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.

Conclusion: 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.

Figure 1

Outcome trends by time. Proportion of all SAH cases resulting in inpatient mortality (red line), bad outcomes (orange line), or good outcomes/discharge to home (green line) dichotomized by year. Vertical lines represent 95% confidence intervals.

Figure 2

Volume-outcome associations. Each row of panels demonstrates volume-outcome associations for each of the 3 outcome studies (inpatient mortality, bad outcomes, and good outcomes/discharge to home. The left-hand column of panels demonstrates the volume-outcome association after adjusting for the temporal trend only, and the right-hand column shows the fully adjusted association—age, sex, race/ethnicity (including a missing indicator for states that do not report race/ethnicity data), year of admission, transfer status (whether a patient was transferred from another hospital), insurance, all individual Charlson comorbidities, intubation status, and APR-DRG mortality category. A) Time-adjusted mortality. B) Fully adjusted mortality. C) Time-adjusted bad outcomes. D) Fully adjusted bad-outcomes. E) Time-adjusted good outcomes/discharge to home. F) Fully adjusted good outcomes/discharge to home.