Background: Acute kidney injury (AKI) is a common complication after cardiovascular surgery. The use of renin angiotensin system (RAS) blockers preoperatively is controversial due to conflicting results of their effect on the incidence of postoperative AKI and mortality.

Study design: Meta-analysis of prospective or retrospective observational studies (1950 to January 2013) using MEDLINE, EMBASE, the Cochrane Library, conferences, and ClinicalTrials.gov, without language restriction.

Setting & population: Patients undergoing cardiovascular surgery.

Selection criteria for studies: Retrospective or prospective studies evaluating the effect of preoperative use of RAS blockers in the development of postoperative AKI and/or mortality in adult patients.

Intervention: Preoperative use of RAS blockers. RAS-blocker use was defined as long-term use of either angiotensin-converting enzyme inhibitors or angiotensin receptor blockers until the day of surgery.

Outcomes: The primary outcome was the development of postoperative AKI; the secondary outcome was mortality. AKI was defined by different authors using different criteria. Death was ascertained in the hospital, at 30 days, or at 90 days in different studies.

Results: 29 studies were included (4 prospective and 25 retrospective); 23 of these involving 69,027 patients examined AKI, and 18 involving 54,418 patients studied mortality. Heterogeneity was found across studies regarding AKI (I2 = 82.5%), whereas studies were homogeneous regarding mortality (I2 = 20.5%). Preoperative RAS-blocker use was associated with increased odds for both postoperative AKI (OR, 1.17; 95% CI, 1.01-1.36; P = 0.04) and mortality (OR, 1.20; 95% CI, 1.06-1.35; P = 0.005).

Limitations: Lack of randomized controlled trials, different definitions of AKI, different durations of follow-up used to analyze death outcome, and inability to exclude outcome reporting bias.

Conclusions: In retrospective studies, preoperative use of RAS blockers was associated with increased odds of postoperative AKI and mortality in patients undergoing cardiovascular surgery. A large, multicenter, randomized, controlled trial should be performed to confirm these findings.