Cardiopulmonary bypass for patients with previously documented heparin-induced platelet aggregation.

Heparin-dependent intravascular coagulation is a widely recognized syndrome in which heparin acts as a hapten for an antiplatelet antibody and causes accelerated intravascular thrombosis and thrombocytopenia that may culminate in organ loss, hemorrhagic diathesis, and even death. Diagnosis is made in vitro by observing heparin-stimulated aggregation of normal platelets suspended in the patient's platelet-poor plasma. Treatment consists of cessation of heparin and use of antiaggregating agents with or without warfarin sodium. Management of patients with prior heparin-dependent intravascular coagulation who require cardiopulmonary bypass has not been reported. We now have successfully managed three such patients and herein present guidelines for management. Each patient was undergoing heparin therapy and manifested hallmark heparin tachyphylaxis, thrombocytopenia, and increased thrombotic symptoms (further venous thrombosis after cardiac catheterization in two cases and exacerbation of unstable angina in the other). In vitro aggregation studies were abnormal. Heparin was stopped, and antiaggregative therapy was begun with good response in each instance. In vitro studies were done serially until the antiplatelet antibody reaction had vanished (usually 4 to 8 weeks), and coronary revascularization was then conducted with full heparinization. Further heparin exposure postoperatively was avoided. There was no perioperative evidence of intravascular thrombosis or bleeding diathesis, and in vitro heparin-dependent aggregation did not recur. We conclude that patients with previously documented heparin-dependent intravascular coagulation can safely sustain the massive heparin rechallenge of cardiopulmonary bypass, provided that in vitro aggregation has ceased and rechallenge therapy is not prolonged.