Effects of unfractionated heparin, low-molecular-weight heparin, and heparinoid on thromboelastographic assay of blood coagulation

Thromboelastography (TEG) has been used increasingly as an intraoperative h emostasis monitoring device. Low-molecular-weight heparins are given increa singly to reduce the development of antibodies against the heparin-platelet factor 4 complex, and heparinoids are given to patients who have developed the antibody. We studied the effect of unfractionated heparin, a low-molec ular-weight heparin (enoxaparin sodium [Lovenox]), and a heparinoid (danapa roid sodium [Orgaran]) on blood clotting assayed with TEG (TEG clotting) in vitro and the efficacy of protamine sulfate and heparinase for reversing t he effect. Heparin, enoxaparin, and danaparoid all caused a dose-dependent inhibition of TEG clotting of normal blood. Concentrations of enoxaparin an d danaparoid that totally inhibited TEG clotting only minimally prolonged t he activated partial thromboplastin time. While inhibition of TEG clotting by heparin and enoxaparin was reversed by protamine sulfate and heparinase, inhibition by danaparoid was reversed only by heparinase. Abnormal TEG clo tting was observed in patients receiving enoxaparin whose plasma level of t he drug was more than 0.1 antiXa U/mL. However; the degree of TEG abnormali ty did not always coincide with plasma levels of the drug.