There are a variety of blood products, pharmacologic agents, and procedures that can be utilized to treat anemia, thrombocytopenia, and bleeding disorders. Here is a brief overview of the products and services available:
Packed red blood cells (PRBCs) are made from a unit of whole blood by centrifugation and removal of most of the plasma, leaving a unit with a hematocrit of about 60%. One PRBC unit will raise the hematocrit of a standard adult patient by 3% (or about 1%/mL/kg in a child - 12%/25 kg with the standard 300 mL PRBC unit). PRBCs are used to replace red cell mass when tissue oxygenation is impaired by acute or chronic anemia.
FFP contains all factors of the soluble coagulation system, including the labile factors V and VIII. FFP is indicated when a patient has MULTIPLE factor deficiencies and is BLEEDING. Note that FFP SHOULD NEVER be used as a plasma expander.
Cryoprecipitate (cryo) contains a concentrated subset of FFP components including fibrinogen, factor VIII coagulant, vonWillebrand factor, and factor XIII. Cryoprecipitate is used for hypofibrinogenemia, vonWillebrand disease, and in situations calling for a "fibrin glue." Cryo IS NOT just a concentrate of FFP. In fact, a unit of cryo contains only 40-50% of the coag factors found in a unit of FFP, but those factors are more concentrated in the cryo (less volume).
A single platelet unit is derived from one whole blood unit collected. Platelets are stored at room temperature and CANNOT be frozen. They must be used in 5 days. Pooled platelets from multiple donors from whole blood collections are cheaper to produce but the exposure to the recipient increases.
A "six pack" of platelets can be obtained by apheresis from a single donor at one time. Thus, apheresis platelets give just "one donor" exposure to the recipient, but the cost is high. The recipient's HLA type can be "matched" to a platelet donor with a similar HLA type to deal with problems of HLA alloimmunization (in patients with prior transfusions or pregnancies). The expected incremental increase in platelet count for adults is 30 - 60 K for each "six pack" of platelets
Normal saline is used when providing vascular access and fluid volume when transfusing other products and pharmacologic agents. Normal saline is more readily accessible than albumin or FFP, it is relatively inexpensive, and it does not have the risk of viral transmission.
Albumin is useful as a plasma expander. Albumin is not always readily accessible and it is expensive, but it does not have risk of viral transmission.
Apheresis involves removal of whole blood from either a patient undergoing treatment or a donor who is providing a blood component (typically platelets). Using an instrument designed as a centrifuge, the components of whole blood are separated. One of the separated portions is withdrawn and the remaining components are retransfused. The components which are separated off and withdrawn include: plasma (plasmapheresis), platelets (plateletpheresis), and leukocytes (leukapheresis).
Indications for Blood Product Usage
There are situations identified in which blood products may be needed:
Packed RBCs: generally indicated with a hemoglobin of 7 to 8 g/dL, a markedly decreased oxygen saturation and/or orthostatic hypotension. There is indication that the patient needs additional oxygen carrying capacity.
Platelets: generally indicated for a platelet count of less than 50,000/microliter and there is active bleeding, or if a procedure such as surgery is to be performed. Spontaneous bleeding is unlikely until the platelet count drops below 10,000 to 20,000/microliter.
FFP: generally indicated when a patient has multiple factor deficiencies and is bleeding, or for thrombotic thrombocytopenic purpura (TTP). The PT and PTT will be prolonged, and the INR generally should be greater than 1.6.
Cryo: generally indicated for hypofibrinogenemia, vonWillebrand disease, and in situations calling for a "fibrin glue."
There are specialized blood products for situations in which cells or substances in the unit need to be reduced or removed:
Washed Red Blood Cells
A unit of packed red blood cells (PRBCs) is washed to reduce plasma proteins. This reduces the risk for allergic transfusion reactions. Washing reduces immunoglobulins, such as anti-IgA that could cause anaphylactic transfusion reactions in persons with selective IgA deficiency.
Red blood cell and platelet units may be filtered to remove most of the leukocytes (white blood cells). This may reduce the risk for febrile transfusion reactions, may help prevent alloimmunizaton to MHC (HLA) donor antigens, and help reduce the risk for cytomegalovirus (CMV) infection.
Irradiation is needed to destroy all living leukocytes (white blood cells), particularly lymphocytes that could cause transfusion associated graft versus host disease (TAGVD).