Effect of Postoperative International Normalized Ratio on AKI Incidence Following Valve Replacement Surgery

Background: This study aims to investigate the impact of the international normalized ratio (INR) following valve replacement surgery on the incidence of postoperative acute kidney injury (AKI). Methods: A retrospective review of medical records was conducted for patients hospitalized at Beijing Anzhen Hospital who underwent valve replacement surgery and were prescribed warfarin between August 2018 and August 2023. Patients were divided into two groups based on the presence or absence of postoperative AKI: the AKI group and the non-AKI group. Comparative analyses of medical records were performed between these two groups. Logistic regression and restricted cubic splines analysis were used to evaluate the association between postoperative INR levels and the occurrence of AKI. Furthermore, patients with AKI were stratified into four subgroups based on postoperative INR levels, and differences in renal function recovery and in-hospital mortality among these subgroups were subsequently analyzed. Results: The study included a cohort of 8,497 patients, of whom 58.6% were male, with an average age of 57.40 ± 12.27 years. Postoperative AKI was observed in 15.9% of the patients. An increase in the INR was correlated with a progressive rise in the incidence of AKI and in-hospital mortality. Multivariate regression analysis revealed that, compared to patients with an INR <2, those with an INR between 2 and 3 had a 2.9-fold increased risk of developing AKI, those with an INR between 3 and 4 had a 4.1-fold increased risk, and those with an INR≥4 had a 5.2-fold increased risk. Additionally, restricted cubic splines analysis demonstrated that elevated INR levels were significantly associated with a higher risk of postoperative AKI (nonlinear P-values all <0.001). Among patients who developed AKI, increased INR levels were linked to a reduced rate of renal function recovery during hospitalization and a higher in-hospital mortality. Conclusion: Elevated INR following valve replacement surgery is independently associated with an increased risk of postoperative AKI.