Objective Acute kidney injury (AKI) is a common complication after cardiac surgery,especially in elderly patients,and related with poor prognosis.Although much advances in therapies of AKI have been obtained,the prognosis of patients did not improved.In the absence of proven interventions,a reasonable strategy would be to identify modifiable risk factors for AKI.The objective of the present study was to explore modifiable risk factors of acute kidney injury after cardiac surgery with cardiopulmonary bypass in elderly patients.Methods Data from 457 consecutive elderly patients (age ≥60 years old)who underwent cardiac surgery with cardiopulmonary bypass in the Guangdong General Hospital between January 2007 and December 31,2009 were analyzed in this retrospective research.The primary outcome was AKI according to the serum creatinine criteria of the RIFLE (renal Risk,Injury,Failure,Loss of renal function and End-stage renal disease) classification as an increase in serum creatinine ＞ 50％ from baseline to peak value within the first seven postoperative days.The baseline serum creatinine was defined as the latest serum creatinine before cardiac surgery.Univariate anadysis was carried out for patients'demographics data and multivariate analysis by logistic regression was used to obtain the independent risk factors for AKI.Results Among 457 elderly patients,patients mean age was (65.22 ± 4.17) years and they comprised 253 (55.4％) men and 204 (44.6％) women.AKI occurred in 313 (68.5 ％) participants.Compared with patients without postoperative AKI,the media length of intensive care unit was longer in patients with postoperative AKI,4.0 (2.0-7.5) days versus 2.0 (1.0-3.0) days,respectively.In logistic regression model,malc (odds ratio[OR] 1.894,95％ confidence interval[CI] 1.136-3.157),age above 65 years (OR 2.391,95％ CI 1.381-4.142),hypertension (OR 2.286,95％ CI 1.249-4.184),estimated glomerular filtration rate less than 60 ml/min (OR 1.933,95％ CI 1.111-3.362),preoperative uric acid ＞ 450 μ mol/L (OR 2.938,95％ CI 1.633-5.285),use of angiotensin converting enzyme inhibitors/angiotensin receptor inhibitors (ACE1/ARB) before cardiac surgery (OR 2.196,95％ CI 1.283-3.759),use of ACEL/ARB after surgery (OR 0.329,95％ CI 0.156-0.691),use of diuretics (OR 0.149,95％ CI 0.068-0.326),time of cardiopulmonary bypass above 120 min (OR 5.228,95％ CI 3.023-9.041) and prolonged mechanical ventilation (OR 2.921,95％ CI 1.527-5.586) were independent factors of AKI after cardiac surgery with cardiopulmonary bypass.Conclusion Preoperative uric acid above 450μmol/L was a modifiable risk factor of AKI after cardiac surgery with cardiopulmonary bypass in elderly patients.Therapies aimed at mitigating high preoperative uric acid may offer protection against this complication.

OBJECTIVETo investigate the impact of pre-operative uric acid on acute kidney injury (AKI) after cardiac surgery in elderly patients.

METHODSClinical 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.

RESULTSAmong 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).

CONCLUSIONPre-operative elevated uric acid is an independent risk factor of AKI after cardiac surgery in elderly patients.

Acute Kidney Injury ; etiology ; Aged ; Angiotensin Receptor Antagonists ; Angiotensin-Converting Enzyme Inhibitors ; Cardiac Surgical Procedures ; adverse effects ; Cardiopulmonary Bypass ; Coronary Artery Bypass ; Female ; Humans ; Incidence ; Kidney Function Tests ; Male ; Middle Aged ; Predictive Value of Tests ; Risk Factors ; Uric Acid ; blood

Objective To evaluate the value of proteinuria in predicting acute kidney injury (AKI) after cardiac surgery in elderly patients.Methods To retrospectively analyze the perioperative clinical data of elderly patients (age 60 or older)undergone cardiac surgery with cardiopulmonary bypass at Guangdong General Hospital from January 2005 to December 2010.Target patients were divided into two groups according to AKI defined by the KDIGO criteria.Data for those two groups were examined by single-factor analysis,and then logistic regression analysis was used to further determine independent factors of AKI after cardiac surgery.Results Among 848 elderly patients,AKI occurred in 524(61.8％) participants,including 39.2％(n=332)at AKI stage 1,16.6％ (n =141) at AK I stage 2,and 6.0 ％ (n=51) at AKI stage 3.A total of 15.9 ％ of patients(n=135) had preoperative proteinuria,including 12.4 ％ (n =106) with mild proteinuria,and 3.5 ％ (n =30) with heavy proteinuria.Logistic regression analysis showed that proteinuria was correlated with postoperative AKI.With the increase of proteinuria,the risk of AKI also increased,and the OR values of mild and severe proteinuria were 1.758 (1.020-3.029) and 4.758 (1.326-17.077),respectively.Conclusions Preoperative proteinuria may predict the occurrence of AKI after cardiac surgery in elderly patients.There is a gradual increase in the risk of AKI as proteinuria becomes more severe.Early institution of therapeutic interventions may be used in elderly patients with preoperative proteinuria undergoing cardiac surgery to attenuate the risk of AKI.