Prevention of venous thromboembolism in medical patients with thrombocytopenia or with platelet dysfunction: a review of the literature.

Current guidelines for venous thromboembolism (VTE) primary prophylaxis are based on randomized clinical trials that exclude subjects at a potentially high bleeding risk. Thus no specific recommendation/algorithm for pharmacological prophylaxis in patients with thrombocytopenia and/or platelet dysfunction is available. Because at least 25% of subjects admitted to medical departments exhibit these conditions, information on this subject is provided here to optimize their VTE prophylaxis. Low platelet number/function and clotting abnormalities are common in patients with liver cirrhosis. However, these patients have a high incidence of portal and idiopathic venous thromboses, implying that cirrhotic coagulopathy does not protect against thrombosis. At variance with severe thrombocytopenia (< 50,000/μL), mild/moderate thrombocytopenia (> 50,000/μL) should not interfere with VTE prevention decisions. In severe thrombocytopenia, prophylaxis should be considered on an individual basis, however. In patients with antiphospholipid antibodies and thrombocytopenia, a thrombotic tendency is usually associated rather than a bleeding risk. VTE prophylaxis in high-risk conditions is thus suggested in these patients. Except in cases with contraindications to anticoagulation, antithrombotic prophylaxis should be always considered in hospitalized cancer patients with thrombocytopenia, especially in those with hematologic malignancies and multiple VTE risk factors. Aspirin treatment is not as effective as heparins in lowering the risk of VTE. Studies in stroke suggest that thromboprophylaxis with heparins is safe in patients with ischemic stroke undergoing aspirin treatment. The need for VTE prophylaxis in patients on chronic treatment with aspirin and/or clopidogrel should be evaluated after assessing the individual risk-benefit ratio.