Background~Knee arthroscopy is the most commonly performed orthopaedic procedure worldwide, with, according to the American Society for Sports Medicine, over 4 million procedures performed each year. The risk of venous thrombosis following this procedure is considerable with rates of symptomatic events varying between 0.9% and 4.6%.~It is currently unknown how this high risk comes about considering its short duration and minimal tissue damage caused by the procedure. A factor that may play a role is the use of a tourniquet. A large majority of orthopaedic surgeons prefer to operate within a 'dry field', which is obtained by the use of a tourniquet. In the proposed study the investigators will investigate the effect of a tourniquet on local and systemic markers of hypoxia, inflammation, involvement of endothelium, and coagulation activation.~Objective~To investigate the effect of tourniquet application on the coagulation system in patients undergoing a knee arthroscopy. A finding of more prominent activation of the coagulation system with tourniquet use than with non-use will create an important opportunity to prevent thromboembolic events in these patients, as it has been shown that knee arthroscopy can be performed adequately without the use of a tourniquet. Furthermore, it will increase the understanding of the pathophysiology of thrombosis.~Study Design~In a randomized, controlled clinical study the investigators will compare local and systemic coagulation and inflammation markers before and after knee arthroscopy between two groups: 25 patients will be randomized to arthroscopy with tourniquet (Group I) and 25 patients to arthroscopy without tourniquet (Group II).~Inclusion and exclusion criteria~The patients will be recruited from one hospital in Gouda over a 6 months inclusion period. All patients over 18 years, scheduled for a meniscectomy, diagnostic arthroscopy or removal of corpora libera will be eligible for inclusion. Patients will be excluded when they suffer from any kind of coagulation disorder, use of hormonal anticonception, in case of pregnancy or puerperium, when they have a history of venous thrombosis, had major surgery or cast-immobilisation of the lower extremity in the past two months, have a neoplasm or inflammatory disease, have a BMI>30, or when they use anticoagulant therapy. Patients will generally receive spinal anaesthesia. Patients who are nevertheless exposed to any other type of anaesthesia will be excluded as well, to keep the effect of anaesthesia equal for all participants.~Intervention~Patients will be randomized to knee arthroscopy without tourniquet use and to knee arthroscopy with tourniquet use. In patients randomized to arthroscopy with tourniquet use, exsanguination in the leg in which the knee arthroscopy will be performed will be accomplished by raising the leg vertically for one minute. The tourniquet will be inflated to 100-150 mmHg above systolic blood pressure.~Data on duration of surgery and duration of tourniquet use will be collected. Blood collected from the cubital vein and the great saphenous vein during arthroscopy of the knee will be analyzed on outcome parameters that reflect a hypoxic state, an inflammatory reaction, involvement of the endothelium, a procoagulant state and thrombin formation.~Main study endpoints (primary)~Change in parameters between timepoints; Before surgery (blood drawn approximately 1 hour before surgery), directly after surgery (blood drawn within 5 minutes), 1 hour after surgery will be analyzed.~Different patterns will be analyzed to explore the effect of tourniquet application on the coagulation system by possible biological mechanism. A change (increase or decrease) of markers within one pattern, compared to baseline measurements (before surgery), is considered as a relevant shift of that pattern, thereby suggesting the involvement of that specific pathway.~Outcome parameters that reflect a hypoxic state:~pH~pO2~pCO2~Lactate~Outcome parameters that reflect an inflammatory reaction:~White Blood Cell Count (WBCC)~E-selectin~Neutrophil Extracellular traps (NETs)~Outcome parameters that reflect involvement of the endothelium:~Von Willebrand Factor (vWF)~Thrombomodulin~E-selectin~Outcome parameters that reflect a procoagulant state and thrombin formation:~Prothrombin fragments 1+2~D-dimer~Plasmin Activator Inhibitor 1 (PAI 1)~Tissue plasminogen activator (tPA)~Factor VIII~Thrombin and Antithrombin complexes (TAT)~Plasmin and antiplasmin complexes (PAP)~Secondary study paramaters~• Visibility during arthroscopy and technical difficulty score.~Time Schedule~Month 1-3: Completion of study protocol, procedure for approval by METC. Set up of database and randomisation procedure. Instruction of participating clinicians and surgery/anaesthesia staff.~Month 4-6: Inclusion of patients, data collection. Month 7-8: Laboratory tests. Month 9-12: Data analysis, writing and submission of manuscript.
Knee arthroscopy is the most commonly performed orthopaedic procedure worldwide, with, according to the American Society for Sports Medicine, over 4 million procedures performed each year. The risk of venous thrombosis following this procedure is considerable with rates of symptomatic events varying between 0.9% and 4.6%. It is currently unknown how this high risk comes about considering its short duration and minimal tissue damage caused by the procedure. A factor that may play a role is the use of a tourniquet. A large majority of orthopaedic surgeons prefer to operate within a 'dry field', which is obtained by the use of a tourniquet. Tourniquet applied surgery is not without risks. Although its use during orthopedic surgery is widely accepted and a standard procedure, tourniquet use can lead to loss of muscle functional strength and contractile speed, vessel wall damage and nerve injury, next to the possibly increased risk of venous thrombosis. In the proposed study the investigators will investigate the effect of a tourniquet on local and systemic markers of hypoxia, inflammation, involvement of endothelium, and coagulation activation. A finding of more prominent activation of the coagulation system with tourniquet use than with non-use will create an important opportunity to prevent thromboembolic events in these patients, as it has been shown that knee arthroscopy can be performed adequately without the use of a tourniquet. Furthermore, it will increase the understanding of the pathophysiology of thrombosis.