Impact of hospital case-volume on subarachnoid hemorrhage outcomes: A nationwide analysis adjusting for hemorrhage severity.

OBJECTIVE: There have been suggestions that patients with subarachnoid hemorrhage (SAH) have a better outcome when treated in high-volume centers. Much of the published literature on the subject is limited by an inability to control for severity of SAH. METHODS: This is a nationwide retrospective cohort analysis using the Nationwide Inpatient Sample (NIS). The NIS Subarachnoid Severity Scale was used to adjust for severity of SAH in multivariate logistic regression modeling. RESULTS: The records of 47 911 414 hospital admissions from the 2006-2011 NIS samples were examined. There were 11 607 patients who met inclusion criteria for the study. Of these, 7787 (67.0%) were treated at a high-volume center compared with 3820 (32.9%) treated at a low-volume center. Patients treated at high-volume centers compared with low-volume centers were more likely to receive endovascular aneurysm control (58.5% vs 51.2%, P=.04), be transferred from another hospital (35.4% vs 19.7%, P<.01), be treated in a teaching facility (97.3% vs 72.9%, P<.01), and have a longer length of stay (14.9 days [interquartile range 10.3-21.7] vs 13.9 days [interquartile range, 8.9-20.1], P<.01). After adjustment for all baseline covariates, including severity of SAH, treatment in a high-volume center was associated with an odds ratio for death of 0.82 (95% confidence interval, 0.72-0.95; P<.01) and a higher odds of a good functional outcome (odds ratio, 1.16; 95% confidence interval, 1.04-1.28; P<.01). CONCLUSION: After adjustment for severity of SAH, treatment in a high-volume center was associated with a lower risk of in-hospital mortality and a higher odds of a good functional outcome.