Outcomes after cerebral aneurysm clip occlusion in the United States: the need for evidence-based hospital referral

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Object. In an age of multimodality and multidisciplinary treatment of cerebral aneurysms, patient outcomes have improved significantly. For a number of complex surgical procedures, hospitals with high case volumes yield superior outcomes. The effect of hospital volume on the mortality rate after emergency and elective cerebral aneurysm clip occlusion in a nationally representative sample of patients is unknown.

Methods. Using clinical data derived from the Nationwide Inpatient Sample for the years from 1995 through 1999, 12,023 patients who underwent clip occlusion of a cerebral aneurysm (International Classification of Diseases, Ninth Revision, Clinical Modification code 3951) were included. Patient age, comorbid conditions, nature of admission, and diagnosis of subarachnoid hemorrhage were abstracted. Hospital case volume was grouped into quartiles. Unadjusted and case-mix adjusted analyses were performed.

The mean patient age was 53.2 ± 13.5 years. The overall crude postoperative mortality rates for emergency and elective aneurysm clip occlusion were 12.2 and 6.6%, respectively. Very low volume hospitals demonstrated higher mortality rates than very high volume hospitals for both emergency (14.7 compared with 8.9%, p < 0.001) and elective (9.4 compared with 4.5%, p < 0.001) aneurysm surgery. Patient-specific predictors of death in the multivariate model were renal disease (odds ratio [OR] 3.32, p < 0.042); age (> 60 years, OR 2.36, p < 0.001; 51–60 years, OR 1.63, p < 0.001; 40–50 years, OR 1.25, p = 0.047); chronic obstructive pulmonary disease (present, OR 1.52, p < 0.001); and nature of admission (emergency, OR 1.18, p = 0.03). Provider-specific predictors of death included very low volume (OR 1.59, p < 0.001); low-volume (OR 1.37, p = 0.001); and high-volume (OR 1.45, p < 0.001) hospitals compared with very high volume hospitals.

Conclusions. A significant volume—outcome effect exists for surgical treatment of cerebral aneurysms in the US. Factors influencing this effect should be investigated to guide future healthcare policy and evidence-based referral. Whenever possible, healthcare practitioners should refer patients to centers in which superior outcomes are consistently demonstrated.

Article Information

Address reprint requests to: John A. Cowan, Jr., M.D., Department of Neurosurgery, University of Michigan Health System, 1500 East Medical Center Drive, Room 2128 TC, Ann Arbor, Michigan 48109–0338. email: jacowan@umich.edu.

© AANS, except where prohibited by US copyright law.

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    Bar graph showing the postoperative mortality rate for elective and emergency aneurysm clip occlusion based on hospital case volume.

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    Boxplot of annual hospital case volume for surgical management of cerebral aneurysms in the US from 1995 through 1999. Horizontal lines within the boxes represent the mean. Lower areas of the boxes represent the 25th percentile and upper areas of the boxes represent the 75th percentile. Lower and upper intervals represent the 5th and 95th percentiles, respectively.

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