Replacement therapy for hemophilia A Replacement therapy is currently the only effective treatment for bleeding in patients with hemophilia A. Treatment principles: 1. Timing of treatment: The earlier treatment is started for the patient, the better, preferably within 2h of the onset of symptoms, rather than waiting until signs appear. The earlier the treatment, the less painful the patient is, the less dose of coagulation factor products required, the faster the recovery and the lower the cost. Therefore, home treatment and self-injection should be actively encouraged to win valuable treatment time. 2. Clinical typing: The clinical typing of the patient must be fully understood before treatment (see previous article), and the typing is one of the bases for deciding the dosage of coagulation factor products. ①Severe bleeding, including bleeding from specific sites, such as central nervous system (intracranial) and soft airway (throat, neck) bleeding; gastrointestinal, urinary tract, respiratory tract bleeding; intraperitoneal/retroperitoneal bleeding and fundus bleeding. (ii) Moderate bleeding, including joint bleeding, muscle bleeding, oral bleeding, and soft tissue hematoma. ③Mild hemorrhage, including skin bruising, subcutaneous hematoma, nasal bleeding, etc. 3. FⅧ inhibitor: To know whether the patient has FⅧ inhibitor, FⅧ inhibitor test (commonly used Bethesda method) should be performed; FⅧ inhibitor titer <5 bioactive units (BU)/mL is low titer type, often without bleeding or with mild bleeding; FⅧ inhibitor titer ≥5BU/mL is high titer type, often with bleeding or severe bleeding. 4. Choice of blood products: Recombinant human activated FⅧ (rhFⅧ) products or plasma-derived FⅧ concentrates (anti-hemophilic globulin, AHG) are preferred; in the absence of the above products, cold precipitation or fresh frozen plasma (FFP) can be used; when patients have severe bleeding, rhFⅦa products (Nochi) can be used. 5. Experimental testing: In general, it is necessary to maintain the patient's plasma FⅧ:C level above the hemostasis level (20%-30%); maintain the APTT below 50-60s (reference range 31-43s); and maintain the FⅧ inhibitor titer at <5BU/mL.