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

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.