The association of preoperative statin use and acute kidney injury after noncardiac surgery.

BACKGROUND Our objective was to examine the association between preoperative statin therapy and the incidence of postoperative acute kidney injury (AKI) in patients undergoing elective noncardiac surgery. METHODS We analyzed the electronic records of 57,246 patients who had elective noncardiac surgery at the Cleveland Clinic Main Campus between December 2004 and March 2010. Patients were divided into 2 groups depending on preoperative therapy with statin drugs. Our primary outcome was AKI, defined as "risk," "injury," or "failure" using the RIFLE (Risk, Injury, Failure, Loss, and End-stage Kidney) criteria. Secondary outcomes included postoperative dialysis and all-cause hospital mortality. Each statin user was matched to a nonuser based on propensity scores. The propensity scores were estimated using a multivariable logistic regression model, incorporating all available baseline potential confounders. After the propensity-matching procedure, we performed final analyses for the primary and secondary outcomes. For the primary analysis, we used a univariable logistic regression model to estimate the odds ratio (OR) (and 95% confidence intervals) for AKI, postoperative dialysis, and hospital mortality between matched statin users and nonusers. RESULTS Of the total group, 23,745 records were unusable because of missing data. Among the remaining 28,508 patients analyzed, the overall incidence of AKI was 6.1%. Three hundred sixty-one of 4805 statin users (7.5%) and 1377 of 23,703 nonusers (5.8%) experienced AKI. The incidence of postoperative dialysis was 0.05%. Six statin users (0.12%) and 8 nonusers (0.03%) required dialysis postoperatively. The incidence of hospital mortality was 0.62%. Mortality was observed for 47 patients (1.0%) and 130 patients (0.5%), respectively. Among 4172 matched pairs, the incidence (95% confidence interval) of AKI was 7.1% (6.2%, 8.1%) in the matched statin users and 8.0% (7.1%, 9.0%) in the nonusers, corresponding to an OR of 0.88 (0.75, 1.03), which was not statistically significant (P = 0.12, χ(2) test). The secondary outcomes were also not significantly different in matched statin users and nonusers. Postoperative dialysis was required for 0.10% (0.02%, 0.33%) and 0.12% (0.04%, 0.37%) of patients in the respective groups (OR = 0.80 [0.16, 3.70]; P = 0.74). Hospital mortality occurred in 1.0% (0.7%, 1.5%) and 1.3% (0.9%, 1.8%) of patients, respectively (OR = 0.76 [0.47, 1.20]; P = 0.18). CONCLUSIONS Our data did not support the hypothesis that preoperative statin therapy in doses routinely used to treat hypercholesterolemia is associated with a change in the incidence of AKI, postoperative dialysis, or hospital mortality in patients undergoing noncardiac surgery.