[Heparin-induced thrombocytopenia]

Heparin induced thrombocytopenia is encountered in clinical practice as type I and type II. Heparin induced thrombocytopenia type II is one of the most serious complications of heparin treatment. Its incidence is between 0.5-5% of all patients treated with heparins. Contrary to type I which is most probably caused by simple interaction of heparin with platelets, in type II factors of the immune system are involved. The laboratory diagnosis is complicated and negative, in vitro tests do not rule out the diagnosis in vivo. The latter is assessed most frequently per exclusionem when there is a marked drop of platelets associated with the clinical picture of thrombotic complications. Heparin must then be immediately discontinued and at the same time usually alternative antithrombotic treatment is necessary. Low-molecular heparins are contraindicated by the majority of authors because of possible immunological cross reactions, and coumarins are also unsuitable as drugs of first choice because of their late onset of effect and initial drop of protein C. Ideal preparations are most probably direct thrombin inhibitors (recombinant hirudin and its analogues, oligopetides). Anti-thrombocyte drugs can be used, possibly the defibrination enzyme ancrode (Arwin).