Applicability of the Cleveland clinic scoring system for the risk prediction of acute kidney injury after cardiac surgery in a South Asian cohort

Background: Acute kidney injury (AKI) after cardiac surgery is a frequent post-operative complication associated with an increased risk of mortality, morbidity and hospital costs. Preoperative risk scores such as the Cleveland Clinic Scoring Tool (CCST) have been validated in Western population group to identify patients at higher risk of AKI and may facilitate preventive strategies. However, the scoring tool has not been validated systematically in a South Asian cohort. We aimed to evaluate the applicability of the CCST in prediction of AKI after open cardiac surgery in a South-Indian tertiary care center.

Materials and methods: A retrospective study of all patients who underwent elective open cardiac surgery over a 4year period from Jan 2012 to Dec 2015 at a single centre were included and relevant details extracted from a comprehensive chart review. The primary outcome was AKI as defined by the Kidney Disease Improving Global Outcomes (KDIGO) criteria. Patients were risk stratified as per the CCST to assess for prediction of AKI into low risk (0-2), intermediate risk (3-5) and high risk (>6) groups.

Results: A total of 276 patients underwent open cardiac surgery with mean age of 51.5±13.06 yrs. This included 177 (64.1%) males and 99 females (35.8%). Overall incidence of AKI was 6.88%. Mean age, gender, BMI, preoperative serum creatinine, diabetes mellitus, chronic obstructive pulmonary disease, cardiopulmonary bypass time was similar in patients who developed AKI vs those who did not have AKI postoperatively. The mean CCST scores were 1.6 in those without AKI, 1.5 in stage 1, 3.0 in stage 2 and 3.4 in stage 3 AKI. Higher risk scores predicted greater risk of AKI. A total of 106 patients (38.4%) were on ACE/ARB, 119 patients (43.1%) received beta-blockers, 110 (39.8%) received diuretics while 144(52.1%) had received preoperative statins. Comparison of drug use between the two groups revealed that preoperative use of ACEI/ARB was associated with highest risk of AKI (p=0.006). Mortality rate was also high at 15.7% in those with AKI compared to 3.1% in non-AKI group (p=0.04).

Conclusion: The modified CCST was valid in risk identification of patients with severe stage of AKI but did not have strong discrimination for early AKI stages. Preoperative statin use did not protect against AKI in our study, however preoperative ARB/ACEI use was significantly associated with occurrence of postoperative AKI.