General considerations

General considerations

1. One unit of PRBCs, which has a Hct of about 70% and a volume of about 250 mL, will usually increase the Hct by 2% to 3% or the Hb by 1 g/dL in the euvolemic adult once equilibration has taken place. In euvolemic children, PRBC volumes of 4 mL/kg will also increase the Hb by approximately 1 g/dL. PRBCs must be ABO compatible with the recipient.
2. One unit of platelets increases the platelet count by 5000 to 10,000/mm³. A usual platelet transfusion is 1 unit per 10 kg of body weight. If thrombocytopenia is caused by a destructive or consumptive process or if platelets are dysfunctional, platelet transfusions will be less efficacious (see Section I.B). Transfusion of ABO-compatible platelets is not obligatory, although they may provide a better posttransfusion platelet count. Single-donor or HLA-matched platelets may be required for patients refractory to platelet transfusion. A unit of single-donor platelets provides the equivalent of approximately six random donor units of platelets. Owing to inactivation at low temperatures, platelets should be stored at room temperature and never placed in a cooler or refrigerator.
3. FFP, which is stored in volumes of about 250 to 300 mL/U and administered at doses of 10 to 15 mL/kg, should increase plasma coagulation factors to 30% of normal, the minimum necessary for hemostasis (except for fibrinogen, of which 50% of the normal 200-400 mg/dL concentration is required). Fibrinogen levels increase by 1 mg/dL per mL of plasma transfused. Acute reversal of warfarin is often achieved with only 5 to 8 mL/kg of FFP, although the PT may remain modestly prolonged. FFP transfusions must be ABO compatible, but Rh compatibility and cross-matching are not required (Table 36.1).
4. Cryoprecipitate is prepared via centrifugation of the plasma and contains concentrated factor VIII, factor XIII, fibrinogen, von Willebrand factor (vWF), and fibronectin. Indications for cryoprecipitate include hypofibrinogenemia, von Willebrand disease, hemophilia A (when recombinant factor VIII is unavailable), and preparation of fibrin glue. The usual dosage of 1 unit per 7 to 10 kg should raise the plasma fibrinogen by about 50 mg/dL in a patient without massive bleeding. ABO compatibility is not mandatory for cryoprecipitate transfusion.