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Ann Thorac Surg 1997;63:1513-1514
© 1997 The Society of Thoracic Surgeons
Department of Anesthesiology, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Blvd, Dallas, TX 75235-9068
To the Editor:
I read with great interest the article by Kochamba and colleagues [1] regarding intraoperative autotransfusion after cardiopulmonary bypass (CPB). As in many preceding studies, a hemostatic benefit was not demonstrated that could explain the observed reduction in blood loss. Postoperative platelet counts, prothrombin times, and hematocrits were similar in the two patient groups. Unfortunately, there was no laboratory evidence documenting that heparin rebound was evaluated or treated before fresh frozen plasma administration occurred, as mandated by the transfusion algorithm.
Like many clinicians, I have always been intrigued by the hemostatic benefit of autologously harvested blood reinfused after CPB. My colleagues and I [2] recently published an article that may, in part, help explain a poorly appreciated prohemostatic effect of autologous blood harvested preoperatively and then reinfused immediately after protamine administration following CPB.
In our investigation, after heparinization and before CPB, venous blood (average, 4.9 mL/kg) was removed via an indwelling internal jugular catheter into a preservative-free plastic transfer pack unit and stored without agitation at room temperature. This autologous whole blood was then reinfused after systemic protamine reversal of heparin. Blood samples for analysis were drawn immediately before and 5 minutes after completion of the reinfusion. Autologous blood reinfusion appeared to be significantly related to increased hemoglobin, hematocrit, platelet count, fibrinogen, plasminogen, and antiplasmin levels. The prothrombin time and activated partial thromboplastin times decreased significantly, whereas activated clotting times and d-dimer levels were unchanged. Significant increases occurred in the following thromboelastography parameters: maximum amplitude, amplitude 60 minutes after the maximum amplitude, and whole blood clot lysis index. Reaction time and coagulation time were not statistically different from control values.
It is my belief that additional investigations need to be carried out to further delineate the exact influence on the hemostatic mechanism of autologously harvested whole blood reinfusion after CPB. In our study, autologous blood administration appeared to modulate the activity of the fibrinolytic mechanism, as documented by alterations in biochemical markers of fibrinolytic activity, as well as thromboelastography. We observed significant increases in both A60 and whole blood clot lysis index (thromboelastographic markers indicating decreased fibrinolytic activity) after autologous blood reinfusion. Our preliminary findings suggest that autologous blood reinfusion may have beneficial effects on post-CPB fibrinolytic abnormalities. This improvement could result from an antifibrolytic activity of infused platelets (PAI-1) or, in part, to observed, although small increases in antiplasmin activity, even though the antiplasmin levels after reinfusion in our investigation remained below the normal range.
In conclusion, we thought that increases in the WBCLI, which may have occurred as a result of increases in circulating antiplasmin levels, suggested that augmented fibrinolysis, a known phenomenon in the post-CPB period, was partially inhibited as a result of autologous blood reinfusion. In my opinion, our preliminary results suggest that the ability of autologously harvested blood to modulate the fibrinolytic mechanism should be the focus of future studies evaluating the hemostatic effect of autologous blood reinfusion after CPB.
References
Regional Department of Cardiac Surgery, Los Angeles Kaiser Permanente Medical Center, 1526 N Edgemont St, Los Angeles, Ca 90027
To the Editor:
Doctor Whitten and colleagues' study confirms the clinical benefit of autologous blood harvesting before cardiopulmonary bypass. The precise mechanism of the improvement in hemostasis is unclear but may include a decreased fibrinolysis and the maintenance of intact platelet function postoperatively.
Our studies differed as to the volume of blood pooling before cardiopulmonary bypass (4.9 mL/kg versus 10 mL/kg). The benefits of further increasing the blood pooling volume and the safety of lower hemodilution are yet to be determined. Oxygen-carrying volume expanders may explore these limits in future studies.
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