Prevalence of acute kidney injury following cardiac surgery and related risk factors in Chinese patients

Abstract

Background/aims: Acute kidney injury (AKI) following surgery is a major complication, but the prevalence and risk factors in the Asian population are unclear. Recently, a consensus definition of AKI (AKIN) was proposed. We studied a cohort of cardiac surgery patients and identified AKI by AKIN and associated risk factors.

Methods: We retrospectively evaluated 1,056 consecutive patients undergoing cardiac surgery in Renji Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China from January 1, 2004 to June 30, 2007. We recorded AKIN stage, clinical characteristics, perioperative variables and complications, as well as clinical outcomes. Univariate and multivariate regression as well as survival analysis was performed.

Results: AKI occurred in 328 (31.1%) patients, stage 1 in 21.1%, stage 2 in 6.3% and stage 3 in 3.7%. Patients with AKI were older (65.8 vs. 53.5 years, p < 0.001), more often male (66.8 vs. 54.1%, p < 0.001), and had higher Charlson Comorbidity Index (CCI) (CCI >2: 22.6 vs. 7.8%, p < 0.001). In logistic regression, advanced age (OR 1.48 per decade, 95% CI 1.32-1.67), CCI >2 (OR 2.82, 95% CI 1.80-4.41), hypertension (OR 2.13, 95% CI 1.47-3.09), left ventricular ejection fraction (LVEF) <45% (OR 1.97, 95% CI 1.14-3.40), postoperative central venous pressure (CVP) <6 cm H(2)O (OR 13.28, 95% CI 8.72-20.14) and postoperative use of ACEI/ARB (OR 1.90, 95% CI 1.27-2.85) were risk factors of AKI. Mortality rose progressively with increased AKIN stage (non-AKI 0.7%, stage 1 4.9%, stage 2 12.1% and stage 3 48.7%). In ROC analysis, AKIN classification was identified to be associated with in-hospital mortality with an AUC of 0.865 (95% CI 0.801-0.929, sensitivity 0.884, specificity 0.714, p < 0.001). Finally, in a Cox proportional hazards model, AKIN stage (HR 2.40, p < 0.001), re-exploration (HR 6.30, p = 0.002) and multiple organ dysfunction syndrome (MODS) (HR 4.42, p = 0.001) were associated risk factors for in-hospital mortality.

Conclusion: We evaluated AKIN as a marker of AKI and mortality risk in a large, unselected Chinese cohort of incident patients undergoing cardiac surgery. AKI following cardiac surgery was diagnosed by AKIN criteria in around one third of the patients, and AKI may be associated with outcome. The value of preventative strategies to reduce AKI and their effect on in-hospital mortality should be studied.