title: Trends in hospital volume and operative mortality for high-risk surgery.
abstract: BACKGROUND
  There were numerous efforts in the United States during the previous decade to concentrate selected surgical procedures in high-volume hospitals. It remains unknown whether referral patterns for high-risk surgery have changed as a result and how operative mortality has been affected.
  
  
  METHODS
  We used national Medicare data to study patients undergoing one of eight different cancer and cardiovascular operations from 1999 through 2008. For each procedure, we examined trends in hospital volume and market concentration, defined as the proportion of Medicare patients undergoing surgery in the top decile of hospitals by volume per year. We used regression-based techniques to assess the effects of volume and market concentration on mortality over time, adjusting for case mix.
  
  
  RESULTS
  Median hospital volumes of four cancer resections (lung, esophagus, pancreas, and bladder) and of repair of abdominal aortic aneurysm (AAA) rose substantially. Depending on the procedure, higher hospital volumes were attributable to an increasing number of cases nationwide, an increasing market concentration, or both. Hospital volumes rose slightly for aortic-valve replacement but fell for coronary-artery bypass grafting and carotid endarterectomy. Operative mortality declined for all eight procedures, ranging from a relative decline of 8% for carotid endarterectomy (1.3% mortality in 1999 and 1.2% in 2008) to 36% for AAA repair (4.4% in 1999 and 2.8% in 2008). Higher hospital volumes explained a large portion of the decline in mortality for pancreatectomy (67% of the decline), cystectomy (37%), and esophagectomy (32%), but not for the other procedures.
  
  
  CONCLUSIONS
  Operative mortality with high-risk surgery fell substantially during the previous decade. Although increased market concentration and hospital volume have contributed to declining mortality with some high-risk cancer operations, declines in mortality with other procedures are largely attributable to other factors. (Funded by the National Institute on Aging.).
authors.affiliation: Center for Healthcare Outcomes and Policy and the Section of General Surgery, Department of Surgery, University of Michigan, Ann Arbor, USA. jfinks@umich.edu
authors.forename: Jonathan F
authors.initials: JF
authors.lastname: Finks
authors.forename: Nicholas H
authors.initials: NH
authors.lastname: Osborne
authors.forename: John D
authors.initials: JD
authors.lastname: Birkmeyer
mesh_terms: D000368:Aged; D013504:Cardiovascular Surgical Procedures / Q000401:mortality* / Q000639:trends; D016009:Chi-Square Distribution; D017052:Hospital Mortality / Q000639:trends*; D006761:Hospitals / Q000706:statistics & numerical data* / Q000639:trends; D006801:Humans; D006278:Medicare; D009369:Neoplasms / Q000401:mortality / Q000601:surgery*; D020379:Risk Adjustment; D013514:Surgical Procedures, Operative / Q000401:mortality* / Q000639:trends; D014481:United States