Neither Diabetes nor Glucose-Lowering Drugs Are Associated With Mortality After Noncardiac Surgery in Patients With Coronary Artery Disease or Heart Failure

Background: It is unclear whether diabetes mellitus or use of particular glucose-lowering agents is associated with increased risk of mortality after noncardiac surgery in patients with known cardiac disease. Methods: We carried out a retrospective cohort study using 4 linked administrative databases in the province of Alberta, Canada from 1999-2006. Results: Of the 32,834 patients with known cardiac disease in our cohort, 9305 (28%) had diabetes. All-cause 30-day mortality after noncardiac surgery was 6.4% in patients with diabetes, and 6.1% in those without diabetes (multivariate adjusted odds ratio [aOR] 0.97, 95% confidence interval [CI], 0.87-1.08). In the 24,037 patients older than 65, mortality was 7.5% in individuals with diabetes and 7.5% in those without diabetes (5.7% in those taking insulin [aOR, 0.89; 95% CI, 0.70-1.13], 8.0% in those using oral agents only [aOR, 1.08; 95% CI, 0.95-1.22]). None of the glucose-lowering drug classes were associated with perioperative mortality in elderly cardiac patients (sulfonylureas aOR, 0.94; 95% CI, 0.76-1.16; metformin aOR, 0.92; 95% CI, 0.74-1.14; thiazolidinediones aOR, 0.64; 95% CI, 0.40-1.04; insulin aOR, 0.83; 95% CI, 0.65-1.08), but use of angiotensin-converting enzyme inhibitors/angiotensin receptor blockers (aOR, 0.83; 95% CI, 0.75-0.93), beta-blockers (aOR, 0.82; 95% CI, 0.72-0.93), or statins (aOR, 0.65; 95% CI, 0.55-0.78) in the 100 days before surgery were associated with lower 30-day mortality. Conclusions: Neither diabetes nor exposure to common classes of glucose-lowering drugs preoperatively were associated with increased perioperative mortality in cardiac patients undergoing noncardiac surgery. However, cardiac patients not using angiotensin-converting enzyme inhibitors/angiotensin receptor blockers, beta-blockers, or statins preoperatively exhibited higher mortality rates, emphasizing the importance of optimizing evidence-based therapy before elective surgery in these patients.