Off-Pump Coronary Artery Bypass Surgery and Acute Kidney Injury: A Meta-analysis of Randomized and Observational Studies

Background: Acute kidney injury (AKI) after coronary artery bypass grafting (CABG) is associated with significant morbidity and mortality. Controversy exists regarding whether an off-pump technique can reduce post-CABG renal injury. Study Design: Systematic review and meta-analysis. Setting & Population: Adult patients undergoing CABG. Selection Criteria for Studies: MEDLINE, EMBASE, Cochrane Renal Library, and Google Scholar were searched in May 2008 for randomized controlled trials (RCTs) and observational studies comparing off-pump CABG (OPCAB) with conventional CABG (CAB) for renal outcomes. Studies involving patients on long-term renal replacement therapy (RRT) were excluded. Intervention: OPCAB. Outcomes: Primary outcomes were overall AKI and AKI requiring RRT. Results: 22 studies (6 RCTs and 16 observational studies) comprising 27,806 patients met the inclusion criteria. The pooled effect from both study cohorts showed a significant reduction in overall AKI (odds ratio [OR], 0.57; 95% confidence interval [CI], 0.43 to 0.76; P for effect < 0.001; l(2) = 67%; P for heterogeneity < 0.001) and AKI requiring RRT (OR, 0.55; 95% Cl, 0.43 to 0.71; P for effect < 0.001; l(2) = 0%; P for heterogeneity = 0.5) in the OPCAB group compared with the CAB group. In RCTs, overall AKI was significantly reduced in the OPCAB group (OR, 0.27; 95% Cl, 0.13 to 0.54); however, no statistically significant difference was noted in AKI requiring RRT (OR, 0.31; 95% Cl, 0.06 to 1.59). In the observational cohort, both overall AKI (OR, 0.61; 95% Cl, 0.45 to 0.81) and AKI requiring RRT (OR, 0.54; 95% Cl, 0.40 to 0.73) were significantly less in the OPCAB group. RCTs were noted to be underpowered and biased toward recruiting low-risk patients. Sensitivity analysis restricted to good-quality studies showed a significant reduction in AKI. Limitations: Lack of uniform AKI definition in the included studies, heterogeneity for overall AKI outcome. Conclusions: Analysis of the current evidence suggests a reduction in AKI using the OPCAB technique; however, studies lack consistency in defining AKI. Available RCTs are underpowered to detect a difference in AKI requiring RRT; evidence from observational studies suggests a reduction in RRT requirement. Future studies should apply a standard definition of AKI and target a high-risk population. Am J Kidney Dis 54:413-423. (C) 2009 by the National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.