Coagulation and Inflammatory Responses After Tourniquet Release in Total Knee Arthroplasty: Association with Hemodynamic Instability.

Background: Tourniquet use during total knee arthroplasty (TKA) improves surgical visualization and limits blood loss but may also trigger ischemia-reperfusion-related hemodynamic instability. This study investigated coagulation and inflammatory responses after tourniquet release and their association with perioperative hemodynamic instability. Methods: This prospective observational cohort study included 22 patients aged 65-90 years undergoing unilateral TKA. Hemodynamic parameters, coagulation markers (D-dimer, INR, APTT), and inflammatory markers were measured at predefined perioperative time points. Hemodynamic instability was assessed using the modified shock index (MSI = HR/MAP). Non-parametric statistical analyses were performed. Results: The D-dimer and INR increased significantly after tourniquet release and remained elevated at 24 h (p < 0.001). APTT prolongation was transient (p = 0.001). The NLR and SII increased both early and late, whereas CRP showed a delayed rise. Δ analysis demonstrated temporal changes in coagulation parameters; however, no significant between-group differences according to MSI status were identified. Although ΔPeak IL-6 was higher in the unstable group, the difference was not statistically significant (p = 0.097). ROC analysis demonstrated moderate discriminative performance for ΔPeak IL-6 (AUC = 0.747), whereas the NLR (AUC = 0.471), SII (AUC = 0.529), and CAI (AUC = 0.482) showed poor predictive performance for hemodynamic instability. Conclusions: Tourniquet release induces significant coagulation and inflammatory responses following total knee arthroplasty. Although no definitive biomarker of hemodynamic instability was identified, ΔPeak IL-6 showed a trend toward association with instability and may merit further investigation. These findings suggest a possible interaction between inflammatory and coagulation pathways after tourniquet release and should be validated in larger prospective studies.