Whole blood can provide improved oxygen-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.
Red blood cells (RBCs)
Packed RBCs are ordinarily the component of choice with which to increase hemoglobin (Hb). Indications depend on the patient. Oxygen-carrying capacity may be adequate with Hb levels as low as 7 g/dL (70 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 (10 g/L), and the hematocrit (Hct) by about 3%, above the pretransfusion 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, RBCs with rare phenotypes of antigens are used; these are usually frozen for storage.
Washed RBCs are free of almost all traces of plasma, most white blood cells, and platelets. They are generally given to patients who have severe reactions to plasma (eg, severe allergies, paroxysmal nocturnal hemoglobinuria, IgA immunization). In IgA-immunized patients, blood collected from IgA-deficient donors may be preferable for transfusion.
WBC-depleted RBCs (leukoreduced) are prepared with special filters that remove ≥ 99.99% of white blood cells. 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 human leukocyte antigen (HLA) alloimmunization to help prevent refractoriness to platelet transfusion (failure to achieve the target level of blood platelets after platelet transfusion).
Fresh frozen plasma
Fresh frozen plasma (FFP) is an unconcentrated source of all clotting factors without platelets. Indications include correction of bleeding secondary to clotting factor deficiencies for which specific factor replacements are unavailable or to multifactor deficiency states (eg, massive transfusion, disseminated intravascular coagulation [DIC], liver failure). FFP is used for urgent warfarin reversal only when prothrombin complex concentrate (PCC is the first choice) is unavailable. FFP is ineffective in managing bleeding due to direct factor Xa inhibitors. FFP can supplement RBCs when whole blood is unavailable for neonatal exchange transfusion. FFP should not be used simply for volume expansion or correction of mild to moderate coagulopathy before surgical procedures.
Pathogen-inactivated plasma obtained by treatment using the solvent detergent method is available to avoid transmission of almost all pathogens. During COVID-19 (SARS-CoV-2) pandemic, the convalescent plasma donated by a person who has fully recovered from this infection has been used as an option for treatment of COVID-19 with variable success. Convalescent plasma has been used in the past during Ebola and influenza H1N1 epidemics.
Cryoprecipitate
Cryoprecipitate is a concentrate prepared from fresh frozen plasma. Each concentrate usually contains about 80 units each of factor VIII and von Willebrand factor and about 250 mg of fibrinogen. It also contains ADAMTS13 (an enzyme that is deficient in congenital thrombotic thrombocytopenic purpura), and factor XIII. Although originally used for hemophilia and von Willebrand 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 syndrome (hemolysis, elevated liver enzymes, and low platelet count), and rare factor XIII deficiency when human coagulation factor XIII concentrate is unavailable. In general, it should not be used for other indications. A pathogen-inactivated pooled cryoprecipitate is now available that can be used as a source of fibrinogen. It has the advantage that it can be thawed and stored at room temperature for up to 5 days unlike standard cryoprecipitate that needs to be thawed from -18° C and has to be used within 4 hours.
White blood cells (WBCs)
Granulocytes may be transfused when sepsis occurs in a patient with profound persistent neutropenia (neutrophils < 500/mcL [0.5 × 109/L]) who is unresponsive to antibiotics. Granulocytes must be given within 24 hours 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 mcg) must be given to an Rh-negative mother immediately after abortion or delivery (live or stillborn) unless the infant is Rho(D) and Du negative or the mother’s serum already contains anti-Rho(D). If fetomaternal hemorrhage is > 30 mL, a larger dose is needed. If hemorrhage of this amount 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 test).
RhIg is also used to treat immune thrombocytopenia (ITP), in which case it is given IV.
Other immune globulins are available for postexposure prophylaxis for patients exposed to a number of infectious diseases, including cytomegalovirus, hepatitis A, hepatitis B, measles, rabies, respiratory syncytial virus, rubella, tetanus, smallpox, and chickenpox (for usage, see under specific disease).
Platelets
Platelet concentrates are used
To prevent bleeding in asymptomatic severe thrombocytopenia (platelet count < 10,000/mcL (<10 × 109/L))
For bleeding patients with less severe thrombocytopenia (platelet count < 50,000/mcL (< 50 × 109/L))
For bleeding patients with platelet dysfunction due to antiplatelet drugs but with normal platelet count
For patients receiving massive transfusion that causes dilutional thrombocytopenia
Platelet concentrates are also sometimes used before invasive surgery, particularly with extracorporeal circulation for > 2 hours (which often makes platelets dysfunctional). One platelet concentrate unit increases the platelet count by about 10,000/mcL, and adequate hemostasis is achieved with a platelet count of about 10,000/mcL (10 × 109/L) in a patient without complicating conditions, and about 50,000/mcL (50 × 109/L) for those undergoing surgery. Therefore, platelet concentrates derived from a pool of 4 to 5 units of whole blood 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 plateletpheresis, provides enough platelets from a single donation (equivalent to 4 to 5 whole blood 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 (called refractoriness), possibly because of splenic sequestration, platelet consumption due to disseminated intravascular coagulation, or destruction due to HLA or platelet-specific antigen alloimmunization (and immune-mediated destruction). If patients are refractory to transfusion, they are tested for alloimmunization if possible. Patients with immune-mediated destruction may respond to pooled whole blood platelets (because of greater likelihood that some units are HLA compatible), platelets from family members, or ABO- or HLA-matched platelets. HLA alloimmunization may be mitigated by transfusing WBC-depleted RBCs and WBC-depleted platelet concentrates.
Pathogen-inactivated platelets, inactivated by using a chemical (amotosalen), are also available for clinical use.
Other products
Irradiated blood products are used to prevent graft-vs-host disease in patients at risk.
Many attempts have been made to develop blood substitutes using inert chemicals (eg, perfluorocarbons) or hemoglobin solutions to carry and deliver oxygen to tissues. Although these hemoglobin substitutes had promising ability to deliver oxygen to tissues during an emergency, several clinical trials have failed due to increased mortality and severe adverse cardiovascular toxicities (eg, hypotension). Attempts to regenerate platelets and RBCs from various stem cell sources are underway.
Hematopoietic 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.