PERIOPERATIVE ANTICOAGULATION AND THROMBOLYSIS IN CONGENITAL AND ACQUIRED COAGULOPATHIES

Abstract

Patients with congenital or acquired coagulopathies are undergoing increasingly complex operations that may require anticoagulation. Using large doses of heparin in patients with hemophilia during coronary artery bypass surgery without first correcting the underlying coagulation deficit may have catastrophic consequences. Before 1965, mortality for hemophiliacs undergoing general surgical procedures ranged from 13% to 67%. Over the last 30 years, operations on patients with hemophilia and other coagulopathies have been performed with low morbidity and mortality results, primarily because of improved laboratory testing, perioperative administration of coagulation factors to bring the missing factor activity to normal, and close perioperative follow-up to evaluate and further correct hemostatic protein activity. 200 To prepare these patients properly for surgery, complex diagnostic tests and specific therapies are required preoperatively because diagnosis and treatment during the surgery may be difficult or impossible, with severe consequences for the patient. As the perioperative use of anticoagulants in patients with congenital coagulopathies is becoming safe and routine, physicians are becoming aware of other acquired coagulation disorders such as heparin-induced thrombocytopenia. Heparin-induced thrombocytopenia has special clinical significance because heparin is still the first-choice treatment for the systemic anticoagulation required for certain cardiac and vascular surgeries. Finding that it was contraindicated in some patients stimulated intense research for alternatives, which produced heparin substitutes such as heparinoids, low molecular weight heparins (LMWHs), direct thrombin inhibitors, and glycoprotein IIb/IIIa receptor inhibitors. The expansion of knowledge about the coagulation and anticoagulation mechanisms over the last several decades has also brought a better understanding of some of the thrombotic phenomena that anesthesiologists and surgeons encounter in their daily practice. The increased incidence of thrombosis in some segments of the population is now known not to be simple “bad luck,” but rather to be the result of underlying pathologies of the coagulation cascade, most commonly protein C, protein S, and antithrombin III deficiencies. In 1993, investigators in Sweden 38 and the Netherlands 111 described a new defect in the hemostatic pathway, called resistance to activated protein C. This disorder occurs in 4% to 6% of the US population, making them especially prone to thromboembolic events during the perioperative period, pregnancy, or oral contraceptive use. Antiphospholipid antibodies may also cause a hypercoagulable state. Taylor et al 194 demonstrated that antiphospholipid antibodies are present in 25.6% of patients undergoing peripheral vascular surgery. This patient population may require not only short-term perioperative thrombotic prophylaxis but also long-term prophylaxis. However, dosage and duration of anticoagulant therapy for some of the hypercoagulable states is still not fully defined. In this article, we describe the pathophysiology of the most common hyper- and hypocoagulable disorders and discuss the impact of perioperative use of anticoagulants and thrombolytics in patients with these conditions.