title: Impact of ambulatory surgery day of the week on postoperative outcomes: a population-based cohort study.
abstract: OBJECTIVE
  Ambulatory surgery is generally considered safe; however, as many as 3% of patients require unplanned acute postoperative care. The purpose of this study was to measure the impact of the day of the week of surgery on the outcomes of ambulatory surgery.
  
  
  METHODS
  Using population-based health administrative data, we conducted a historical cohort analysis by identifying patients who underwent ambulatory surgery from 2002-2012. Multivariable regression was used to measure the association between the day of the week of surgery and the primary outcomes of 30-day emergency department (ED) visit or hospital readmission after successful discharge on the day of surgery. The secondary outcome that was similarly compared was unsuccessful discharge on the day of surgery.
  
  
  RESULTS
  Of 296,497 patients identified, 32,100 (10.5%) returned to the ED or were readmitted to hospital within 30 days. Adjusting for demographics, comorbidities, and preoperative use of health resources, Friday surgery was most associated with the primary outcome (adjusted hazard ratio, 1.07; 95% confidence interval, 1.03 to 1.11) when compared with Monday surgery. This association was stronger in certain surgery types. There were 9,197 (3.1%) patients who were not discharged on the day of surgery; no association between day of the week and unsuccessful discharge was identified.
  
  
  CONCLUSIONS
  On a population level, there was a small effect of the day of the week of ambulatory surgery on outcomes; however, the clinical impact is likely not relevant. Certain surgical types may be more susceptible to a day of the week effect, but more research is needed to elucidate this notion.
authors.affiliation: Department of Anesthesiology, The Ottawa Hospital, University of Ottawa, 1053 Carling Ave, Room B311, Ottawa, ON, K1Y 4E9, Canada, dmcisaac@toh.on.ca.
authors.forename: Daniel I
authors.initials: DI
authors.lastname: McIsaac
authors.forename: Gregory L
authors.initials: GL
authors.lastname: Bryson
authors.forename: Carl
authors.initials: C
authors.lastname: van Walraven
mesh_terms: D000328:Adult; D000368:Aged; D000556:Ambulatory Surgical Procedures / Q000706:statistics & numerical data*; D015331:Cohort Studies; D015897:Comorbidity; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010351:Patient Discharge; D010359:Patient Readmission; D011153:Population; D011182:Postoperative Care; D011184:Postoperative Period; D012959:Socioeconomic Factors; D016896:Treatment Outcome