tailieunhanh - Chapter 110. Coagulation Disorders (Part 4)

Chapter 110. Coagulation Disorders (Part 4) Factor VIII and Factor IX are dosed in units. One unit is by definition the amount of FVIII (100 ng/mL) or FIX (5 µg/mL) in 1 mL of normal plasma. One unit of FVIII per kilogram of body weight increases the plasma FVIII level by 2%. One can calculate the dose needed to increase FVIII levels to 100% in a 70-kg severe hemophilia patient ( | Chapter 110. Coagulation Disorders Part 4 Factor VIII and Factor IX are dosed in units. One unit is by definition the amount of FVIII 100 ng mL or FIX 5 iig mf in 1 mL of normal plasma. One unit of FVIII per kilogram of body weight increases the plasma FVIII level by 2 . One can calculate the dose needed to increase FVIII levels to 100 in a 70-kg severe hemophilia patient 1 using the simple formula below. Thus 3500 units of FVIII will raise the circulating level to 100 . FVIII dose IU Target FVIII levels - FVIII baseline levels x body weight kg x unit kg The doses for FIX replacement are different from those for FVIII because FIX recovery postinfusion is usually only 50 of the predicted value. Therefore the formula for FIX replacement is FIX dose IU Target FIX levels - FIX baseline levels x body weight kg x unit kg The FVIII half-life of 8-12 h requires injections twice a day to maintain therapeutic levels whereas the FIX half-life is longer 24 h so that once-a-day injection is sufficient. In specific situations such as postsurgery continuous infusion of factor may be desirable because of its safety in achieving sustained factor levels at a lower total cost. Cryoprecipitate is enriched with FVIII protein each bag contains 80 IU of FVIII and was commonly used for the treatment of hemophilia A decades ago it is still in use in some developing countries but because of the risk of bloodborne diseases this product should be avoided in hemophilia patients when factor concentrates are available. Mild bleeds such as uncomplicated hemarthroses or superficial hematomas require initial therapy with factor levels of 30-50 . Additional doses to maintain levels of 15-25 for 2 or 3 days are indicated for severe hemarthroses especially when these episodes affect the target joint. Large hematomas or bleeds into deep muscles require factor levels of 50 or even higher if the clinical symptoms do not improve and factor replacement may be required for a period of 1 week or .