Combined effect of anion gap and red cell distribution width on the risk of acute kidney injury after cardiac surgery.

Background: This study was to analyze the roles of red blood cell distribution width (RDW), anion gap (AG) levels and their combined effects on the risk of acute kidney injury (AKI) following cardiac surgery.

Methods: This cohort study extracted the data of 1951 participants aged ≥ 18 years with the assessment of AKI after cardiac surgery during ICU stay from MIMIC-IV database between 2008 and 2019. Receiver operator characteristic (ROC) curve was used to determine the optimal cut-off value AG and RDW. The associations between AG, RDW, and the combined effects of AG and effects were evaluated via univariable and multivariable Logistic models. Odds ratio (OR) with 95% confidence interval (CI) were imputed.

Results: Among all the participants, 831 participants had AKI, and 1120 did not have AKI. ROC curves revealed that the optimum cut of points of AG and RDW were 12.75 mmol/L, and 13.65%, respectively. Increased risk of AKI was found in patients after cardiac surgery with AG > 12.75 mmol/L (OR = 1.44, 95%CI 1.15-1.80) or RDW > 13.65% group (OR = 1.23, 95%CI 1.01-1.50). In comparison to subjects with AG ≤ 12.75 mmol/L and RDW ≤ 13.65%, AG > 12.75 mmol/L and RDW ≤ 13.65% (OR = 1.42, 95%CI 1.07-1.89), and AG > 12.75 mmol/L and RDW > 13.65% (OR = 1.75, 95%CI 1.24-2.47) were associated with increased odds of AKI in patients after cardiac surgery.

Conclusions: AG and RDW had combined effects on risk of AKI in patients after cardiac surgery, which might offer an insight for the management of patients after cardiac surgery.