Researchers at the University of California, San Francisco, searched admission records and discharge abstracts for subarachnoid hemorrhage (SAH) in a database of all non-federal hospitals in the state between 1990 and 1999.
Subarachnoid hemorrhage occurs when a blood vessel bursts within the weblike system of vessels and capillaries surrounding the exterior surface of the brain. SAH can cause brain damage, coma and death.
Data on 12,804 patients (62 percent female, average age 52,) admitted to 390 hospital emergency departments for SAH were examined, and outcomes were compared with each facility's annual SAH case rate.
Hospitals were divided into quartiles based on their annual SAH case rate. Those in the lowest quartile had 0-8 cases per year, while hospitals in the highest quartile saw 19-70 cases. Mortality was 49 percent in hospitals with the fewest SAH cases, and 32 percent in those with the most cases.
The correlation between mortality and treatment volume persisted even when the researchers examined multiple variables that might contribute to it. The length of stay was longer for patients at the higher-volume hospitals, and the costs were higher.
In addition, only 4.8 percent of patients at hospitals with the fewest SAH cases each year had been referred to higher-volume centers for care and treatment, the researchers found.
The study mirrors findings for other diseases, note authors Naomi Bardach, B.A., and S. Claiborne Johnston, M.D., Ph.D., assistant professor of neurology and epidemiology. Studies have shown better survival rates at higher-volume facilities for patients with other complex medical needs, including coronary artery bypass surgery, carotid endarterectomy and HIV. Policies discouraging coronary bypass procedures at lower-volume hospitals are credited for sharp declines in patient deaths in New York and Canadian hospitals, the researchers say.
Policies that encourage patient transfer to higher-volume hospitals could have a major impact in reducing mortality from SAH, the researchers conclude, although such transfers are not always feasible. Such policies may be cost-effective, but further confirmation of the benefit of transfer is required.
The study was funded in part by the National Institutes of Health.
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