Emergency department hospitalization volume and mortality in the United States

Although numerous studies have demonstrated a relationship between higher volume and improved outcomes in the delivery of health services, it has not been extensively explored in the emergency department (ED) setting. Therefore, we seek to examine the association between ED hospitalization volume and mortality for common high-risk conditions.

Using data from the Nationwide Inpatient Sample, a national sample of hospital discharges, we evaluated mortality overall and for 8 different diagnoses between 2005 and 2009 (total admissions 17.55 million). These conditions were chosen because they are frequent (in the top 25 of all ED hospitalizations) and high risk (> 3% observed mortality). EDs were excluded from analysis if they did not have at least 1,000 total annual admissions and 30 disease-specific cases. EDs were then placed into quintiles based on hospitalized volume. Regression techniques were used to describe the relationship between volume (number of hospitalized ED patients per year) and both subsequent early inpatient mortality (within 2 days of admission) and overall mortality, adjusted for patient and hospital characteristics.

Mortality decreased as volume increased overall and for all diagnoses, but the relative importance of volume varied, depending on the condition. Absolute differences in adjusted mortality rates between very high-volume EDs and very low-volume EDs ranged from -5.6% for sepsis (95% confidence interval [CI] -6.5% to -4.7%) to -0.2% for pneumonia (95% CI -0.6% to 0.1%). Overall, this difference was -0.4% (95% CI -0.6% to -0.3%). A similar pattern was observed when early hospital deaths were evaluated.

Patients have a lower likelihood of inhospital death if admitted through high-volume EDs.