Anesth Analg 2000;91:497-498
© 2000 International Anesthesia Research Society
LETTERS TO THE EDITOR
Antifibrinolytic Therapy Reduces Blood Loss in Knee Replacement Surgery
Petra Innerhofer, MD,
Gabriele Kühbacher, MD, and
Wolfgang Schobersberger, MD
Department of Anesthesia and Intensive Care Medicine Leopold-Franzens University A-6020 Innsbruck, Austria
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.
References
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Zohar E, Fredman B, Ellis M, et al. A comparative study of the postoperative allogeneic blood-sparing effect of tranexamic acid versus acute normovolemic hemodilution after total knee replacement. Anest Analg 1999;89:1382–7.[Abstract/Free Full Text]
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Goodnough LT. Controversies in autologous blood procurement. Br J Anaesth 1998;81 (Suppl 1):67–72.
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Rottman G, Ness PM. Acute normovolemic hemodilution is a legitimate alternative to allogeneic blood transfusion. Transfusion 1998;38:477–9.[Web of Science][Medline]
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Gross JB. Estimating allowable blood loss: corrected for dilution. Anesthesiology 1983;58:277–80.[Web of Science][Medline]
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Hobisch-Hagen P, Wirnleiter B, Mair J, et al. Consequences of acute normovolaemic haemodilution on haemostasis during major orthopaedic surgery. Br J Anaesth 1999;82:503–9.[Abstract/Free Full Text]
Response
Edna Zohar, MD,
Brian Fredman, MB, BCh,
Martin Ellis, MB, BCh, and
Robert Jedeikin, MBChB, FFA(SA)
Department of Anesthesiology and Critical Care Meir Hospital Kfour Sava, Israel
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.
References
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Laks H, Handin RI, Martin V, Pilon RN. The effects of acute normovolemic hemodilution on coagulation and blood utilization in major surgery. J Surg Res 1976;20:225–30.[Web of Science][Medline]
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Gillon J, Thomas MJG, Desmong MJ. Acute normovolemic hemodilution. Transfusion 1996;36:640–3.[Web of Science][Medline]
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Olsfanger D, Fredman B, Goldstein B, et al. Acute normovolaemic haemodilution decreases postoperative allogeneic blood transfusion after total knee replacement. Br J Anaesth 1997;79:317–21.[Abstract/Free Full Text]
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Schmied H, Schiferer A, Sessler DI, Meznik C. The effect of red-cell scavenging, hemodilution, and active warming on allogenic blood requirements in patients undergoing hip or arthroplasty. Anesth Analg 1998;86:387–91.[Abstract]
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