Abstract 3954: Does the Volume of Stroke/TIA Admissions Relate to Clinical Outcomes in the Ontario Stroke System?

Abstract

Background: Previous research has found decreased mortality rates among hospitals that treat high volumes of patients for specific surgical and medical conditions. The degree of association between mortality and volume varies substantially by condition and procedure, and while this relationship has been examined for many surgical procedures and medical conditions, few studies have looked at stroke We examine the volume-outcome relationship among Ischemic stroke patients. Knowledge of how to guide access to care for people with stroke is of increasingly concern given expected growing costs of medical care. Methods: All ischemic stroke separations at 128 acute hospitals in the province of Ontario from 2003 to 2009 were analyzed using administrative databases. Spline plots were used to establish small, medium and high volume-based categories. Mulivariate hierarchical modeling was used to evaluate the volume outcome relationship. The outcome of interest was 30-day mortality. Results: From 2003 through 2009, 71,856 hospitalizations for stroke/TIA occurred in 128 hospitals. The mean (+/- SD) number of annual hospitalizations for stroke/TIA was 43(30) for small volume hospitals, 157(55) for medium volume hospitals and 278(73) for high volume hospitals. Patient Characteristics: Patients admitted to high volume hospitals were younger, 54% of patients are 75 years of age or older compared to 61% at small volume hospitals (p <0.0001). Patients at small volume hospitals were similar with respect to prevalence of comordid conditions with exception of hypertension, cancer, diabetes, old AMI and renal disease where patients at small volume hospitals had lower prevalence (p < 0.01). Hospital Characteristics: Approximately 15% were specialized stroke centres and 7% had the capacity to provide neurosurgical services. Large volume hospitals were more likely to be specialized stroke centres and or teaching hospitals compared to medium or small hospitals. Overall 30-day risk-adjusted ischemic stroke mortality over the seven year period was 17%. Patients cared for in low volume hospitals have a 30% higher mortality rate compared to patients cared for in a high volume hospital. There was no statistically significant difference in 30-day mortality between medium and high volume hospitals. Conclusions: Similar to procedure-based volume outcome relationships, there does appear to be an association between acute hospital stroke volume and 30-day mortality among ischemic stroke patients in Ontario. Hospitals that have average annual stroke volumes greater than 15 but less than 45 per year have 30 day mortality rates 30% higher than hospitals that see on average 278 stroke/TIA patients per year.itals. The critical threshold is about 150 patients per year. This could be explained by higher likelihood of admission to stroke units or to the expertise developed by regularly caring for stroke patients.