[Thrombocytopenia induced by heparin. Diagnosis, treatment, physiopathology: current concepts].

Iatrogenic thrombocytopenia is a rare, but severe complication of treatments with heparin and heparinoids. Mean temporary thrombocytopenia failing to show any complications are usually diagnosed as quite different from acute and delayed thrombocytopenia of which severity depends mainly on thrombotic symptoms demonstrated in 65 p. 100 of cases; the initial evolution of an average thrombocytopenia is not easy to diagnose; it may as well exist a connection between the two diseases, from a physiopathogenic point of view. The diagnosis of severe thrombocytopenia depends:--clinically, on the initial data, delayed as compared with the heparin treatment beginning and existence of arterial and/or venous thrombosis;--biologically, by demonstrating an aggregating activity for platelets in presence of heparin, in the patient plasma. Such an activity requires the suppression of standard heparinotherapy as well as the choice of substitutive anticoagulant treatment in case of evolutive thrombosis. Low molecular weight heparins are prescribed only if in vitro tests of platelet aggregation with the patient's plasma are negative. Antivitamins K are to be used as soon as possible alone or combined with heparin fractions. Antiaggregants are prescribed alone, above all in case of isolated thrombocytopenia and combined with AVK. Treatment of thrombotic complications depends on surgical disobstruction if arterial thrombosis, and use of fibrinolytics if pulmonary embolisms. The acute reaction of some thrombocytopenia to heparin as well as therapeutic difficulties demonstrate the efficiency of an early diagnosis performed thanks to systematic platelet numerations during the first 15 days of a treatment with heparin, as well as to the prevention along with systematic association with aspirin, especially if replaced with AVK.