Transfusion Therapy and Blood and Marrow Stem Cell Transplantation
Transfusion Therapy and Blood and Marrow Stem Cell Transplantation
TRANSFUSION THERAPY
Principles of Transfusion Therapy
Due to the potentially life-threatening consequences of blood type ABO incompatibility and disease transmission through blood products, transfusion therapy is limited to occasions when it is absolutely necessary and stringent screening techniques are required before transfusion begins. Alternatives to transfusion therapy should also be considered, as appropriate, such as erythropoietin-stimulating agents, iron supplementation, blood loss prevention during surgery, and volume replacement with other solutions. Blood product procurement, storage, preparation, and testing are regulated by the Food and Drug Administration (FDA), the American Association of Blood Banks, and the Joint Commission.
Blood Compatibility
Antigens
The surface membrane of the red blood cell (RBC) is characterized by glycoproteins known as antigens.
More than 400 different antigens have been identified on the RBC membrane.
There are fewer than a dozen clinically significant antigens, and of these, only two antigenic systems (ABO and Rh) require routine prospective matching before the transfusion.
The ABO blood group system is clinically the most significant because A and B antigens elicit the strongest immune response.
The presence or absence of A and B antigens on the RBC membrane determines the person’s ABO group (see
Table 27-1). The ability to make A or B antigens is inherited.
Antibody formation without specific exposure to the antigen is unique to the ABO system. Antibody directed against the missing antigens is produced in neonates by 3 months of age.
Antibodies
Antibodies (or immunoglobulins) are proteins produced by B lymphocytes; they consist of two light and two heavy chains that form a Y shape.
Antibodies generally have a high degree of specificity and interact only with the antigen that stimulated their production.
The five classes of immunoglobulins are determined by differences in their heavy chains: immunoglobulin (Ig) G, IgA, IgM, IgD, IgE.
The interaction of antibodies and antigens triggers the humoral immune response.
Antibodies against the A and B antigens are large IgM molecules. When they interact with and coat the A and B antigens on the RBC surface, the antibody/RBC complexes clump together (agglutinate).
Antibody/RBC complexes also activate the complement cascade, resulting in the release of numerous active substances and RBC lysis. The large antibody/RBC complexes also become trapped in capillaries, where they may cause thrombotic complications to vital organs, and in the reticuloendothelial system, where they are removed from circulation by the spleen.
The extent of the humoral response elicited by anti-A and anti-B interaction with A and B antigens depends on the quantity of antibody and antigen.
Other Red Blood Cell Antigens
Non-ABO RBC antigen-antibody reactions usually do not produce powerful immediate hemolytic reactions, but several have clinical significance.
After A and B, D is the most immunogenic antigen. It is part of the Rhesus system, which includes C, D, and E antigens.
D (Rh)-negative people do not develop anti-D without specific exposure, but have a high incidence of antibody development (alloimmunization) after exposure to D.
Two common methods of sensitization to these RBC antigens are by transfusion or fetomaternal hemorrhage during pregnancy and delivery.
Anti-D can complicate future transfusions and pregnancies. For the D (Rh)-negative person, exposure to D should be avoided by the use of Rh-negative blood products. In the case of Rh-negative mother and Rh-positive fetus, prophylaxis for exposure to D uses Rh immunoglobulin (RhoGAM), which will prevent anti-D formation.
Exposure to RBC antigens from other antigenic systems (such as Lewis, Kidd, or Duffy) may also cause alloimmunization, which becomes clinically significant in people who receive multiple blood products for extended periods of time.
Blood Transfusion Options
Autologous Transfusion
Before elective procedures, the patient may donate blood to be set aside for later transfusion. Patients may donate up to 3 days prior to surgery provided hemoglobin is greater than 11 g/dL.
Autologous RBCs can also be salvaged during some surgical procedures or after trauma-induced hemorrhage by use of automated cell-saver devices or by manual suction equipment.
Autologous blood products must be clearly labeled and identified.
Autologous transfusion eliminates the risks of alloimmunization, immune-mediated transfusion reactions, and transmission of disease, making it the safest transfusion choice.
Homologous Transfusion
With this most common option, volunteer donors’ blood products are assigned to patients randomly.
Before donation, volunteer donors receive information about the process, potential adverse effects, tests that will be performed on donated blood, postdonation instructions, and education regarding risk of human immunodeficiency virus (HIV) infection and signs and symptoms.
Donors are screened against eligibility criteria designed to protect donor and recipient (see
Table 27-2).
Directed Transfusion
In directed transfusion, blood products are donated by a person for transfusion to a specified recipient.
This option may be used in certain circumstances (eg, a parent who provides sole transfusion support for a child), but in general, no evidence exists that directed donation reduces transfusion risks.
Blood Product Screening
Serologic Testing
Routine laboratory testing is performed to assess the compatibility of a particular blood product with the recipient before release of the blood product from the blood bank (see
Table 27-3).
ABO group and Rh type: determines the presence of A, B, and D antigens on the surface of the patient’s RBCs.
Direct Coombs’ test: determines the antibody attached to the patient’s RBCs.
Crossmatch (compatibility test): detects agglutination of donor RBCs caused by antibodies in the patient’s serum.
Indirect Coombs’ test: identifies lower molecular-weight antibodies (IgG) directed against blood group antigens.
Screening for Infectious Diseases
Routine laboratory testing is performed to identify antigens or antibodies in donor blood that may indicate prior exposure to specific blood-borne diseases.
Such testing supplements other principles of donation designed to decrease the risk of disease transmission via blood products, including the use of volunteer donors, the exclusion of high-risk populations, and the screening of donors via health and social history.
