Abstract TMP83: Association Between Hospital Procedural Volumes and Clinical Outcomes For Patients With Non-Traumatic Subarachnoid Hemorrhage

Abstract

Introduction: Previous studies of patients with non-traumatic subarachnoid hemorrhage (SAH) suggest better outcomes at hospitals with higher case and procedural volumes, but the shape of the volume-outcome curve has not been defined. We sought to establish minimum volume criteria for SAH and aneurysm obliteration procedures that could be used for comprehensive stroke centers (CSC) certification. Methods: The 8,512 SAH discharges in the National Inpatient Sample (NIS) from 2010-11 were analyzed. Logistic regression models were used to evaluate the association between clinical outcomes (in-hospital mortality and the NIS-SAH Outcome Measure (NIS-SOM)) and 3 measures of hospital annual case volume (ACV) (nontraumatic SAH discharges, coiling, and clipping procedures). Sensitivity and specificity analyses for the association of desirable clinical outcomes with different volume thresholds were performed. Results: 28.7% of cases underwent clipping and 20.1% underwent coiling with rates of 21.2%for in-hospital mortality and 38.6% for poor outcome on the NIS-SOM. The mean (range) of SAH ACV, coiling ACV, and clipping ACV were 30.9 (1-195), 8.7 (0-94), and 6.1 (0-69). Logistic regression demonstrated improved outcomes with increasing ACVs of SAH discharges and procedures for aneurysm obliteration, with attenuation of the benefit beyond 35 SAH cases/yr. Sensitivity and specificity analyses with different ACV thresholds confirmed the results. Analysis of previously proposed ACV thresholds, including those used as minimum standards for CSC certification, showed that hospitals with more than 35 SAH cases annually had better outcomes compared to hospitals with fewer cases, but some hospitals below this threshold had similar outcomes to those with more cases. The adjusted odds ratio favoring better outcomes with SAH ACV ≥ 35 compared to SAH 20 to 34 was 0.82 for the NIS-SOM (p=0.0054) and 0.80 (p=0.0055) for in-hospital mortality. Conclusions: Outcomes for SAH patients improve with increasing hospital case volumes and procedure volumes, with consistently better outcomes for hospitals with more than 35 SAH cases per year.