Association between subarachnoid hemorrhage outcomes and number of cases treated at California hospitals.

BACKGROUND AND PURPOSE Studies of several complex medical conditions have shown that outcomes are better at hospitals that treat more cases. We tested the hypothesis that patients with subarachnoid hemorrhage treated at high-volume hospitals have better outcomes. METHODS Using a database of all admissions to nonfederal hospitals in California from 1990 to 1999, we obtained discharge abstracts for patients with a primary diagnosis of subarachnoid hemorrhage who were admitted through the emergency department. Hospital volume, defined as the average number of subarachnoid hemorrhage cases admitted each year, was divided into quartiles. Rates of mortality, adverse outcomes (death or discharge to long-term care), length of stay, and hospital charges were computed by univariate analysis and by multivariable general estimating equations, with adjustment for demographic and admission characteristics. RESULTS A total of 12 804 patients were admitted for subarachnoid hemorrhage through the emergency departments of 390 hospitals. Hospital volumes varied from 0 to 8 cases per year in the first quartile to 19 to 70 cases per year in the fourth quartile. The mortality rate in the lowest volume quartile (49%) was larger than that in the highest volume quartile (32%, P<0.001). In multivariable analysis, the difference persisted (odds ratio comparing highest with lowest volume quartiles 0.57, 95% CI 0.48 to 0.67; P<0.001). At higher volume hospitals, lengths of stay were longer, and hospital charges were greater in univariate and multivariable models (all P<0.001). Only 4.8% of those admitted to hospitals in the lowest volume quartile were transferred to hospitals in the highest quartile. CONCLUSIONS In this study of discharge abstracts in California, hospitals that treated more cases of subarachnoid hemorrhage had substantially lower rates of in-hospital mortality. Few patients with subarachnoid hemorrhage are being transferred to high-volume centers.