Heparin and its biocompatibility.

Heparin has been used in clinical practice since 1936 as anticoagulant for: the treatment of thromboembolic disorders, the prevention of deep vein thrombosis and pulmonary embolism and the maintenance of blood fluidity in extracorporal circuits. Its use in these indications has been complicated by an increased risk of hemorrhage such as major bleeding during the treatment of pulmonary embolism and wound hematoma after surgery. Bleeding problems associated with the use of heparin in extracorporal circuits are the following: hemorrhages after cardiopulmonary bypass, serious hemorrhagic complications in patients treated with hemodialysis during acute renal failure and in patients on chronic intermittent hemodialysis and increased occult blood loss from the gastrointestinal tract and from other sites. The precise contribution of the use of heparin to the enhanced bleeding in these conditions has not yet been established. The effects on platelets, coagulation factors and/or fibrinolytic activity by the exposure of blood to foreign surfaces together with uremia present in hemodialysis patients may also contribute to abnormalities in clinical hemostasis. Recently heparin fractions and a heparinoid of low molecular weight (LMW) have been developed because of their potential to diminish the hazard of hemorrhage while retaining their antithrombotic properties. Preliminary reports from pilot studies have confirmed the increased efficacy in preventing deep vein thrombosis (DVT) of some of the new LMW heparin(oid)s; however, improved safety with regard to bleeding still needs to be shown. The use of LMW heparins and of a new LMW heparinoid in acute and chronic hemodialysis has also been shown to be effective.(ABSTRACT TRUNCATED AT 250 WORDS)