Heparin induced thrombocytopenia in patients undergoing intra-aortic balloon pumping after open heart surgery.

Heparin is usually administered to patients with intra-aortic balloon pumps (IABP) to prevent thromboembolism. In addition to thrombocytopenia caused by IABP mechanical damage to platelets, exposure to heparin can cause heparin induced thrombocytopenia (HIT). Heparin induced thrombocytopenia is caused by an immune mechanism in which heparin antibodies are produced, causing platelet aggregation, leading to bleeding or thromboembolic complications. Over a 9 year period, 35 of 764 (4.5%) patients with IABPs have been diagnosed as having HIT. Surgical procedures included coronary artery bypass (CABG) in 14 (40%), valve repair or replacement in 7 (20%), and CABG and other cardiac procedure in 14 (40%). Lowest platelet counts ranged from 17,000-114,000/mm3 (median, 44,000/mm3). Thirty-three of 35 (94.3%) had mediastinal hemorrhage requiring infusion of multiple blood products, and 6 of these 35 (17%) required return to the operating room. Seventeen of 35 (48.6%) experienced thromboembolic complications. Hospital mortality was 15 of 35 (42%). Etiology of thrombocytopenia in patients on IABPs is multifactorial. Patients on an IABP who develop thrombocytopenia should be tested for heparin dependent anti-platelet antibodies to rule out HIT. When a heparin antibody is present, heparin must be discontinued and alternate forms of anticoagulation/platelet inhibition initiated to reduce morbidity and mortality.