Inpatient hospital admission and death after outpatient surgery in elderly patients: importance of patient and system characteristics and location of care.
HYPOTHESIS: Surgery at different outpatient care locations in the higher-risk elderly (age >65 years) population is associated with similar rates of inpatient hospital admission and death. DESIGN: Claims analysis of patients undergoing 16 different surgical procedures in a nationally representative (5%) sample of Medicare beneficiaries for the years 1994 through 1999. SETTING: Hospital-based outpatient centers, freestanding ambulatory surgery centers (ASCs), and physicians' office facilities. PATIENTS: Medicare beneficiaries older than 65 years. MAIN OUTCOME MEASURES: Rate of death, emergency department risk, and admission to an inpatient hospital within 7 days of outpatient surgery. RESULTS: We studied 564,267 outpatient surgical procedures: 360,780 at an outpatient hospital, 175,288 at an ASC, and 28,199 at a physician's office. There were no deaths the day of surgery at a physician's office, 4 deaths the day of surgery at an ASC (2.3 per 100,000 outpatient procedures), and 9 deaths the day of surgery at an outpatient hospital (2.5 per 100,000 outpatient procedures). The 7-day mortality rate was 35 per 100,000 outpatient procedures at a physician's office, 25 per 100,000 outpatient procedures at an ASC, and 50 per 100,000 outpatient procedures at an outpatient hospital. The rate of admission to an inpatient hospital within 7 days of outpatient surgery was 9.08 per 1000 outpatient procedures at a physician's office, 8.41 per 1000 outpatient procedures at an ASC, and 21 per 1000 outpatient procedures at an outpatient hospital. In multivariate models, more advanced age, prior inpatient hospital admission within 6 months, surgical performance at a physician's office or outpatient hospital, and invasiveness of surgery identified those patients who were at increased risk of inpatient hospital admission or death within 7 days of surgery at an outpatient facility. CONCLUSION: This study represents an initial effort to demonstrate the risk associated with outpatient surgery in a large, diverse population of elderly individuals.