Does Thinning the Blood During Surgery Prevent Blood Clots Following Total Knee Replacement Surgery

• DVT as determined by venography [ Time Frame: 5 day post op ] [ Designated as safety issue: No ]
  

• Bleeding rate Rate of PE Complication Rate [ Time Frame: 2 week post op ] [ Designated as safety issue: No ]
  

Drug: unfractionated heparin
Five minutes prior to tourniquet inflation, patients will receive 0.1 ml/kg/minute of intravenous (IV) unfractionated heparin (1000 units/ml) or placebo (normal saline solution). Five minutes will be allowed to elapse to ensure complete systemic heparinization. The operated limb will then be elevated and exsanguinated using an Esmarch bandage. Following cuff inflation, the contents of a second syringe will be administered IV over a 5 minute period. The second syringe will contain either protamine sulfate (1.0 mg/kg) to reverse the systemic heparin for patients in the treatment group, or normal saline for the control group. Study drugs will be administered by the anaesthesiologist via a peripheral IV. This new method of intraoperative regional heparinization has been used in two previous studies (Giachino et al., 2001; Giachino et al., 1985) with no adverse effects noted.

Venous thromboembolism is a major cause of morbidity and mortality after lower limb orthopaedic surgery in the adult patient. If, as suggested, DVT formation begins intra-operatively then targeting this period to prevent clot formation could substantially reduce DVT rates in the TKA population. The present study aims to determine whether this intra-operative regional heparinization technique is effective in preventing the intra-operative formation of DVT following TKA, as evidenced by venography in the early post-operative period.