Buy the Book PDA Download

Update Me E-mail alerts The Merck Manual Minute

Print This Topic Email This Topic

Whole blood can provide improved O₂-carrying capacity, volume expansion, and replacement of clotting factors and was previously recommended for rapid massive blood loss. However, because component therapy is equally effective and is a more efficient use of donated blood, whole blood is not generally available in the US.

RBCs: Packed RBCs are ordinarily the component of choice with which to increase Hb. Indications depend on the patient. O₂-carrying capacity may be adequate with Hb levels as low as 7 g/L in healthy patients, but transfusion may be indicated with higher Hb levels in patients with decreased cardiopulmonary reserve or ongoing bleeding. One unit of RBCs increases an average adult's Hb by about 1 g/dL and his Hct by about 3% of the pretransfusion Hct value. When only volume expansion is required, other fluids can be used concurrently or separately. In patients with multiple blood group antibodies or with antibodies to high-frequency RBC antigens, rare frozen RBCs are used.

Washed RBCs are free of almost all traces of plasma, most WBCs, and platelets. They are generally given to patients who have severe reactions to plasma (eg, severe allergies, paroxysmal nocturnal hemoglobinuria, or IgA immunization). In IgA-immunized patients, blood collected from IgA-deficient donors may be preferable for transfusion.

WBC-depleted RBCs are prepared with special filters that remove ≥ 99.99% of WBCs. They are indicated for patients who have experienced nonhemolytic febrile transfusion reactions, for exchange transfusions, for patients who require cytomegalovirus-negative blood that is unavailable, and possibly for the prevention of platelet alloimmunization.

Fresh frozen plasma: Fresh frozen plasma (FFP) is an unconcentrated source of all clotting factors without platelets. Indications include correction of bleeding secondary to factor deficiencies for which specific factor replacements are unavailable, multifactor deficiency states (eg, massive transfusion, disseminated intravascular coagulation [DIC], liver failure), and urgent warfarin Some Trade Names
COUMADIN
Click for Drug Monograph
reversal, although prothrombin complex concentrate (PCC) should be the first choice, if available. FFP can supplement RBCs when whole blood is unavailable for exchange transfusion. FFP should not be used simply for volume expansion.

Cryoprecipitate: Cryoprecipitate is a concentrate prepared from FFP. Each concentrate usually contains about 80 units each of factor VIII and von Willebrand factor and about 250 mg of fibrinogen. It also contains fibronectin and factor XIII. Although originally used for hemophilia and von Willebrand's disease, cryoprecipitate is currently used as a source of fibrinogen in acute DIC with bleeding, treatment of uremic bleeding, cardiothoracic surgery (fibrin glue), obstetric emergencies such as abruptio placentae and HELLP (hemolysis, elevated liver enzymes, and low platelet count) syndrome, and rare factor XIII deficiency. In general, it should not be used for other indications.

WBCs: Granulocytes may be transfused when sepsis occurs in a patient with profound persistent neutropenia (WBCs < 500/μL) who is unresponsive to antibiotics. Granulocytes must be given within 24 h of harvest; however, testing for HIV, hepatitis, human T-cell lymphotropic virus, and syphilis may not be completed before infusion. Because of improved antibiotic therapy and drugs that stimulate granulocyte production during chemotherapy, granulocytes are seldom used.

Immune globulins: Rh immune globulin (RhIg), given IM or IV, prevents development of maternal Rh antibodies that can result from fetomaternal hemorrhage. The standard dose of intramuscular RhIg (300 μg) must be given to an Rh-negative mother immediately after abortion or delivery (live or stillborn) unless the infant is Rh₀(D) and D^u negative or the mother's serum already contains anti-Rh₀(D). If fetomaternal hemorrhage is > 30 mL, a larger dose is needed. If this is suspected, testing of the volume of fetomaternal hemorrhage begins with the screening rosette test, which, if positive, is followed by a quantitative test (eg, Kleihauer-Betke). RhIg is given IV only when IM administration is contraindicated (eg, patients with coagulopathy).

Other immune globulins are available for postexposure prophylaxis for patients exposed to a number of infectious diseases, including cytomegalovirus, hepatitis A and B, measles, rabies, respiratory syncytial virus, rubella, tetanus, smallpox, and varicella (for usage, see under specific disease).

Platelets: Platelet concentrates are used to prevent bleeding in asymptomatic severe thrombocytopenia (platelet count < 10,000/μL), for bleeding patients with less severe thrombocytopenia (platelet count < 50,000/μL), for bleeding patients with platelet dysfunction due to antiplatelet drugs but with normal platelet count, for patients receiving massive transfusion that causes dilutional thrombocytopenia, and sometimes before invasive surgery, particularly with extracorporeal circulation for > 2 h (which often makes platelets dysfunctional). One platelet concentrate increases the platelet count by about 10,000/μL, and adequate hemostasis is achieved with a platelet count of about 10,000/μL in a patient without complicating conditions and about 50,000/μL for those undergoing surgery. Therefore, 4 to 6 random donor platelet concentrates are commonly used in adults.

Platelet concentrates are increasingly being prepared by automated devices that harvest the platelets (or other cells) and return unneeded components (eg, RBCs, plasma) to the donor. This procedure, called cytapheresis, provides enough platelets from a single donation (equivalent to 6 random platelet units) for transfusion to an adult, which, because it minimizes infectious and immunogenic risks, is preferred to multiple donor transfusions in certain conditions.

Certain patients may not respond to platelet transfusions, possibly because of splenic sequestration or platelet consumption due to HLA or platelet-specific antigen alloimmunization. These patients may respond to multiple random donor platelets (because of greater likelihood that some units are HLA compatible), platelets from family members, or ABO- or HLA-matched platelets. Alloimmunization may be mitigated by transfusing WBC-depleted RBCs and WBC-depleted platelet concentrates.

Other products: Irradiated blood products are used to prevent graft-vs-host disease in patients at risk (see Transfusion Medicine: Graft-vs-host disease (GVHD)). Blood substitutes are being developed that use inert chemicals or hemoglobin solutions to carry and deliver O₂ to tissues. Perfluorocarbons are chemically and biologically inactive and are capable of dissolving O₂ and CO₂ under pressure. Because perfluorocarbons are not water miscible, they are prepared as emulsions. They are undergoing phase II and III clinical trials. Hb-based O₂ carrier solutions are undergoing phase III clinical trials in the US. Hb, human or bovine, is chemically modified, producing a solution capable of O₂ transport. These solutions can be stored at room temperature for up to 2 yr, making them attractive for transport to the site of trauma or to the battlefield. However, both perfluorocarbons and Hb-based O₂ carriers are cleared from plasma within 24 h.

Hematopoietic progenitor cells (stem cells) from autologous or allogenic donors can be transfused as a way of reconstituting hematopoietic function (particularly immune function) in patients undergoing myeloablative or myelotoxic therapy (see Transplantation: Hematopoietic Stem Cell Transplantation).

Last full review/revision November 2006 by Ravindra Sarode, MD

Content last modified November 2006