Background: An increase in neutrophils and a decrease in platelets have been correlated with a heightened risk of acute kidney injury (AKI) following cardiac surgery. However, the combined metric of Neutrophil-to-Platelet Ratio (NPR) and its association with post-surgery AKI risk has not yet been investigated.

Objective: To explore the relationship between NPR and AKI risk within seven days following cardiac surgery.

Methods: Data were downloaded from Medical Information Mart for Intensive Care, including patients after cardiac surgery. Both univariate and multivariate logistic regression models were employed to explore association between NPR and AKI risk within seven days post-operatively. A restricted cubic spline was employed to evaluate non-linear nature of this association. Subgroup analyses were performed to examine variations across different cohorts.

Results: 1,702 patients were included, with an AKI incidence of 20.21% within the postoperative seven-day period. Logistic regression analysis revealed that, in fully adjusted models, the highest tertile (T3, NPR ≥ 7.453) was significantly associated with an elevated AKI risk within seven days post-surgery (OR=1.500, 95%CI: 1.086-2.076, P=0.014). There was no significant non-linear relationship between NPR and AKI risk (P-overall =<0.001, P-non-linear=0.468Notably, a significant interaction was observed in the subgroup receiving platelet transfusion (P interaction = 0.005).

Conclusion: In adults undergoing cardiac surgery, an elevated NPR was linked to higher AKI risk. This finding offers a novel marker for the early identification of patients at high risk for AKI post-surgery.