A comparative study of the postoperative allogeneic blood-sparing effects of tranexamic acid and of desmopressin after total knee replacement

BACKGROUND: Tissue hypoxia and reperfusion induce abnormal hemostatic function. Therefore, bleeding after total knee replacement (TKR) may be a result of a tourniquet-induced imbalance of the procoagulant and fibrinolytic systems. Because laboratory confirmation of tourniquet-induced abnormal hemostasis is difficult to obtain, indirect evidence must be sought. STUDY DESIGN AND METHODS: A prospective, single-blind study of 40 patients undergoing TKR was performed. In the tranexamic acid (TA) group, in the 30 minutes before the limb tourniquet was deflated, an IV bolus dose of TA (15 mg/kg) was administered. Thereafter, a constant IV infusion of 10 mg per kg per hour was administered until 12 hours after tourniquet deflation. In the desmopressin group, desmopressin (0.3 mg/kg) and saline were administered by a similar protocol. No blood was administered intraoperatively. A postoperative Hct < 27 percent constituted the postoperative transfusion trigger. Patients were examined daily for signs of lower-limb deep vein thrombosis, and they underwent lower-limb Doppler ultrasound on postoperative Day 5. Three months after surgery, the incidence of delayed thromboembolic events was assessed. RESULTS: During the first 12 postoperative hours, blood accumulation in the surgical drain was significantly (p <0.05) lower in the TA group (162 mL +/- 129) than in the desmopressin group (342 mL +/- 169). From the sixth postoperative hour until 3 days postoperatively, Hct levels were significantly lower in the desmopressin group than in the TA group. Significantly more allogeneic blood was transfused in the desmopressin group (11 patients received 16 units) than in the TA group (3 patients each received 1 unit) (p <0.02). There were no clinical signs of deep vein thrombosis or abnormal Doppler ultrasound studies. Three months postoperatively, there were no thromboembolic events among the 37 patients interviewed. CONCLUSION: TA induces better blood sparing than desmopressin. Therefore, a tourniquet-induced increase in fibrinolysis is the likely cause of delayed bleeding after TKR surgery. However, before routine administration, the effect of TA on the incidence of thromboembolic events requires further investigation.