Individualizing Hemophilia Bypassing Agent Therapy Utilizing Thromboelastography

This pilot study will investigate the use of thromboelastograph (TEG) to determine the primary bypassing agent for the management of bleeding in children and adults severe hemophilia A patients with inhibitors. The study will evaluate the TEG profile for each of the available bypassing agents (FEIBA and rFVIIa) in each participating patient, which will then determine which agent provides the most robust clot formation as measured by the TEG. This study will consist of screening visit and 2-4 pharmacokinetic studies to determine the "best" bypassing agent based on the TEG results. Patients will then be assigned that bypassing agent and dose for the treatment of their bleeding episodes (Prophylaxis or On-demand). Each patient will be then followed for a period of 6 months to monitor short-term safety of those patients whose bypassing agent was modified.