In vitro analysis of shed blood from patients undergoing total knee replacement surgery

One method used to obtain autologous blood includes collection of wound drainage postoperatively. The decision to wash wound drainage before infusion is left to individual institutions. The composition of blood collected from joint spaces has not been adequately evaluated. Wound drainage from total knee replacement was collected into a cardiotomy reservoir, without anticoagulation, for 4 hours after surgery. Coagulation parameters were evaluated on the washed supernatant and unwashed supernatant. The most significant findings were the following: 1. Modified prothrombin time: washed supernatant and unwashed supernatant were substituted for tissue thromboplastin reagent. The unwashed supernatant initiated fibrin formation (mean, 108 seconds), whereas the washed supernatant did not (mean, > 150 seconds, P = .01). 2. Euglobulin lysis times: Mixtures containing 50% normal plasma and 50% washed supernatant or unwashed supernatant were used to determine plasmin activation (unwashed supernatant + normal plasma = 24 minutes; washed supernatant + normal plasma = 106 minutes; P = .03). Lower euglobulin lysis times indicates increased plasmin activity. 3. Fibrin degradation products: Concentrations were significantly elevated in unwashed supernatant (mean 10,240 micrograms/mL) versus washed supernatant (mean 5 micrograms/mL, P = .02). Fibrin degradation products are inhibitors of fibrin formation and platelets. The authors conclude the unwashed supernatant from wound drainage collected after total knee replacement contains activated components of the soluble coagulation and fibrinolytic systems, and these substances can be significantly reduced with washing.