Antifibrinolytic Therapy Reduces Blood Loss in Knee Replacement Surgery

Abstract

We congratulate Zohar et al. (1) for their attempt to use tranexamic acid (TA) as a blood-saving strategy in orthopedic patients undergoing total knee replacement (TKR). The authors found TA has a superior blood-sparing effect as compared with that of acute normovolemic hemodilution (ANH). Nevertheless, ANH effectiveness depends on the intraoperative loss of erythrocyte-poor fluids and on retransfusion of the autologous blood, preferably at the end of surgery when no further blood loss is anticipated. Therefore, TKR is not an ideal model to demonstrate the effectiveness of ANH. When ANH is used as the sole blood conservation strategy, the acceptance of lower hemoglobin levels than considered in Zohar et al.’s (1) study parallels effectiveness (2,3). Furthermore, ANH patients generally need more fluids intraoperatively, and dilution remains present for 1 to 2 days or until fluid mobilization is facilitated by means of diuretics. This fact indicates that ANH patients are prone to reach a defined hemoglobin-transfusion trigger earlier. Using the formula of Gross (4) and considering even the lowest baseline hematocrit we are surprised that a cumulative blood loss of 639 mL in the ANH group versus 522 mL in the TA group resulted in postoperative hematocrit levels below 27% and did so more frequently in ANH patients. Is it possible that some of the ANH patients developed hematoma? These assumptions also arise because differences in blood loss of approximately 149 mL were present only during the 12-h TA administration, which in our opinion, seems not to be of clinical significance. Major orthopedic surgery strongly activates coagulation and fibrinolysis, and no differences occur, regardless of whether ANH is performed (5). When tourniquets are used, this secondary fibrinolysis is possibly more pronounced, and therefore, the use of TA is more effective than ANH. In our opinion, the results of the study primarily show that increased fibrinolytic activity is a relevant factor for blood loss in TKR, rather than ineffectiveness of ANH. Petra Innerhofer MD Gabriele Kühbacher MD Wolfgang Schobersberger MD