ABSTRACT

INTRODUCTION Immediate cessation of, and avoidance of reexposure to, heparin are important principles underlying the management of patients with immune-mediated heparininduced thrombocytopenia (HIT) (Chong and Berndt, 1989). Because further antithrombotic therapy is often necessary for these patients, several alternative anticoagulant strategies have been developed (see chaps. 12-17). However, patients with HIT who require cardiac surgery present exceptional problems. Apart from the inherent disturbances of the hemostatic system in this patient population, considerable activation of the hemostatic system results from the surgical trauma itself. Furthermore, during cardiopulmonary bypass (CPB), there is exposure of blood to the large nonendothelial surfaces of the CPB circuit and reinfusion of tissue factoractivated blood aspirated from the operative fi eld into the CPB system. This profound hemostatic activation requires potent high-dose anticoagulation to prevent thrombosis within both the CPB system and the patient (Edmunds, 1993; Slaughter et al., 1994). Anticoagulation with unfractionated heparin (UFH), point-of-care monitoring by activated clotting time (ACT) systems, and reversal via the antidote protamine comprise a long-standing and well-established strategy permitting cardiac surgery. This approach is so universally entrenched that there is very minor experience with all other forms of anticoagulation in this patient setting.