Angiotensin converting enzyme inhibitor (ACEi) or angiotensin receptor blocker (ARB) use prior to major surgery is controversial. We performed a population based retrospective cohort study of 237,208 elderly patients (of whom 101,494 (42.8%) were ACEi or ARB users) who underwent major elective surgery from 1995 to 2010 in Ontario, Canada. The primary outcome was acute kidney injury treated with dialysis (AKI-D) within 14 days following surgery (810 (0.34%) patients). The secondary outcome was all-cause mortality within 90 days following surgery (11,089 (4.67%) patients). After adjusting for potential confounders, preoperative ACEi or ARB use was associated with a lower relative risk of AKI-D (adjusted relative risk (RR): 0.83; 95% confidence interval (CI): 0.71 to 0.98) and a lower relative risk of all-cause mortality (adjusted RR: 0.91; 95% CI: 0.87 to 0.95). Results were consistent in propensity score matched analyses. We observed a significant effect modification by chronic kidney disease on AKI-D (p-value \u3c 0.0001). Randomized controlled trials are needed to clarify this issue