Through the use of donor screening and blood testing, the risk of infections transmitted with donated blood is less than 1% and continues to decline.
Specific conditions screened for include:
Hepatitis: Per FDA recommendations, each unit of blood is tested for the presence of hepatitis B core antibody, surface antigen, and more recently hepatitis B viral DNA through nucleic acid testing (NAT). Hepatitis C antibody and viral DNA tests (NAT) are also completed.
HIV-1 and HIV-2: tests for prior exposure to the virus.
All blood products in the United States have been screened since the test first became available in 1985. Current tests include testing for antibodies with enzyme-linked immunosorbent assay or enzyme immunoassay or antigen with the P24 test. NAT is becoming more widely used and provides a mechanism to look for the presence of HIV-1 and HIV-2 before antibody formation.
Because antibody to the virus is not produced until at least 6 weeks after exposure, diligent donor screening
and exclusion of high-risk groups (eg, homosexual men, intravenous [IV] drug abusers, prostitutes, and sexual partners of high-risk people) remain important parts of preventing transmission of HIV via blood products.
A low risk of HIV transmission (estimated to be less than 1/2,000,000 units of blood) remains.
Cytomegalovirus (CMV): tests for the antibody against CMV.
Approximately 50% to 75% of blood donors have been exposed to CMV and 10% to 20% carry CMV virus in their white blood cells (WBCs).
Patients with impaired immune function (eg, bone marrow and organ transplant recipients, premature babies) are at risk for CMV infection from transfused blood. It is recommended that these patients receive CMV sero-negative blood or leukoreduced products.
Syphilis: tests for the presence of antibody against the spirochete.
Bacteria: contamination of blood products with bacteria may occur during and after collection of blood. This risk is managed by adherence to sterile technique during phlebotomy and blood-processing procedures, correct storage techniques, visual inspection of blood products, and limitations on shelf life.
Other infections that may be transmitted via blood transfusions include West Nile virus, human T-cell lymphoma virus (HTLV) 1 and 2, human herpes virus-8 (implicated as the causative agent of Kaposi’s sarcoma), malaria, babesiosis, Chagas’ disease, and yersinia. Variant Creutzfeldt-Jacob disease has also been transmitted via blood transfusions, which has led to restrictions on donation by individuals who have lived in areas with bovine spongiform encephalopathy or “mad cow” disease.
Administration of Whole Blood and Blood Components
Whole blood and blood components are administered to increase the amount of oxygen being delivered to the tissues and organs, to prevent or stop bleeding because of platelet defects or because of deficiencies or coagulation abnormalities, and to combat infection caused by decreased or defective WBCs or antibodies (see
Procedure Guidelines 27-1, and
Standards of Care Guidelines 27-1, page 1007).
Whole Blood
Description
Consists of RBCs, plasma, plasma proteins, and approximately 60 mL anticoagulant/preservative solution in a total volume of approximately 500 mL.
Indications include acute, massive blood loss of greater than 1,000 mL, requiring the oxygen-carrying properties of RBCs and the volume expansion provided by plasma. In general, even acute loss of as much as one third of a patient’s total blood volume (1,000 to 1,200 mL) can be safely and rapidly replaced with crystalline or colloidal solutions.
Nursing and Patient Care Considerations
For rapid infusions of large volumes of whole blood, additional steps may be taken to deliver product rapidly and safely.
A small-pore (20 to 40 mm) filter may be used to remove microaggregates (platelets, WBCs) that have been identified in the lungs of massively transfused patients.
An approved blood warmer may be indicated to prevent hypothermia and cardiac arrhythmias associated with the rapid infusion of refrigerated solutions.
Electromechanical infusion devices to deliver blood at high flow rates can hemolyze RBCs and should be used with caution.
Observe closely for the most common acute complication associated with whole blood transfusion—circulatory overload (rise in venous pressure, distended neck veins, dyspnea, cough, crackles at bases of lungs).
Packed RBCs
Description
Consist primarily of RBCs, a small amount of plasma, and approximately 100 mL anticoagulant/preservative solution in a total volume of approximately 250 to 300 mL/unit.
Packed RBCs may be contaminated with WBCs that may increase the risk of minor transfusion reactions and alloimmunization. For patients who receive multiple blood products during a specific period (eg, patients with leukemia or aplastic anemia), packed RBCs may be further manipulated to remove WBCs (leukoreduced) by washing or freezing the product in the blood bank or by the use of small-pore (20 to 40 mm) leukoreduction filters during administration.
Indications include restoration or maintenance of adequate organ oxygenation with minimal expansion of blood volume.
Dosage: average adult dose administered is 2 units; pediatric doses are generally calculated as 5 to 15 mL/kg.
Nursing and Patient Care Considerations
Infuse at the prescribed rate. Generally, a unit can be given to an adult in 90 to 120 minutes. Pediatric patients are usually transfused at a rate of 2 to 5 mL/kg per hour.
To reduce the risk of bacterial contamination and sepsis, RBCs must be transfused within 4 hours of leaving the blood bank.
Observe closely (particularly during first 15 to 30 minutes) for the most common acute complications associated with packed RBCs, allergic and febrile transfusion reactions. Signs and symptoms of the more serious, but rare, hemolytic transfusion reactions are usually manifested during infusion of the first 50 mL.
NURSING ALERT
Evidence Base
DRUG ALERT Crystalloid solutions other than 0.9% saline and all medications are incompatible with blood products. They may cause agglutination or hemolysis.
