Abstract
OBJECTIVES: To assess the impact of ambulatory surgery centers (ASCs) on rates of hospital-based outpatient procedures and adverse events. DATA SOURCES: Twenty percent national sample of Medicare beneficiaries. STUDY DESIGN: A retrospective study of beneficiaries undergoing outpatient surgery between 2001 and 2010. Health care markets were sorted into three groups-those with ASCs, those without ASCs, and those where one opened for the first time. Generalized linear mixed models were used to assess the impact of ASC opening on rates of hospital-based outpatient surgery, perioperative mortality, and hospital admission. PRINCIPAL FINDINGS: Adjusted hospital-based outpatient surgery rates declined by 7 percent, or from 2,333 to 2,163 procedures per 10,000 beneficiaries, in markets where an ASC opened for the first time (p < .001 for test between slopes). Within these markets, procedure use at ASCs outpaced the decline observed in the hospital setting. Perioperative mortality and admission rates remained flat after ASC opening (both p > .4 for test between slopes). CONCLUSIONS: The opening of an ASC in a Hospital Service Area resulted in a decline in hospital-based outpatient surgery without increasing mortality or admission. In markets where facilities opened, procedure growth at ASCs was greater than the decline in outpatient surgery use at their respective hospitals.