Antifibrinolytic Therapy Reduces Blood Loss in Knee Replacement Surgery

Abstract

Because the mechanism of hemodilution-induced allogeneic blood sparing is poorly understood, the efficacy of normovolemic hemodilution (NVHD) is controversial. As stated in our article, the blood-sparing effect of NVHD is likely multifactorial. First, because NVHD decreases hematocrit, blood with a low red cell mass is lost in the extravascular compartment. Second, it has been postulated that hemodilution results in improved blood flow in the microcirculation and thus decreases coagulopathies and postoperative bleeding (1,2). Third, fresh autologous blood has preserved platelets and clotting factors. Because total knee replacement (TKR) is associated with extensive postoperative blood loss (which is not controlled by surgical techniques), transfusing blood that is rich in platelets and clotting factors has the theoretical potential to decrease postoperative bleeding and allogeneic blood requirements. Finally, when compared with control, NVHD has been shown to significantly reduce allogeneic blood transfusion after TKR (3,4). Therefore, we disagree with the authors’ comment that acute normovolemic hemodilution (ANH) is not an appropriate technique for TKR. We agree that the current literature supports the comment that the acceptance of lower hemoglobin levels parallels the efficacy of NVHD as a blood sparing strategy. However, although hemodilution has been shown to be well tolerated in elderly patients with no known cardiac disease, undiagnosed disease is not uncommon in geriatric patients undergoing TKR. Therefore, to avoid the unwanted complications associated with hemodynamic instability, a transfusion hematocrit of 27% was preferred. The cumulative 24-h blood loss in our study was 391 vs 209 mL for the NVHD and TA groups, respectively (and not 639 vs 522 mL/24 h as stated in Innerhofer et al.’s letter). As explained in our article, to decrease the risk of infection, surgical drains were removed 24 h postoperatively. However, our hematocrit data suggest that covert bleeding continues during the subsequent recovery period. In our study, fibrinolysis was not investigated. Therefore, we do not accept the authors’ conclusion that “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.” Because the aim of our study was to compare the relative efficacy of two allogenic blood sparing strategies, we conclude that tranexamic acid administration is associated with superior allogeneic blood sparing when compared with NVHD. Edna Zohar MD Brian Fredman MB, BCh Martin Ellis MB, BCh Robert Jedeikin MBChB, FFA(SA)