Heparin-induced thrombocytopenia: a prospective study.

Thrombocytopenia is a well-described complication of heparin therapy. Few studies describe the incidence of thrombocytopenia when low-dose heparin (10,000-15,000 units/day) is used for prophylaxis of deep venous thrombosis. In our study, ten of 66 courses (15%) of heparin prophylaxis in coronary care unit patients were accompanied by a mild thrombocytopenia with platelet counts below 150 X 10(3)/mm3. In all cases the platelet count returned to normal despite continued heparin therapy. Patients who became thrombocytopenic had significantly lower initial platelet counts. No cases of severe thrombocytopenia were seen (platelet count below 100 X 10(3)/mm3). No patient developed thrombosis, bleeding or elevated fibrin split products. Mild thrombocytopenia occurring after 2-5 days of low-dose heparin is common, but clinically insignificant.