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

Abstract

ObjectiveThere 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. MethodsThis 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. ResultsThe 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). ConclusionAfter 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.