Does Aspartate Aminotransferase to Alanine Aminotransferase Ratio Predict Acute Kidney Injury After Cardiac Surgery?

Background: Aspartate aminotransferase (AST) to alanine aminotransferase (ALT) ratio (AST/ALT) frequently is used in the diagnosis and prognosis of liver diseases, however it is also used in the diagnosis and prognosis of many other diseases, such as myocardial infarction, acute ischemic stroke, and peripheral artery disease. Acute kidney injury (AKI) is one of the most important complications after cardiac surgery and is one of the main causes of morbidity and mortality. The purpose of the study was to analyze the relationship between AST to ALT and AKI after isolated coronary artery bypass graft surgery (CABG).

Methods: We retrospectively reviewed the prospectively collected data of 253 adult patients, who underwent isolated CABG surgery with normal renal function (baseline serum creatinine value <1.4 mg/dL). Preoperative (T0) and postoperative day 1 and day 3 (T1 and T2) serum AST and ALT levels were analyzed, and AST/ALT was calculated. A preoperative AST/ALT of 1.22 was found to be the best cutoff point for predicting postoperative AKI. Kidney injury was interpreted, according to RIFLE classification. The effect of AST to ALT ratio on AKI after CABG was determined using logistic regression analysis, and the results were expressed as odds ratio (OR) with a 95% confidence interval (CI). A P value < .05 was considered statistically significant.

Results: Postoperative AKI occurred in 40 patients (15.8%). On logistic regression analysis, higher AST/ALT both preoperatively and postoperatively were associated with an increased incidence of postoperative AKI (T0: OR, 3.983; 95% CI, 1.940-8.180, P < .001, T1: OR, 2.760; 95% CI, 1.381-5.515, P = .004, T2: OR, 2.515; 95% CI, 1.195-5.294, P = .015).

Conclusion: Preoperative and postoperative elevated AST to ALT ratio seems to be associated with an increased incidence of AKI after elective isolated CABG surgery.