Introduction: Heparin-induced thrombocytopenia (HIT) type II, induced by heparin therapy, may lead to haemorrhagic and thrombotic complications which are potentially life threatening. The reported incidence in the literature varied from 0.2-31% . Because administration of low-molecular-weight heparins (LMWH) is now more frequent, this complication has also been reported in several cases after LMWH administration.
Case report: A male patient, 55 years old, with unstable angina pectoris, received 60 mg of enoxaparin eighteen days before coronary artery bypass surgery. On the day of surgery, platelets values were within normal ranges. Cardiac surgery was performed using cardiopulmonary bypass (CPB) and the patient received 300 U kg−1 of unfractionated heparin before cannulation. Eight hours after surgery, the platelet count had fallen to zero. Immediately the administration of LMWH and any other contact with heparin was stopped. The appearance of anti-platelet antibodies was confirmed with direct and indirect platelet microimmunoflouroscence test (PSIFT) made by Jackson ImmunoResearch Lab. Inc., Baltimore, USA, and both tests were highly positive. Platelets value was zero during the next 36 hours, then increased until the fifth day, when values reached 100 × 109L−1. By that time, the patient was without anticoagulation therapy, and did not develop any kind of thrombosis. Regular blood tests were performed throughout the stay in ICU. The patient was discharged from hospital on the tenth day after surgery.
Discussion: Although there is a relatively low incidence of HIT in the population, especially after LMWH usage, pre-surgery testing is strongly advocated for all patients who receive unfractionated or LMWH before surgery, to prevent serious and life-threatening complications during and after CPB. The use of alternative agents (lepirudin, danaparoid, argatroban, fondaparinux) are still not absolute substitutes for traditional heparin in patients undergoing CPB. Furthermore, lack of a specific antidote to return the activated clotting time to the normal range after CPB makes these agents insufficient for use for cardiac surgery. Delaying surgery and clearing the antibodies from the circulation is still the only safe procedure for these patients.
1 Warkentin TE, Levine MN, Hirsh J, et al. Heparin-induced thrombocytopenia in patients treated with low-molecular-weight heparin or unfractionated heparin. N Eng J Med