Hamilton GM, et al. - In this historical cohort study at The Ottawa Hospital, including adults ≥ 18 yr old having elective ambulatory shoulder surgery from January 1, 2011 to December 31, 2016, researchers studied the link between regional anesthesia and postoperative outcomes, including unplanned admissions, Emergency Department visits, readmissions, or death within 30 days of surgery. A total of 1,623 patients met the inclusion criteria, of those, 1,382 (85.2%) patients received peripheral nerve blocks (PNBs). Using one-to-many coarsened exact matching (CEM) to adjust for potential confounders, 211 patients who did not receive a PNB were matched to 950 patients with similar characteristics who did receive a PNB (n = 1,161; 71.5% of total cohort). Findings revealed no significant difference in a composite of adverse postoperative outcomes in association with peripheral nerve blocks in ambulatory shoulder surgery. Results demonstrated lower than expected incidence and moderate effect size associating PNBs with post-discharge events.