Association between serum creatinine—to—albumin ratio and 28-day mortality in intensive care unit patients following cardiac surgery: analysis of mimic-iv data

BACKGROUND: Creatinine-to-albumin ratio (CAR) has been recognized as a predictive indicator in the postoperative setting. However, its relationship with outcomes in patients receiving cardiac surgery remains elusive. This study aimed to discuss the link between CAR and 28-day mortality in patients admitted to intensive care unit (ICU) following cardiac surgery, hoping to provide some insights for targeted interventions for improvement of patient outcomes. METHODS: MIMIC-IV database was searched to obtain data of patients admitted to ICU following cardiac surgery. Retrieved patients were split into three groups based on CAR levels. The 28-day ICU mortality in each group was evaluated and compared using Kaplan-Meier analysis. Subgroup analysis, multivariate Cox regression and restricted cubic spline (RCS) analysis were used to further examine the relationship between CAR and outcomes. Receiver operating characteristic (ROC) curves were used to assess the predictive ability of CAR. Mediation analysis was conducted to investigate the potential mechanism by which CAR affects 28-day ICU mortality. RESULTS: A total of 5,670 patients were included and divided into three groups. Patients with high CAR values (CAR ≥ 0.31) had a significantly increased rate of 28-day ICU mortality (11.4%), as compared to those with low CAR levels (CAR < 0.23, 1.83%). In addition, patients with high CAR values (CAR ≥ 0.31) had a lowest survival rate than the other two groups (p < 0.0001). ROC curve analysis showed that CAR exhibited a moderate predictive power (AUC = 0.748). Moreover, CAR was identified as a strong risk factor for 28-day ICU mortality, and a significant dose-response association was presented. Further subgroup analysis revealed pronounced mortality risks in females and patients without chronic conditions such as chronic kidney disease (CKD) and type 2 diabetes mellitus (T2DM). Mediation analysis indicated that CAR affected 28-day ICU mortality through biomarkers like chloride (39.8%), glucose (11.8%), potassium (24.4%), and sodium (28.3%). CONCLUSION: CAR served as a risk factor for 28-day ICU mortality in patients receiving cardiac surgery, and it showed a complex dose-response and subgroup-specific association with 28-day ICU mortality. Additionally, CAR affected 28-day ICU mortality through multiple key biomarkers, providing some insights for targeted interventions.