title: Variation in ambulatory surgery utilization in Michigan.
abstract: BACKGROUND
  The practice of ambulatory surgery has expanded greatly as a result of advances in surgical technology and rising financial pressures. We sought to characterize the utilization of ambulatory surgical practices for common general surgical procedures in Michigan.
  
  
  METHODS
  We identified 33,655 patients within the Michigan Surgery Quality Collaborative clinical registry undergoing general surgical procedures performed on an ambulatory basis between 25% and 75% of the time. Our primary outcome was the incidence of ambulatory surgery. Using multilevel mixed-effects logistic regression models, we adjusted ambulatory surgery utilization rates for patient comorbidities, procedure composition, and hospital characteristics. We then assessed the incidence of postoperative complications across hospitals grouped by their ambulatory surgery utilization rates.
  
  
  RESULTS
  Adjusted utilization rates of ambulatory surgery varied widely across 34 hospitals from 29%-75% (mean = 54%). Risk-adjusted complication rates for ambulatory cases were similar between hospitals performing the least (2.2%) and the most ambulatory surgery (2.3%, P = 0.365). Patient factors and hospital characteristics accounted for 23.3% of the between-hospital variability in ambulatory surgery utilization, whereas most variation was explained by effects at the surgeon level.
  
  
  CONCLUSIONS
  Despite wide variation in ambulatory surgery utilization for general surgical procedures, we were unable to explain observed differences by patient comorbidities, case mix, or hospital characteristics. These data suggest that understanding factors associated with ambulatory surgery utilization may represent a novel avenue for quality improvement within our statewide surgical collaborative.
authors.affiliation: Department of Surgery, University of Michigan, Ann Arbor, Michigan.
authors.forename: Kyle H
authors.initials: KH
authors.lastname: Sheetz
authors.affiliation: Department of Surgery, University of Michigan, Ann Arbor, Michigan.
authors.forename: Lauren
authors.initials: L
authors.lastname: Corona
authors.affiliation: Department of Surgery, University of Michigan, Ann Arbor, Michigan.
authors.forename: Shannon
authors.initials: S
authors.lastname: Cramm
authors.affiliation: Department of Surgery, University of Michigan, Ann Arbor, Michigan.
authors.forename: Allen
authors.initials: A
authors.lastname: Haddad
authors.affiliation: Department of Surgery, University of Michigan, Ann Arbor, Michigan.
authors.forename: Lindsey
authors.initials: L
authors.lastname: Kolar
authors.affiliation: Department of Surgery, University of Michigan, Ann Arbor, Michigan.
authors.forename: Dave
authors.initials: D
authors.lastname: Kozminski
authors.affiliation: Department of Surgery, University of Michigan, Ann Arbor, Michigan.
authors.forename: Ashley
authors.initials: A
authors.lastname: Miller
authors.affiliation: Department of Surgery, University of Michigan, Ann Arbor, Michigan.
authors.forename: Rula
authors.initials: R
authors.lastname: Mualla
authors.affiliation: Department of Surgery, University of Michigan, Ann Arbor, Michigan.
authors.forename: Patrick
authors.initials: P
authors.lastname: Underwood
authors.affiliation: Department of Surgery, University of Michigan, Ann Arbor, Michigan.
authors.forename: Seth A
authors.initials: SA
authors.lastname: Waits
authors.affiliation: Department of Surgery, University of Michigan, Ann Arbor, Michigan.
authors.forename: Greta
authors.initials: G
authors.lastname: Krapohl
authors.affiliation: Department of Surgery, University of Michigan, Ann Arbor, Michigan.
authors.forename: Darrell A
authors.initials: DA
authors.lastname: Campbell
authors.affiliation: Department of Surgery, University of Michigan, Ann Arbor, Michigan. Electronic address: englesbe@med.umich.edu.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Englesbe
mesh_terms: D000368:Aged; D000556:Ambulatory Surgical Procedures / Q000706:statistics & numerical data*; D005260:Female; D013502:General Surgery / Q000706:statistics & numerical data; D006801:Humans; D015994:Incidence; D008297:Male; D008824:Michigan / Q000453:epidemiology; D008875:Middle Aged; D011183:Postoperative Complications / Q000453:epidemiology; D016896:Treatment Outcome