The most common hemophilias are caused by genetic deficiencies of factor VIII (hemophilia A) or factor IX (hemophilia B).
Bleeding complications depend on the severity of the disease. Patients with severe disease (factor VIII or factor IX activity level <1%) experience spontaneous bleeds and difficult to control bleeding after trauma. Patients with moderate disease (1% to 5% factor activity level) may bleed spontaneously but more commonly bleed after trauma. Patients with mild disease (5% to 40% factor activity level) usually only bleed after trauma. Easy bruising, recurrent hemarthrosis, and muscle hematomas are the most common clinical manifestations. Central nervous system (CNS) bleeding accounts for the most common cause of death. Retroperitoneal, gastrointestinal (GI), and soft tissue bleeding can occur. Mucocutaneous bleeding (dental bleeding, epistaxis, GI tract bleeding, lungs bleeding) can occur, although this is rare. Neck hematomas may obstruct the airway. Unless there is another underlying disease, most patients with hemophilia do not have problems with minor cuts or abrasions. Almost all cases of hemophilia occur in men with women being genetic carriers of the disease. The unlikely exception occurs when a hemophiliac man reproduces with a woman who is a carrier of the hemophilia gene; hemophiliac females can result. Owing to spontaneous mutations and lyonization of the X chromosome women may develop varying degrees of decreased factor levels.
A rare form of hemophilia occurs when a person develops a spontaneous antibody to their intrinsic factor VIII. It is often (40%) associated with other conditions such as autoimmune diseases, cancers, certain drugs, the postpartum period. It usually happens in the sixth or seventh decade and affects men and women equally. Widespread purpura and internal bleeding are common with hemarthrosis less common.
Diagnosis and Differential
Clinically, it is impossible to differentiate between hemophilias A and B. Laboratory testing in patients with hemophilia most often shows a normal prothrombin time (PT), prolonged partial thromboplastin time (PTT), and a normal bleeding time. However, if greater than 30% to 40% of factor activity is present, the PTT may be normal. Specific factor assays may be used to differentiate between the types of hemophilia. Ten percent to 25% of patients with hemophilia A and 1% to 2% of patients with hemophilia B will develop an inhibitor, which is an antibody against the deficient factor. The presence of an inhibitor makes treatment more difficult, requiring alternative, pre-activated factors such as recombinant factor VIIa or factor eight inhibitor bypassing activity (FEIBA).
Emergency Department Care and Disposition
The mainstay of therapy is early factor replacement. Replacement factor products are listed in Table 135-1.
Determine the type of hemophilia and the presence or absence of inhibitor. See Table 135-2 for factor replacement guidelines. Factor replacement may need to be instituted before definitive imaging after head trauma and other life-threatening injuries. If an inhibitor is present, use therapy as outlined in Table 135-3.
Determine the desired factor activity level. Factor activity level determines how much factor replacement is required. Calculate the amount of factor needed using the patient's weight and the desired increase in factor:
Factor VIII required = (Target factor – Base line factor) × Weight (kg) × 0.5
Factor IX required = (Target factor – Base line factor)× Weight (kg)
For severe hemophilia, assume 0% intrinsic activity. The half-life of factor VIII is approximately 8 to 12 hours. For hemophilia B, the half-life of factor IX is approximately 16 to 24 hours.
Treat patients with undiagnosed bleeding disorders with fresh frozen plasma (FFP). FFP contains 1 unit of factor VIII/mL. Specific factor assays should guide further therapy.
Treat minor bleeding in patients with mild hemophilia A with desmopressin (DDAVP) 0.3 µg/kg IV over 15 to 30 minutes or DDAVP 150 µg single spray in each nostril (for children >5 years, DDAVP 150 µg single spray in one nostril). Very mild mucosal bleeding can also be treated with antifibrinolytic agents, ...