CAR identified as Risk Factor for 28-Day ICU Mortality in Cardiac Surgery Patients: Study

The research, based on MIMIC-IV database information, examined the correlation between CAR levels and patient outcomes and found a clear dose–response relationship. CAR has been identified as a predictive marker in multiple postoperative contexts previously, but its prognostic association with cardiac surgery outcomes is not understood. This study sought to assess the correlation between CAR and ICU 28-day mortality, investigate subgroup-specific risk, and examine mechanisms through mediation analysis.

Methods

The research employed data from the MIMIC-IV database for 5,670 patients who were admitted to the ICU following cardiac surgery. Patients were divided into three groups according to CAR levels:

• Low CAR (<0.23)

• Intermediate CAR (0.23–0.31)

• High CAR (≥0.31)

Kaplan–Meier survival analysis was used to compare differences in 28-day mortality across the groups. Multivariate Cox regression and RCS analyses were applied to investigate the dose–response relationship between CAR and risk of mortality. Receiver operating characteristic (ROC) curves were used to establish the predictive validity of CAR. Mediation analysis was employed to investigate the way CAR affects mortality via biochemical markers.

Key Results

• Out of the 5,670 patients, those who had high CAR (≥0.31) had a mortality rate of 11.4% in ICU at 28 days, significantly greater than the patients with low CAR (<0.23) who had a mortality rate of 1.83%.

• Kaplan–Meier analysis revealed that high CAR patients had the lowest survival rate among the three groups (p < 0.0001).

• ROC curve analysis revealed that CAR had moderate predictive ability for 28-day ICU mortality (AUC = 0.748).

• There was a strong dose–response relationship, with increasing CAR levels correlating with increased risk of death.

• Subgroup analysis proved that the risk attributable to increased CAR was augmented in female patients and in the absence of chronic conditions such as CKD and T2DM.

Mediation analysis indicated that CAR affected 28-day ICU mortality via primary biomarkers, such as:

• Chloride (39.8%)

• Potassium (24.4%)

• Sodium (28.3%)

• Glucose (11.8%)

The study authors concluded that CAR is a reliable predictor of 28-day ICU mortality in cardiac surgery patients. The dose dependency and biochemical mediation effects indicate that CAR can potentially be used as an important instrument for early risk stratification.

Reference:

Shi, P., Rui, S. & Meng, Q. Association between serum creatinine—to—albumin ratio and 28-day mortality in intensive care unit patients following cardiac surgery: analysis of mimic-iv data. BMC Cardiovasc Disord 25, 100 (2025). https://doi.org/10.1186/s12872-025-04505-1