Neutrophil, Lymphocyte, and Platelet Counts and Acute Kidney Injury After Cardiovascular Surgery

Postoperative low platelet count and perioperative high neutrophil/lymphocyte (N/L) ratio are associated with acute kidney injury (AKI) and mortality after cardiac surgery. The authors investigated whether (1) their combination neutrophil/lymphocyte × platelet (N/LP) ratio is an independent predictor of AKI and postoperative mortality and (2) whether the N/LP ratio increases predictive ability compared with the N/L ratio or platelet nadir.This was a retrospective and observational study.Single large university hospital.The study comprised 1,099 adult patients who underwent cardiovascular surgeries with cardiopulmonary bypass.Baseline clinical parameters including platelet counts, the N/L ratio, and the N/LP ratio measured before surgery, immediately after surgery, and on postoperative days 1 and 2 were obtained. Multivariable analysis revealed that the maximal N/LP ratio was an independent predictor of AKI and 5-year mortality. Propensity score matching was performed between the high and low preoperative N/LP ratio groups. Significant differences in the mortality rate and incidence of AKI also were found in the matched cohort. The area under the receiver operating characteristic curve (AUC) of the maximal N/LP ratio as a continuous variable was significantly higher than the AUC of the maximal N/L ratio or nadir platelet as continuous variables (maximal N/LP ratio: 0.62 v N/L ratio: 0.59; p = 0.026 v platelet nadir: 0.57; p = 0.003). The AUC of multivariable risk prediction with the maximal N/LP ratio (0.77) was significantly higher than the AUC without the N/LP ratio (0.70; p < 0.0001).High N/LP ratios were associated with postoperative AKI and 5-year mortality. The N/LP ratio may assist with the the prediction of AKI and mortality in high-risk cardiovascular surgery.