Recombinant Factor VIIa: The Possibilities for Monitoring

Comprehensive care of the patient with haemophilia and inhibitors undergoing surgery: practical aspects

Congenital haemophilia is a rare and complex condition for which dedicated specialized and comprehensive care has produced measurable improvements in clinical outcomes and advances in patient management. Among these advances is the ability to safely perform surgery in patients with inhibitor antibodies to factors VIII and IX, in whom all but the most necessary of surgeries were once avoided due to the risk for uncontrollable bleeding due to ineffectiveness of replacement therapy. Nevertheless, surgery continues to pose a major challenge in this relatively rare group of patients because of significantly higher costs than in patients without inhibitors, as well as a high risk for bleeding and other complications. Because of the concentration of expertise and experience, it is recommended that any surgery in patients with haemophilia and inhibitors be planned in conjunction with a haemophilia treatment centre (HTC) and performed in a hospital that incorporates a HTC. Coordinated, standard pre-, intra- and postoperative assessments and planning are intended to optimize surgical outcome and utilization of resources, including costly factor concentrates and other haemostatic agents, while minimizing the risk for bleeding and other adverse consequences both during and after surgery. This article will review the special considerations for patients with inhibitors as they prepare for and move through surgery and recovery, with an emphasis on the roles and responsibilities of individual members of the multidisciplinary team in facilitating this process.

Mechanisms and monitoring of bypassing agent therapy

Understanding the mechanism of action of normal hemostasis and how the bypassing agents recombinant activated factor VII (rFVIIa; NovoSeven) and plasma-derived activated prothrombin complex concentrate (Factor Eight Inhibitor Bypassing Agent [FEIBA]) control abnormal bleeding is imperative for healthcare professionals who treat patients with hemophilia and other bleeding disorders. A cell-based model has improved our understanding of in vivo mechanisms of hemostasis and the basis of the bleeding tendency in hemophilia. Bypassing agents do not restore the normal pathways of hemostasis in hemophilia, but rather boost thrombin generation in spite of a lack of platelet surface FVIIIa-FIXa ('tenase') activity. Thus, the common clinical laboratory coagulation assays do not reflect the clinically relevant hemostatic activity of bypassing agents, and no validated assay is available with which to measure the in vivo efficacy of these agents or predict individual patient responses to treatment. Global hemostasis assays measuring overall coagulation capacity have potential for assessment of the effects of bypassing agents. This review will focus on the mechanisms of clotting and their relationship to understanding the mechanisms of action of the bypassing agents in vivo and the methodologies that are emerging to monitor the clinical efficacy of bypassing agent therapy.