Relationship between the volume of craniotomies for cerebral aneurysm performed at New York State hospitals and in-hospital mortality

Background and Purpose After a craniotomy for cerebral aneurysm, postoperative mortality can be significant. Previous studies have shown that hospitals performing frequent high-risk procedures (such as coronary artery bypass) have a lower mortality than hospitals where these procedures are performed infrequently. Methods The Statewide Planning and Research Cooperative System of the New York State Department of Health reviewed all discharges in New York State from 1987 through 1993 for the diagnoses of subarachnoid hemorrhage and/or cerebral aneurysm and for patients with the procedure code for craniotomy for ruptured or unruptured cerebral aneurysm. In-hospital mortality and length of stay were examined in relation to the volume of craniotomies for aneurysm performed at each individual hospital. Results A total of 15 376 discharges for subarachnoid hemorrhage and 5638 craniotomies for aneurysm were tabulated in 208 hospitals. For all patients who underwent craniotomy for ruptured cerebral aneurysm (n=4034), there was a 43% (95% confidence interval, 29% to 57%) reduction in mortality rate in hospitals performing more than 30 craniotomies per year for cerebral aneurysm compared with hospitals performing less surgery (8.8% versus 15.5%, P<.0001). For all patients who underwent craniotomy for unruptured cerebral aneurysm (n=1604), there was an identical 43% (95% confidence interval, 14% to 73%) reduction in mortality in hospitals performing more than 30 craniotomies per year for cerebral aneurysm (4.6% versus 8.1%, P=.0087). Conclusions Hospitals that frequently perform aneurysm operations have lower mortality rates for patients undergoing craniotomy for cerebral aneurysm than hospitals that perform fewer operations.