title: High Subarachnoid Hemorrhage Patient Volume Associated With Lower Mortality and Better Outcomes.
abstract: BACKGROUND
  High-volume centers have better outcomes than low-volume centers when managing complex conditions including subarachnoid hemorrhage (SAH).
  
  
  OBJECTIVE
  To quantify SAH volume-outcome association and determine the extent to which this association is influenced by aggressiveness of care.
  
  
  METHODS
  A serial cross-sectional retrospective study using the Nationwide Inpatient Sample for 2002 to 2010 was performed. Included were all adult (older than 18 years of age) discharged patients with a primary diagnosis of SAH admitted from the emergency department or transferred to a discharging hospital; cases of trauma or arteriovenous malformation were excluded. Survey-weighted descriptive statistics estimated temporal trends. Multilevel logistic regression estimated volume-outcome associations for inpatient mortality and discharge home. Models were adjusted for demographic characteristics, year, transfer status, insurance status, all individual Charlson comorbidities, intubation, and all patient-refined, diagnosis-related group mortality. Analyses were repeated, excluding cases in which aggressive care was not pursued.
  
  
  RESULTS
  A total of 32,336 discharges were included; 13,398 patients underwent clipping (59.1%) or coiling (40.9%). The inpatient mortality rate decreased from 32.2% in 2002 to 22.2% in 2010; discharge home increased from 28.5% to 40.8% during the same period. As SAH volume decreased from 100/year, the mortality rate increased from 18.7% to 19.8% at 80/year, 21.7% at 60/year, 24.5% at 40/year, and 28.4% at 20/year. As SAH patient volume decreased, the probability of discharge home decreased from 40.3% at 100/year to 38.7% at 60/year, and 35.3% at 20/year. Better outcomes persisted in patients receiving aggressive care and in those not receiving aggressive care.
  
  
  CONCLUSIONS
  Short-term SAH outcomes have improved. High-volume hospitals have more favorable outcomes than low-volume hospitals. This effect is substantial, even for hospitals conventionally classified as high volume.
authors.affiliation: Departments of *Neurosurgery, ‡Radiology, and §Neurology, University of Michigan, Ann Arbor, Michigan.
authors.forename: Aditya S
authors.initials: AS
authors.lastname: Pandey
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Gemmete
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Wilson
authors.forename: Neeraj
authors.initials: N
authors.lastname: Chaudhary
authors.forename: B Gregory
authors.initials: BG
authors.lastname: Thompson
authors.forename: Lewis B
authors.initials: LB
authors.lastname: Morgenstern
authors.forename: James F
authors.initials: JF
authors.lastname: Burke
mesh_terms: D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D017052:Hospital Mortality / Q000639:trends*; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D007297:Inpatients; D008297:Male; D008875:Middle Aged; D010351:Patient Discharge / Q000706:statistics & numerical data; D012189:Retrospective Studies; D013345:Subarachnoid Hemorrhage / Q000401:mortality*