Relationship Between Provider Volume and Mortality for Carotid Endarterectomies in New York State

Abstract

Background and Purpose —The objective of this study was to assess the relationship between each of 2 provider volume measures for carotid endarterectomies (CEs) (annual hospital volume and annual surgeon volume) and in-hospital mortality. New York’s Statewide Planning and Research (SPARCS) administrative database was used to identify all 28 207 patients for whom carotid endarterectomy was the principal procedure performed in New York State hospitals between January 1, 1990, and December 31, 1995. Methods —A statistical model was developed to predict in-hospital mortality using age, admission status, and several conditions found to be associated with higher-than-average mortality. This model was then used to calculate risk-adjusted mortality rates for various intersections of hospital and surgeon volume ranges. Results —Risk-adjusted in-hospital mortality ranged from 1.96% (95%confidence interval, 1.47 to 2.57) for patients having surgeons with annual CE volumes of <5 in hospitals with annual CE volumes of ≤100 to 0.94% (95% confidence interval, 0.73 to 1.19) for patients having surgeons with annual volumes of ≥5 in hospitals with annual CE volumes of >100. These 2 rates were statistically different. Conclusions —We conclude that the in-hospital mortality rates for carotid endarterectomies performed by surgeons with extremely low annual volumes (<5) and for hospitals with low volumes (≤100) are significantly higher than the in-hospital rates of higher-volume surgeons and hospitals, even after taking preprocedural patient severity of illness into account.