Transfusion and Pheresis Therapy

TRANSFUSIONS 

Whole Blood Transfusion

Indicated when acute blood loss is sufficient to produce hypovolemia, whole blood provides both oxygen-carrying capacity and volume expansion.In acute blood loss, hematocrit may not accurately reflect degree of blood loss for 48 h until fluid shifts occur. 

Red Blood Cell Transfusion

Indicated for symptomatic anemia unresponsive to specific therapy or requiring urgent correction.Packed RBC transfusions may be indicated in pts who are symptomatic from cardiovascular or pulmonary disease when Hb is between 70 and 90 g/L (7 and 9 g/dL).Transfusion is usually necessary when Hb _ 70 g/L (_7 g/dL).One unit of packed RBCs raises the Hb by approximately 10 g/L (1 g/dL).If used instead of whole blood in the setting of acute hemorrhage, packed RBCs, fresh-frozen plasma (FFP), and platelets in an approximate ratio of 3:1:10 units are an adequate replacement for whole blood.Removal of leukocytes reduces risk of alloimmunization and transmission of CMV.Washing to remove donor plasma reduces risk of allergic reactions.Irradiation prevents graft-versus-host disease in immunocompromised recipients by killing alloreactive donor lymphocytes.Avoid related donors.

Other Indications (1) Hypertransfusion therapy to block production of defective cells, e.g., thalassemia, sickle cell anemia; (2) exchange transfusion— hemolytic disease of newborn, sickle cell crisis; (3) transplant recipients— decreases rejection of cadaveric kidney transplants.

Complications (See Table 5-1) (1) Transfusion reaction—immediate or delayed, seen in 1–4% of transfusions; IgA-deficient pts at particular risk for severe reaction; (2) infection—bacterial (rare); hepatitis C, 1 in 1,600,000 transfusions; HIV transmission, 1 in 1,960,000; (3) circulatory overload; (4) iron overload—each unit contains 200–250 mg iron; hemachromatosis may develop after 100 U of RBCs (less in children), in absence of blood loss; iron chelation therapy with deferoxamine indicated; (5) graft-versus-host disease; (6) alloimmunization. 

Autologous Transfusion

Use of pt’s own stored blood avoids hazards of donor blood; also useful in pts with multiple RBC antibodies.Pace of autologous donation may be accelerated using erythropoietin (50–150 U/kg SC three times a week) in the setting of normal iron stores. 

Platelet Transfusion

Prophylactic transfusions usually reserved for platelet count _ 10,000/_L (_20,000/_L in acute leukemia).One unit elevates the count by about 10,000/ _L if no platelet antibodies are present as a result of prior transfusions.Efficacy assessed by 1-h and 24-h posttransfusion platelet counts.HLA-matched singledonor platelets may be required in pts with platelet alloantibodies.

Transfusion of Plasma Components

FFP is a source of coagulation factors, fibrinogen, antithrombin, and proteins C and S.It is used to correct coagulation factor deficiencies, rapidly reverse warfarin effects, and treat thrombotic thrombocytopenic purpura (TTP).Cryoprecipitate is a source of fibrinogen, factor VIII, and von Willebrand factor; it may be used when recombinant factor VIII or factor VIII concentrates are not available. 

THERAPEUTIC HEMAPHERESIS

Hemapheresis is removal of a cellular or plasma constituent of blood; specific procedure referred to by the blood fraction removed.  

Leukapheresis

Removal of WBCs; most often used in acute leukemia, esp.acute myeloid leukemia (AML) in cases complicated by marked elevation (_100,000/_L) of the peripheral blast count, to lower risk of leukostasis (blast-mediated vasoocclusive events resulting in CNS or pulmonary infarction, hemorrhage).Leukapheresis is increasingly being used to harvest hematopoietic stem cells from the peripheral blood of cancer pts; such cells are then used to promote hematopoietic reconstitution after high-dose myeloablative therapy. 

Plateletpheresis

Used in some pts with thrombocytosis associated with myeloproliferative disorders with bleeding and/or thrombotic complications.Other treatments are generally used first.Also used to enhance platelet yield from blood donors. 

Plasmapheresis Indications

(1) Hyperviscosity states—e.g., Waldenstro¨m’s macroglobulinemia; (2) TTP; (3) immune-complex and autoantibody disorders—e.g., Goodpasture’s syndrome, rapidly progressive glomerulonephritis, myasthenia gravis; possibly Guillain-Barre´, SLE, idiopathic thrombocytopenic purpura; (4) cold agglutinin disease, cryoglobulinemia.