hematology and oncology
Thrombocytopenia: Other Causes
Heparin induced thrombocytopenia
 (eg, used in flushes to keep IV or arterial lines open) is used. The mechanism is usually immunologic. Bleeding rarely occurs, but more commonly platelets clump excessively, causing vessel obstruction, leading to paradoxical arterial and venous thromboses, which may be life threatening (eg, thromboembolic occlusion of limb arteries, Overview of Stroke , Heparinshould be stopped immediately in any patient who becomes thrombocytopenic and develops a new thrombosis or whose platelet count decreases by more than 50% pending results of tests done to detect antibodies toheparinbound to platelet factor 4. Anticoagulation with a nonheparin anticoagulant (eg,argatroban,bivalirudin,fondaparinux) should be substituted at least until platelet recovery. Low-molecular-weightheparin(LMWH) is less immunogenic than unfractionatedheparinbut cannot be used to anticoagulate patients withheparin-induced thrombocytopenia because most HIT antibodies cross-react with LMWH.Fondaparinuxis an acceptable alternative in many patients but given its long 17-hour half-life, is not appropriate in those patients who may soon need a procedure or have a high bleeding risk.Warfarinshould not be substituted forheparinin patients withheparin-induced thrombocytopenia, and if long-term anticoagulation is required.Warfarinshould be started only after the platelet count has recovered. 