Over the last few decades there has been an increased use of Warfarin in the pediatric population stemming from the use of mechanical heart valves and palliative surgical procedures requiring anticoagulation therapy. Other patients with enzymatic deficiency within the coagulation cascade may develop thrombosis treated with anticoagulation, i.e. factor V Leiden deficiency. Prevention of poor outcome from thrombosis has required closer monitoring in the pediatric patient. In addition, absorption of Warfarin in the pediatric population is highly variable and depends on the child's age, weight, diet, and concurrent use of other medications (Desai, 2000). This makes achieving anticoagulation very difficult. "Because of the intrinsic differences in the coagulation systems in children and adults, guidelines for antithrombotic therapy in adults cannot be extrapolated to pediatrics" (Desai, 2000). Therefore, pediatric patients on anticoagulation therapy require frequent lab work to monitor their prothrombin time and international ratios (PT/INR).