refludan and Gangrene

Recommendations for transitioning from therapy with heparin or a low-molecular-weight heparin preparation to therapy with an oral anticoagulant in patients with acute venous or arterial thromboembolism have undergone several changes during the last two decades. Physicians are now comfortable with beginning treatment with an oral anticoagulant once the diagnosis is confirmed, and loading doses are no longer considered to be necessary. Exceptions to early transition may be necessary in patients with an extensive iliofemoral or axillary-subclavian vein thrombosis or pulmonary embolism where thrombolytic agents may be indicated, or in individuals who require surgery or other invasive procedures, or if there are concerns about bleeding. The avoidance of early transition to oral anticoagulants in patients with acute heparin-induced thrombocytopenia also has been advised because of the potential for further thrombotic complications, including venous limb gangrene and warfarin-induced skin necrosis.

Topics: Administration, Oral; Anticoagulants; Arginine; Blood Coagulation; Blood Coagulation Factors; Chondroitin Sulfates; Dermatan Sulfate; Drug Combinations; Gangrene; Heparin; Heparitin Sulfate; Hirudins; Humans; Ischemia; Leg; Necrosis; Pipecolic Acids; Recombinant Proteins; Skin; Sulfonamides; Thrombocytopenia; Thrombosis; Warfarin

The past decade has seen many important advances in the pathogenesis, clinical and laboratory diagnosis, and management of heparin-induced thrombocytopenia (HIT), one of the most common immune-mediated adverse drug reactions. HIT is caused by IgG antibodies that recognize complexes of heparin and platelet factor 4, leading to platelet activation via platelet Fc gamma IIa receptors. Formation of procoagulant, platelet-derived microparticles, and, possibly, activation of endothelium generate thrombin in vivo. Thrombin generation helps to explain the strong association between HIT and thrombosis, including the newly recognized syndrome of warfarin-induced venous limb gangrene. This syndrome occurs when acquired protein C deficiency during warfarin treatment of HIT and deep venous thrombosis leads to the inability to regulate thrombin generation in the microvasculature. The central role of HIT antibodies in causing HIT, as well as refinements in laboratory assays to detect these antibodies, means that HIT should be considered a clinicopathologic syndrome. The diagnosis can be made confidently when one or more typical clinical events (most frequently, thrombocytopenia with or without thrombosis) occur in a patient with detectable HIT antibodies. The central role of thrombin generation in this syndrome provides a rationale for the use of anticoagulants that reduce thrombin generation (danaparoid) or inhibit thrombin (lepirudin).

Topics: Antibodies; Anticoagulants; Antithrombin III; Chondroitin Sulfates; Dermatan Sulfate; Drug Combinations; Fibrinolytic Agents; Gangrene; Heparin; Heparinoids; Heparitin Sulfate; Hirudin Therapy; Hirudins; Humans; Immunoglobulin G; Leg; Platelet Activation; Platelet Factor 4; Protein C Deficiency; Receptors, IgG; Recombinant Proteins; Retrospective Studies; Syndrome; Thrombin; Thrombocytopenia; Venous Thrombosis; Warfarin

Heparin-induced thrombocytopenia (HIT) may be complicated by severe thrombotic complications and death. Currently no specific laboratory test is available to make the diagnosis. When HIT is clinically suspected, heparin should be discontinued immediately. While no specific therapy for HIT exists, there is increasing evidence that acute antithrombin therapy may significantly reduce morbidity and mortality. Among several agents, the direct antithrombins, such as r-hirudin and argatroban, look the most promising for acute treatment.

Topics: Ancrod; Arginine; Chondroitin Sulfates; Dermatan Sulfate; Drug Combinations; Fibrinolytic Agents; Forecasting; Gangrene; Hemorrhage; Heparin; Heparitin Sulfate; Hirudin Therapy; Hirudins; Humans; Pipecolic Acids; Platelet Aggregation; Protein C; Recombinant Proteins; Sulfonamides; Thrombin; Thrombocytopenia; Warfarin

We report two patients with deep-vein thrombosis complicating immune heparin-induced thrombocytopenia who developed venous limb gangrene during overlapping therapy with a direct thrombin inhibitor (lepirudin or argatroban) and warfarin. In both patients, therapy with the direct thrombin inhibitor was interrupted during persisting severe athrombocytopenia while warfarin administration continued. Both patients exhibited the typical feature of a supratherapeutic international normalized ratio (INRs, 5.9 and 7.3) that has been linked previously with warfarin-associated venous limb gangrene. These data suggest that warfarin anticoagulation be postponed in patients with acute heparin-induced thrombocytopenia until substantial recovery of the platelet count has occurred.

Topics: Aged; Aged, 80 and over; Amputation, Surgical; Anticoagulants; Arginine; Autoimmune Diseases; Catheterization, Central Venous; Contraindications; Drug Administration Schedule; Drug Therapy, Combination; Female; Gangrene; Heparin; Hirudin Therapy; Hirudins; Humans; International Normalized Ratio; Leg; Male; Middle Aged; Necrosis; Pipecolic Acids; Protein C Deficiency; Recombinant Proteins; Sulfonamides; Surgical Wound Infection; Thrombin; Thrombocytopenia; Thrombophlebitis; Warfarin