Preoperative statin therapy is not associated with a reduced incidence of postoperative acute kidney injury after cardiac surgery

Background: Our objective was to examine the association between preoperative statin therapy and the prevalence of postoperative acute kidney injury (AKI) in patients undergoing cardiac surgery with the use of cardiopulmonary bypass. Methods: We performed a retrospective investigation of 10,648 consecutive patients undergoing coronary artery bypass grafting using cardiopulmonary bypass and/or valve surgery between January 2002 and December 2006. Patients were divided into 2 groups depending on preoperative therapy with statin drugs. The primary outcome was postoperative AKI based on the RIFLE (Risk, Injury, Failure, Loss, End-stage) criteria. Secondary outcomes included requirement for postoperative dialysis and hospital mortality. Multivariable logistic regression models were developed for the primary and secondary outcomes. To control for selection bias related to statin therapy, a propensity score was developed using a greedy matching technique. Results: The incidence of AKI was 12.1% (n = 1286). AKI occurred in 13.31% of patients receiving preoperative statins (819 of 6152 patients) versus 10.41% in the no statin group (467 of 4487 patients) (P < 0.001). The incidence of postoperative dialysis was 1.71% (n = 182). Postoperative dialysis was needed in 1.75% of patients in the statin group (108 of 6157 patients) compared with 1.65% of patients (74 of 4491 patients) in the no statin group (P = 0.68). Hospital mortality after surgery occurred in 1.71% (n = 182) of patients. The incidence of mortality for patients in the statin group was 1.71% (105 of 6157 patients) and this was not different from mortality in the no statin group of 1.71% (77 of 4491 patients) (P = 0.97). In multivariate logistic regression analysis, statin therapy was not associated with AKI (odds ratio [OR] 0.97, 95% confidence interval [CI] 0.84-1.12; P = 0.68), postoperative dialysis (OR 0.80, 95% CI 0.55-118; P = 0.23), or hospital mortality (OR 0.803, 95% CI 0.56-1.16; P = 0.24). In 2646 propensity-matched pairs, the incidence of AKI was 12.0% in the statin group versus 12.8% in the no statin group (P = 0.38). The statin group had a 1.63% incidence of postoperative dialysis versus 2.08% in the no statin group (P = 0.22). In the same propensity-matched population, hospital mortality occurred in 1.63% of patients in the statin group compared with 2.1% in the no statin group (P = 0.19). Conclusion: These results suggest that previously reported reductions in perioperative mortality for patients taking preoperative statins and undergoing cardiac surgery is likely not mediated through a reduction in postoperative AKI.