Should the Dose of Recombinant Activated Factor VII Be Adjusted for Morbidly Obese Patients? Balancing Risk of Bleeding With Thrombosis

Abstract

This case report compared and contrasted calculations for dosing recombinant activated factor VII (rFVIIa) in a morbidly obese patient using estimation of blood volume rather than actual weight or ideal body weight (IBW). A specific case report in a morbidly obese, critically ill patient with new diagnosis of acquired hemophilia A (AHA) was presented. A 64-year-old morbidly obese patient with AHA required emergent surgery for perforated diverticulitis and peritonitis. The patient required bypass treatment with rFVIIa and was initially dosed based on actual weight of 167 kg (body mass index 61). The patient had a history of deep vein thrombosis and new onset of atrial fibrillation. Based on numerous risk factors for both bleeding and the potential for thromboembolism, the rFVIIa dose was adjusted based on calculations using adjusted body weight and blood volume principles, which decreased dosage by 40%, from 15 to 9 mg. With no active bleeding, rFVIIa dosage was adjusted and rotating thromboelastography testing was added to coagulation parameter monitoring. With this change in dosage, hemostasis was maintained and 132 mg of rFVIIa was saved over an 8-day treatment period. There is very limited literature to direct clinicians on rFVIIa dosing in morbidly obese patients. Since obesity is prevalent in all patient populations, clinicians should consider an estimation of blood volume as a means to dose rFVIIa. Adjusting the dose of rFVIIa to account for changes in blood volume is a physiologic target that should help balance the risk of underdosing using IBW and the risk of overdosing using actual body weight.