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Information

  1. 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.
  2. Technical considerations
    1. Compatible infusions. Blood products should not be infused with hypotonic (eg, 5% dextrose) solutions, as these may cause hemolysis. Recent studies have suggested that coinfusion with calcium-containing lactated Ringer’s solution may not induce clot formation, but concern persists. Coadministration of blood products with Plasmalyte solutions is probably safe. Normal saline (0.9%) solution, albumin (5%), and FFP are compatible with RBCs and may be preferred in diluting blood products or priming blood delivery systems.
    2. Blood filters. Standard blood filters (170-200 μm) remove debris and should be used for all blood components. However, manufacturer recommendations for specific bedside blood filters should be followed with respect to the component to be filtered and the number of units administered per filter.
      1. Leukocyte reduction (leukoreduction) is achieved by filtration, either in the blood bank or at the bedside. Microaggregate filters (20-50 μm), which should not be used for platelets, remove 70% to 90% of leukocytes. Third-generation or adhesion filters remove more than 99.9% of leukocytes via a combination of filtration and adhesion of white blood cells. These filters are recommended for use in patients with a history of febrile nonhemolytic transfusion reactions, for prevention of alloimmunization to foreign leukocyte antigens (eg, in the oncologic patient expected to require multiple platelet transfusions), or to prevent cytomegalovirus (CMV) transmission in organ transplant recipients. Other potential but unproven benefits of leukocyte reduction include a diminished immunomodulatory effect of allogeneic transfusion; reduced transmission of bacterial, viral, or prion diseases; prevention of transfusion-related acute lung injury (TRALI); and decreased incidence of graft-versus-host disease (GVHD). Several countries have implemented universal leukoreduction protocols for transfused cellular blood products. The proposed benefits and cost-efficiency of universal leukoreduction have generated significant controversy within transfusion medicine and are not mandatory in the United States at this time.
      2. Hypotensive reactions associated with the use of bedside leukocyte reduction filters have been reported. The pathophysiology may involve activation of bradykinin by the leukocyte filter, and the hypotensive effect may be exaggerated in patients taking ACE inhibitors. When this reaction occurs, the transfusion should be stopped and the blood pressure supported. These interventions usually result in rapid resolution of hypotension. Products that are leukoreduced in the blood bank may carry a lower risk of this hypotensive reaction, as bradykinin is rapidly metabolized in stored blood.
  3. Massive transfusion is traditionally defined as transfusion of 10 or more units of PRBCs, or one BV, within a 24-hour period. When anticipating or initiating a large volume transfusion, coordination with the blood bank is crucial; therefore, many institutions have developed massive transfusion protocols to ensure availability and rapid mobilization of blood products when activated. The decision to activate a massive transfusion protocol may be complex but can be guided by validated clinical scoring systems such as the ABC score. Initial management should be aimed at correcting drivers of hemorrhage (eg, giving several units of FFP to correct a greatly elevated INR) prior to administering blood components according to any standard ratio. Some evidence suggests that transfusion of platelets, FFP, and PRBCs in a 1:1:1 ratio may be superior to a 1:1:2 ratio in promoting hemostasis and reducing mortality related to hemorrhage in the setting of trauma (see Chapter 35 for further discussion). Platelet counts may also be expected to fall by approximately 50% for each BV that is hemorrhaged; therefore, the early transfusion of platelets and consideration of antifibrinolytics may be beneficial.
  4. Blood substitutes. Despite years of research intent upon finding a blood substitute capable of oxygen transport, none provides significant clinical usefulness at this time. Hemoglobin-based oxygen carriers trialed to date have been shown to scavenge nitric oxide, provoke inflammation, and produce other harms that outweigh their potential benefits. These products continue to be an area of research.