On completion of the chapter, the reader will be able to:
Describe the regulation of hemostasis and thrombosis.
Describe the pathophysiology and genetics of hemophilia and the expected bleeding manifestations based on severity level.
List complications of bleeding episodes from hemophilia.
Compare the advantages and disadvantages of plasma-derived versus recombinant factor concentrates.
Calculate an appropriate factor-concentrate dose, given a desired percent correction, for any given factor concentrate product.
Formulate treatment options for a patient with hemophilia A who is bleeding and has a high-titer inhibitor.
Compare and contrast on-demand versus prophylactic administration of factor concentrates.
Identify the hematologic disorders for which desmopressin is indicated and the known side effects.
Identify strategies to eradicate inhibitors in patients with hemophilia.
Determine the appropriate treatment regimen based on a patient’s von Willebrand variant.
The coagulation system is intricately balanced and designed to stop bleeding at the site of vascular injury through complex interactions between the vascular endothelium, platelets, procoagulant proteins, anticoagulant proteins, and fibrinolytic proteins. Hemostasis stops bleeding at the site of vascular injury through the formation of an impermeable platelet and fibrin plug. Three key mechanisms facilitate hemostasis including vascular constriction, primary platelet plug formation (primary hemostasis), and clot propagation through fibrin formation (secondary hemostasis). Derangements in this finely tuned system can lead to either bleeding or thrombosis. Bleeding disorders are the result of either a coagulation factor defect, a quantitative or qualitative platelet defect, or enhanced fibrinolytic activity. The complex system regulating hemostasis is described in the pathophysiology section of Chapter 9.
Secondary hemostasis facilitates propagation and stabilization of the initial platelet plug formed in primary hemostasis through the formation of fibrin on the activated platelet surface. This step is initiated via the tissue factor pathway and is vital for adequate hemostasis. Coagulation factors circulate as inactive precursors (zymogens). Activation of these coagulation proteins entails a cascading series of proteolytic reactions (...