Objective: To investigate the impact of pre-operative uric acid on acute kidney injury (AKI) after cardiac surgery in elderly patients.
Methods: Clinical data were collected from 936 elderly patients (age ≥ 60 years) undergoing cardiac surgery with cardiopulmonary bypass in Guangdong General Hospital between January 2005 and May 2011. The baseline serum creatinine was defined as the latest serum creatinine before surgery, and AKI was diagnosed according to RIFLE criteria. Patients were divided into three groups according to the sex-specific cutoff values of serum uric acid tertiles (group A: ≤ 384.65 µmol/L in men, and ≤ 354.00 µmol/L in women; group B:384.66-476.99 µmol/L in men and 354.01-437.96 µmol/L in women; group C: ≥ 477.00 µmol/L in men and ≥ 437.97 µmol/L in women). Multivariate logistic regression analysis was used to analyze the independent risk factors for AKI.
Results: Among 936 elderly patients, 576 cases (61.5%) developed AKI. Mean uric acid concentration was higher in AKI patients than in Non-AKI patients ( (436.6 ± 119.1) µmol/L vs. (398.0 ± 107.2) µmol/L, P < 0.001). The incidence of AKI was 56.1% (175/312) in group A, 56.3% (175/311) in group B, 72.2% (226/313) in group C (P < 0.001). Multiple logistic regression analysis showed that, after adjusted for age, gender, co-morbidities(hypertension, diabetes mellitus, cerebrovascular disease, chronic obstructive pulmonary disease), previous cardiac surgery, eGFR<60 ml×min(-1) ×1.73 m(-2), heart function ≥ 3 (NYHA), positive urine protein, combination of coronary artery bypass grafting and valvular surgery, cardiopulmonary bypass operation time, aortic cross-clamping time, pre-operative angiotensin converting enzyme inhibitor or angiotensin II receptor blockers and lipid-lowering drugs use, early postoperative angiotensin converting enzyme inhibitor or angiotensin II receptor blockers, diuretics and digoxin use, post-operation central venous pressure, risk of post operative AKI was significantly higher in group C than in group A (OR:1.897, 95%CI: 1.270-2.833, P = 0.002).
Conclusion: Pre-operative elevated uric acid is an independent risk factor of AKI after cardiac surgery in elderly patients.