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.