Seminars in thrombosis and hemostasis
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Semin. Thromb. Hemost. · Jan 1995
Review Comparative StudyThromboelastography and cardiopulmonary bypass.
The TEG tracks postoperative hemorrhage after CPB and is useful in guiding therapy. Its ability to characterize the overall interaction of all procoagulant participants in a final outcome (clot strength) is unique. Much work in the future is needed to establish the particular applications for TEG monitoring in CPB patients
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The knowledge of these sources of error together with strict methodology assure reliable results and avoid what some authors consider limitations of the test. These so-called limitations are actually due to incomplete information or insufficient experience. It is our opinion that the key for success when using TEG is to use the test in those cases for which it has been indicated. ⋯ According to this review, the established applications of TEG are as follows: (1) detection of hypercoagulable states, particularly in the postoperative period and for patients with malignancies; (2) management of patients who are administered intravenous heparin; (3) monitoring the coagulation state during liver transplantation; (4) monitoring the coagulation state and management of patients during cardiopulmonary bypass; and (5) diagnosis and treatment of hematologic dysfunctions, particularly hemophilia. Management of patients under warfarin administration, as well as monitoring of the adjustment of subcutaneous heparin prophylaxis in several surgical procedures, should probably belong to this list, but further studies are needed to confirm these roles. Used by experienced hands, TEG is a valuable hemostatic test, the future of which is already present.
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The historical term "hemorrhagic disease of the newborn," which is used as a synonym for vitamin K deficiency bleeding (VKDB) in infancy, preferably should be abandoned, since neonatal bleeding is often not due to vitamin K (VK) deficiency and VKDB may occur after the neonatal period. VKDB is a form of bleeding that is caused by reduced activity of VK-dependent coagulation factors (II, VII, IX, X), has normal or even increased activity of VK-independent coagulation factors, and responds to VK. Acarboxy proteins are present. ⋯ Repeated (daily or weekly) oral doses of VK are closer to physiologic conditions than single parenteral bolus doses, which expose neonates to excessively high VK levels. The incidence of intracranial VKDB can be reduced if the grave significance of warning signs is recognized (icterus, failure to thrive, feeding problems, minor, bleeding, diseases with cholestasis) or if a simple test for acarboxy proteins (similar to the Guthrie test) would be applicable. Whether or not the more reliable absorption of the new mixed micellar preparation of VK could reduce the protective oral dose of VK prophylaxis has to be evaluated.
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The contribution of platelet dysfunction to the impaired hemostasis after cardiac surgery remains to be established, because there is no sensitive method to assess platelet function. Measurement of the shear-induced pathway of platelet function, an important mechanism in inducing hemostasis, became possible by a novel shear-inducing technique, the in-vitro bleeding test (Thrombostat 4000). By using this test, the changes in platelet function during cardiopulmonary bypass and their contribution to hemostasis were investigated in patients undergoing cardiac surgery. ⋯ These results indicate the significant and variable effects of cardiopulmonary bypass on the shear-induced pathway of platelet function. Moreover, the impairment of this function of platelets appears to be a major cause of excessive bleeding in patients after cardiac surgery. Therefore, the routine use of the shear-inducing test seems helpful to make a proper diagnosis and design the therapy for bleeders after cardiac surgery.
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TEG has played an integral part in the growth of liver transplantation. The group at the University of Pittsburgh early on realized that coagulation dysfunction during liver transplantation would be both severe and dynamic. Each phase of the operation appears to have both predictable and unexpected changes in clot dynamics. ⋯ What effect these new medications will have on hemorrhage or thrombosis of vascular anastomoses is yet to be adequately explored. A new awareness appears to be arriving that normal or excessively hypercoagulable states could contribute to such thromboses. TEG as a technology will certainly contribute to a number of future studies and clinical care, which will enhance the conduct of liver transplantation in the future.