Femoral nerve block prevents deep venous thrombosis of the lower extremity after knee arthroplasty: a single-center randomized controlled trial

Background: The use of tourniquets in knee arthroplasty can promote the release of abundant neutrophil elastase from neutrophils, which increases the risk of deep venous thrombosis of the lower extremity. Advanced femoral nerve blocks can decrease the risk of deep venous thrombosis of the lower extremity after knee arthroplasty, but their mechanism of action remains unclear. We assume that the femoral nerve block can effectively suppress the inflammatory reaction and prevent deep venous thrombosis of the lower extremity after knee arthroplasty. Methods/Design: A total of 120 patients undergoing total knee arthroplasty under general anesthesia in the General Hospital of Ningxia Medical University of China will be enrolled in this single-center randomized controlled trial. These patients will be equally and randomly assigned to three groups. In the advanced femoral nerve block group, ultrasound-guided femoral nerve block will be conducted 30 minutes before surgery. In the conventional femoral nerve block group, ultrasound-guided femoral nerve block will be carried out at consciousness after surgery. In the intravenous analgesia group, an analgesia pump will be used to relieve pain after surgery. The primary outcomes will be the changes in the levels of serum thrombosis-related inflammatory factors (neutrophil elastase, thrombin-antithrombin III complex, D-dimers, C-reactive protein, tumor necrosis factor-α, interleukin-1, interleukin-6, and interleukin-8) immediately after entering the operating room; 30 and 60 minutes after application of the tourniquet; 30 minutes after removal of the tourniquet; and 12, 24 and 48 hours after surgery. The secondary outcomes measures will be the Ramsay Sedation Scale score, visual analogue scale score, times until initial and complete effect of the block, muscle strength rating, blood loss, and color Doppler ultrasound examination results of the lower extremity veins. Discussion: We hope to identify the clinical advantages of advanced femoral nerve block for total knee arthroplasty and determine whether deep venous thrombosis of the lower extremity after knee arthroplasty can be prevented by inhibiting the release of abundant neutrophil elastase and suppressing the inflammatory reaction. Trial registration: ClinicalTrial.gov identifier: NCT02411097; registered on 20 March 2015. Ethical approval: Written approval for this project was obtained from the Ethics Committee of the General Hospital of Ningxia Medical University of China. All patients or their family members will be informed of the protocols and will provide written informed consent. Our study is in accordance with the guidelines of the Declaration of Helsinki, formulated by the World Medical Association.