Renin-angiotensin system blockers and 1-year mortality in patients with post-operative acute kidney injury

Background Angiotensin-converting enzyme inhibitor (ACE-I) and angiotensin-receptor blocker (ARB) users may be associated with increased mortality in patients with post-operative acute kidney injury (AKI), but data are limited. We studied whether users of ACE-I/ARBs with AKI after colorectal cancer surgery (CRC) were associated with increased 1-year mortality after AKI. Methods This population-based cohort study in Northern Denmark included patients with AKI within 7 days after CRC surgery during 2005-2014. From reimbursed prescriptions, patients were classified as ACE-I/ARB current, former, or non-users. We computed the cumulative 30-day and 1-year mortality after AKI with 95% confidence intervals (95% CI) using the Kaplan-Meier method (1-survival function). Hazard ratios (HRs) comparing mortality in current and former users with non-users were computed by Cox proportional hazards regression analyses, controlling for potential confounders. Results We identified 10 713 CRC surgery patients. A total of 2000 patients had AKI and were included. Thirty-day mortality was 16.5% (95% CI 13.7-19.8), 16.2% (95% CI 11.3-22.8), and 13.4% (95% CI 11.6-15.4) for current, former, and non-users. Adjusted HR was 1.26 (95% CI 0.96-1.65) and 1.19 (95% CI 0.78-1.82) for current and former users compared with non-users. One-year mortality rates were 26.4% (95% CI 22.9-30.4), 29.8% (95% CI 23.2-37.8), and 24.7% (95% CI 22.4-27.2) in current, former, and non-users. Compared with non-users, the adjusted 1-year HR for death in current and former users were 1.29 (95% CI 0.96-1.73) and 1.11 (95% CI 0.91-1.35). Conclusion Based on our findings, current users of ACE-I/ARB may possibly have a small increase in mortality rate in the year after post-operative AKI, although the degree of certainty is low.