Use of danaparoid sodium (Orgaran) as an alternative to heparin sodium during cardiopulmonary bypass: a clinical evaluation of six cases

Heparin-induced thrombocytopenia (an overview)

Heparin induced thrombocytopenia is a serious side effect of a drug that is widely used in clinical practice. All patients exposed to heparin, administered by any route or at any dose, are at varying risk of developing HIT and its potentially devastating thrombotic complications. There are two clinical forms of HIT, type I and type II. Type I HIT, is a non-immunologic response, while type II HIT is an immunologic response to heparin therapy. Type I HIT is not associated with an increased risk of thrombosis and is characterized by reversible thrombocytopenia. Type II HIT occurs in approximately 1 to 3% of patients receiving unfractionated heparin. Type II HIT is more severe because of the increased risk of thrombotic events. Venous and arterial thromboembolic complications may lead to amputation, stroke, myocardial infarction, and death.

The Management of Patients With Heparin-Induced Thrombocytopenia Who Require Anticoagulant Therapy

For patients with heparin-induced thrombocytopenia (HIT), reexposure to heparin is generally not recommended. However, these patients are likely to require anticoagulation therapy at some point in the future. During acute HIT, when thrombocytopenia and anti-heparin-platelet factor 4 antibodies (or HIT antibodies) are present, therapy with heparin must be avoided. In patients with subacute HIT, when platelets have recovered but HIT antibodies are still present, therapy with heparin should be avoided. In patients with a remote history of HIT, when HIT antibodies have cleared, heparin reexposure may be safe, although recurrent HIT has been described in some patients. For all of these patients, the use of alternate anticoagulant agents, including direct thrombin inhibitors and anti-Xa agents, is preferable. There is an increasing amount of data supporting the use of these alternative agents in a wide variety of clinical circumstances, including thromboprophylaxis and treatment of acute thrombosis. Except for a few clinical situations, it is generally possible to avoid heparin reexposure in patients with a history of HIT.

Alternatives to unfractionated heparin for anticoagulation in cardiopulmonary bypass

Despite the progress made in the development of cardiopulmonary bypass (CPB) equipment, systemic anticoagulation with unfractionated heparin and post-bypass neutralization with protamine are still used in most perfusion procedures. However, there are a number of situations where unfractionated heparin, protamine or both cannot be used for various reasons. Intolerance of protamine can be addressed with extracorporeal heparin removal devices, perfusion with (no) low systemic heparinization and, to some degree, by perfusion with alternative anticoagulants. Various alternative anticoagulation regimens have been used in cases of intolerance to unfractionated heparin, including extreme hemodilution, low molecular weight heparins, danaparoid, ancrod, r-hirudin, abciximab, tirofiban, argatroban and others. In the presence of heparin-induced thrombocytopenia (HIT) and thrombosis, the use of r-hirudin appears to be an acceptable solution which has been well studied. The main issue with r-hirudin is the difficulty in monitoring its activity during CPB, despite the fact that ecarin coagulation time assessment is now available. A more recent approach is based on selective blockage of platelet aggregation by means of monoclonal antibodies directed to GPIIb/IIIa receptors (abciximab) or the use of a GPIIb/IIIa inhibitor (tirofiban). An 80% blockage of the GPIIb/IIIa receptors and suppression of platelet aggregation to less than 20% allows the giving of unfractionated heparin and running CPB in a standard fashion despite HIT and thrombosis. Likewise, at the end of the procedure, unfractionated heparin is neutralized with protamine as usual and donor platelets are transfused if necessary. GPIIb/IIIa inhibitors are frequently used in interventional cardiology and, therefore, are available in most hospitals.