© Acta Anæsthesiologica Belgica, 2021, 72, n° 1 Abstract : Background : During orthopedic surgery, the use of a pneumatic tourniquet results in side effects secondary to ischemia-reperfusion phenomena. We tested the hypothesis that total knee arthroplasty with a tourniquet is associated with increase in plasma concentrations of biomarkers of neutrophil activation and endothelial injury. The second aim was to compare these changes during spinal or general inhalational anesthesia. Methods : 40 adult ASA I-II patients scheduled for total knee arthroplasty with a tourniquet under spinal or sevofurane anesthesia were included. Venous blood samples were collected before surgery, 1 h, 3 h, and 24 h after tourniquet defation. To assess neutrophil activation, plasma concentrations of total and active fractions of myeloperoxidase, as well as elastase concentrations and proteolytic activity were measured. Endothelial injury was assessed by measurement of plasma concentrations of syndecan-1, soluble thrombomodulin, soluble E-selectin, and vascular endothelial growth factor. Results were analyzed with a two-way analysis of variance. P< 0.05 was considered statistically signifcant. Results : Plasma concentrations of active but not total myeloperoxidase and elastase signifcantly increased following tourniquet defation. The level of syndecan-1, soluble thrombomodulin, soluble E-selectin, but not vascular endothelial growth factor, signifcantly de- creased postoperatively. These changes of biomarkers were similar during spinal and sevofurane anesthesia. Conclusions : Total knee arthroplasty with pneumatic tourniquet is associated with systemic release of markers of neutrophil activation which was comparable during spinal or sevofurane anesthesia. Systemic expression of endothelial injury was not detected in our clinical conditions. Keywords : Knee arthroplasty ; pneumatic tourniquet ; ischemia-reperfusion ; neutrophils ; endothelium. IntroductIon During total knee arthroplasty (TKA), a pneumatic tourniquet is used to achieve a bloodless surgical feld and to improve visualization of ana- tomical structures. However, a pneumatic tourniquet is associated with deleterious clinical consequences among which limb swelling and pain, increased risk of deep venous thrombosis, nerve palsies, muscle weakness, higher incidence of postoperative wound complications, acute pulmonary embolism, and lung injury (1). Most of the symptoms of this so- called tourniquet syndrome result from ischemia- reperfusion that amplifes surgical infammatory response and contributes to vascular dysfunction (2). In case of ischemia-reperfusion, activated polymorphonuclear neutrophils play a major role and participate to tissue injury by releasing cytotoxic granular enzymes such as myeloperoxidase (MPO) and elastase (EL). Concomitantly, structure and function of endothelial cells are damaged which allows release of fragments of the glycocalyx such as syndecan-1 (SD-1), surface anticoagulant and adhesion molecules including the soluble form of thrombomodulin (s-TM) and soluble E-selectin (s- ES) as well as mitogenic factors like the vascular endothelial growth factor (VEGF) (3, 4). Volatile (Acta Anaesth. Belg., 2021, 72, 7-15) Grégory MInguet, Thierry Franck, Etienne cavalIer, Christophe danIel, Didier Serteyn, Jean-François BrIchant, Jean JorIS. (*) Department of Anesthesia and Intensive Care Medicine, University Hospital of Liège, Liège, Belgium. (**) Center for Oxygen Research and Development, Institute of Chemistry B6a and Department of Clinical Sciences, Anaesthesiology and Equine Surgery, Faculty of Veterinary Medicine, University of Liège, Liège, Belgium . (***) Department of Clinical Chemistry, University Hospital of Liège, Liège, Belgium. (****) Department of Orthopedic Surgery, University Hospital of Liège, Liège, Belgium. Corresponding author : Grégory Minguet, Department of Anesthesia and Intensive Care Medicine, University Hospital of Liège, Domaine Universitaire du Sart-Tilman, Batiment B35, B-4000 Liège, Belgium. Phone : + 32 4 366 71 79. Fax : + 32 4 366 76 36. Email: gminguet@chuliege.be Paper submitted on December 1, 2020 and accepted on March 10, 2021. Confict of interest : None A preliminary study to assess neutrophil and endothelial response to knee arthroplasty with the use of a tourniquet : effects of spinal or sevofurane anesthesia g. MInguet (*), t. Franck (**), e. cavalIer (***), c. danIel (****), d. Serteyn (**), J.F. BrIchant (*), J. JorIS (*)