title: Emergency department hospitalization volume and mortality in the United States.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  Patients have a lower likelihood of inhospital death if admitted through high-volume EDs.
authors.affiliation: Department of Emergency Medicine, University of Michigan, Ann Arbor, MI; Center for Healthcare Outcomes and Policy, University of Michigan, Ann Arbor, MI; Institute for Healthcare Policy and Innovation, University of Michigan, Ann Arbor, MI. Electronic address: kkocher@umich.edu.
authors.forename: Keith E
authors.initials: KE
authors.lastname: Kocher
authors.affiliation: Department of Emergency Medicine, University of Michigan, Ann Arbor, MI; Institute for Healthcare Policy and Innovation, University of Michigan, Ann Arbor, MI; Michigan Center for Integrative Research in Critical Care, University of Michigan, Ann Arbor, MI.
authors.forename: Adrianne N
authors.initials: AN
authors.lastname: Haggins
authors.affiliation: Department of Emergency Medicine, University of Michigan, Ann Arbor, MI.
authors.forename: Amber K
authors.initials: AK
authors.lastname: Sabbatini
authors.affiliation: Department of Emergency Medicine, University of Michigan, Ann Arbor, MI; Robert Wood Johnson Foundation Clinical Scholars Program, University of Michigan, Ann Arbor, MI; VA Center for Clinical Management Research, VA Ann Arbor Healthcare System, Ann Arbor, MI.
authors.forename: Kori
authors.initials: K
authors.lastname: Sauser
authors.affiliation: Los Angeles Medical Center Emergency Medicine, Los Angeles, CA; Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, CA.
authors.forename: Adam L
authors.initials: AL
authors.lastname: Sharp
mesh_terms: D000368:Aged; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D005260:Female; D006471:Gastrointestinal Hemorrhage / Q000401:mortality; D006333:Heart Failure / Q000401:mortality; D017052:Hospital Mortality; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000401:mortality; D011014:Pneumonia / Q000401:mortality; D051437:Renal Insufficiency / Q000401:mortality; D012131:Respiratory Insufficiency / Q000401:mortality; D018805:Sepsis / Q000401:mortality; D020521:Stroke / Q000401:mortality; D014481:United States / Q000453:epidemiology