Contemporary Analysis of the Volume–Outcome Relationship for Patients With Nontraumatic Subarachnoid Hemorrhage

Abstract

Background Nontraumatic subarachnoid hemorrhage (SAH) carries a substantial mortality burden and risk of long‐term morbidity. Although prior investigations have demonstrated an inverse association between SAH admission volume and in‐hospital mortality, reported thresholds remain broad. Importantly, the relative importance of both admission and procedural volume has yet to be evaluated on a national scale. We examined the association of volume metrics with outcomes in an SAH cohort. Methods All adult (≥18 years) hospitalizations with a primary diagnosis of nontraumatic SAH were identified from the 2016 to 2022 Nationwide Readmissions Database. Multivariable regression models were developed to evaluate the independent and joint associations of SAH admission and clipping and coiling procedural volume with in‐hospital outcomes. Results Of an estimated 142 271 hospitalizations, index mortality was 20.2%. Following risk adjustment, both increasing SAH admission volume and clipping and coiling procedural volume were independently associated with reduced mortality. When modeled jointly, however, clipping and coiling procedural volume remained an independent predictor of mortality (adjusted odds ratio, 0.981 per 10 procedures, P <0.001) whereas SAH admission volume was no longer significant ( P =0.40). Conclusions Joint examination of SAH and clipping and coiling procedural volume revealed procedural caseload to be the dominant predictor of in‐hospital mortality, suggesting that survival benefits historically attributed to admission volume may be more precisely explained by procedural expertise. These findings support reexamination of volume‐based benchmarks in contemporary cerebrovascular care frameworks.