Systemic Immune-inflammation Index Predicts Acute Kidney Injury after Cardiac Surgery: A Retrospective Observational Study

Objectives: Inflammation plays an essential role in the development of postoperative acute kidney injury (AKI) in patients receiving cardiac surgery. The study aims to examine the predictive value of the systemic immune-inflammation index (SII), a new biomarker reflecting systemic inflammation, in the development of AKI following cardiac surgery in patients who had coronary artery bypass grafting (CABG).
Methods: Patients who received CABG operation in 2022 were retrospectively examined. The incidence of AKI 7 days postsurgery using Kidney Disease Improving Global Outcomes criteria was the primary outcome. The patients were classified into the AKI (n=160) and non-AKI groups (n=424). Patients were compared in terms of basic clinical features, operative characteristics, postoperative variables, and hematological indices derived from preoperative complete blood count analysis. The ability of SII to predict AKI was assessed using receiver-operating characteristic (ROC) curve analysis. Multivariate logistic regression analysis was used to determine the independent relationship between the development of SII and AKI.
Results: In this investigation, the incidence of AKI was 25.6%. eGFR, serum albumin, and hemoglobin were significantly lower in the AKI group, whereas body mass index, hypertension, serum creatinine, neutrophil–lymphocyte ratio, platelet–lymphocyte ratio, and SII were significantly greater. The preoperative SII cutoff of 651.7 predicted AKI with 65.0% sensitivity and 64.9% specificity. The area under the ROC curve was 0.718 (95% confidence interval 0.676–0.760).
Conclusion: Preoperative SII may be a simple, inexpensive, and useful prognostic biomarker in predicting postoperative AKI in patients undergoing CABG.