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Impact of ambulatory surgery day of the week on postoperative outcomes: a population-based cohort study


Purpose — 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.

Conclusion — 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.



McIsaac DI, Bryson GL, van Walraven C. Can J Anaesth. 2015; 62(8):857-65. Epub 2015 May 27.

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