate case-volume and 0.56 (95% CI 0.36–0.87) with high case-volume. Conclusions: Even within a subset of large, tertiary care centers, intermediate and high hospital case-volume is associated with lower case-fatality after aSAH regardless of treatment modality, supporting centralization to higher volume centers.