Assessing the Ambulatory Surgery Center Volume-Outcome Association

In surgical patients, it is well known that higher hospital procedure volume is associated with better outcomes. To our knowledge, this volume-outcome association has not been studied in ambulatory surgery centers (ASCs) in the US.

To determine if low-volume ASCs have a higher rate of revisits after surgery, particularly among patients with multimorbidity.

This matched case-control study used Medicare claims data and analyzed surgeries performed during 2018 and 2019 at ASCs. The study examined 2328 ASCs performing common ambulatory procedures and analyzed 4751 patients with a revisit within 7 days of surgery (defined to be either 1 of 4735 revisits or 1 of 16 deaths without a revisit). These cases were each closely matched to 5 control patients without revisits (23 755 controls). Data were analyzed from January 1, 2018, through December 31, 2019.

Seven-day revisit in patients (cases) compared with the matched patients without the outcome (controls) in ASCs with low volume (less than 50 procedures over 2 years) vs higher volume (50 or more procedures).

Patients at a low-volume ASC had a higher odds of a 7-day revisit vs patients who had their surgery at a higher-volume ASC (odds ratio [OR], 1.21; 95% CI, 1.09-1.36; P = .001). The odds of revisit for patients with multimorbidity were higher at low-volume ASCs when compared with higher-volume ASCs (OR, 1.57; 95% CI, 1.27-1.94; P < .001). Among patients with multimorbidity in low-volume ASCs, for those who underwent orthopedic procedures, the odds of revisit were 84% higher (OR, 1.84; 95% CI, 1.36-2.50; P < .001) vs higher-volume centers, and for those who underwent general surgery or other procedures, the odds of revisit were 36% higher (OR, 1.36; 95% CI, 1.01-1.83; P = .05) vs a higher-volume center. The findings were not statistically significant for patients without multimorbidity.

In this observational study, the surgical volume of an ASC was an important indicator of patient outcomes. Older patients with multimorbidity should discuss with their surgeon the optimal location of their care.