Heparin-induced Thrombocytopenia (HIT): Pathophysiology, Diagnosis andRecommendations for Clinical Practise in Anaesthesiology and Critical CareMedicine

Overview

decades, heparins have been used successfully for prophylaxis and treatment of thromboembolic complications. although heparin-inducedthrombocytopenia (HIT Type II) is a well-known adverse effect of heparin therapy, thromboembolic complications during heparin therapy are rarelydiagnosed exactly to be related to HIT. An immunologic cause of HIT by generation of multimodal immune complexes against a neo antigen of heparinand platelet factor 4 is equivocally accepted as the decisive pathophysiological mechanism. The incidence of HIT seems to be related to the type ofheparin (unfractioned/low molecular weight) or other underlying risks such as peripheral occlusive vessel disease. Mortality on complications resultingfrom HIT is reported to be about 20 – 30%. For diagnosis of HIT Type II, clinical observation and simultaneous laboratory testing are essential.Discontinuation of any heparin therapy is necessary, and other well controllable anticoagulation regimens have to be continued. The heparinoiddanaparoid-sodium and the thrombin inhibitor recombinant hirudin have been used successfully world-wide for treatment in many patients with HITType II including cardiopulmonary bypass surgery or renal replacement procedures. Furthermore, other therapeutical alternatives (e.g. immunoglobu-lins, prostaglandins) exist. Randomised controlled studies have to evaluate which drug has to be preferred in the future including risk/benefit ratio.The need of supplementary procedures (e.g. embolectomy) depends on the individual clinical status. The patients have to be informed in detail abouttheir underlying disease and further deleterious consequences of re-exposition with heparin. HIT should be recorded in an emergency certificate andthe national Committee on Drugs should be informed about this severe side effect of heparin thera

Key words:
heparin – thrombocytopenia – thrombosis – danaparoid-sodium – recombinant hirudin