Ronan Desmond and Harvey G. Klein
BLOOD CELL ANTIGENS
Red blood cell (RBC) antigens are classified according to their biochemical, phenotypic, and immunologic characteristics. Based on these characteristics, they have been separated into blood group systems. Currently 30 major blood group systems are recognized, the most clinically relevant being ABO, Rh, Kell, Kidd, and Duffy. Clinically important alloantibodies (specific for antigens not found on the individuals red cells) can cause destruction of transfused red cells or are implicated in hemolytic disease of the newborn (HDN).
The antiglobulin or Coombs test (see below) is used to detect antibodies to red cell antigens and in crossmatching compatible blood units for transfusion. When a clinically important alloantibody is present in a recipient’s serum, antigen-negative blood must be selected. If the alloantibody is against a very high frequency antigen (present in greater than 90% of individuals) or when multiple alloantibodies are present, procurement of compatible blood may be difficult or impossible. Occasionally, the presence of red cell autoantibodies in the recipient makes all units appear incompatible. Further investigations are necessary in these cases to rule out an underlying alloantibody.
“Naturally occurring” antibodies such as anti-A and/or anti-B are present in the absence of prior sensitizing stimulus, whereas development of most other alloantibodies requires prior sensitization by exposure to the corresponding red cell antigen in a previous transfusion or pregnancy.
Blood group A individuals have naturally occurring anti-B
Blood group B individuals have naturally occurring anti-A
Blood group O individuals have naturally occurring anti-A and anti-B
Blood group AB individuals have neither anti-A nor anti-B
LABORATORY DETERMINATION OF MAJOR BLOOD GROUPS
An individual’s blood group is determined by performing a forward and reverse grouping (ABO typing):
In forward grouping, reagents of known antibody specificity (anti-A or anti-B) are added to the patient’s RBCs of unknown phenotype (A, B, AB, or O) and the mixtures are examined for visible agglutination; the absence of agglutination on combining the patient’s cells with anti-A or anti-B reagent indicates that the patient’s cells do not have the corresponding antigen. For example, red cells of group O will not agglutinate in the presence of anti-A and/or anti-B.
In reverse grouping, the patient’s serum is added to reagent cells of known phenotype (A, B, or O) and the mixtures are examined for visible agglutination; the presence of agglutination on combining the patient’s serum with reagent cells of A or B phenotype, indicates that the patient’s serum contains the corresponding antibody. For example serum containing anti-A and anti-B (blood group O) will agglutinate in the presence of both group A and group B red cells.
The forward and reverse groups must be consistent. A specific blood group may not be assigned with certainty until an ABO discrepancy is resolved.
Some common causes of apparent ABO discrepancies are1 presence of A or B subgroups,2 missing/ weakly reacting antibodies (can occur with newborns, the elderly, or in hypogammaglobulinemic states) or weak expression/absence of expected antigens (can occur with lymphoproliferative disorders and post hematopoietic stem cell transplantation, HSCT),3 presence of unexpected or nonspecific antibodies such as cold reactive alloantibodies or autoantibodies,4 interfering substances such as Wharton jelly from the umbilical cord of a newborn, or5 hyperproteinemic states causing Rouleaux formation.
ANTIGLOBULIN TEST
The antiglobulin test uses antibodies with specificity for immunoglobulins or complement to detect the presence of antibody (or complement) on the RBC surface or in a patient’s serum.
The direct antiglobulin test (DAT), or the direct Coombs test, detects the presence of antibody or complement coating RBC and may be positive in a variety of settings, including those listed below:
Hemolytic transfusion reactions
HDN (usually strongly positive)
Autoimmune hemolytic anemias (AIHA)
With some pharmacologic agents (penicillins, cephalosporins)
After administration of intravenous immunoglobulin (IVIG) or plasma (passively acquired)
Post marrow or organ transplant (passenger lymphocyte syndrome)
Autoimmune diseases
Some normal individuals
A positive DAT does not necessarily indicate in vivo hemolysis or shortened RBC survival. Falsepositive results may occur when Rouleaux formation is mistaken for agglutination.
The indirect antiglobulin test (IAT), or indirect Coombs test, is used to screen for antibodies when looking for compatible blood for transfusion (“type and screen”) and in the serologic cross-match (patient serum and donor/ reagent red cells). The IAT detects antibody present in the serum, but not bound to the RBC. When the IAT is positive, the antibody must be identified and the corresponding antigen always avoided in transfusions. A negative IAT does not necessarily indicate absence of alloantibodies: the titer of antibody may be below the level of detection or the antibody might be directed against a low incidence antigen (present in less than 1% of individuals) not present on reagent testing cells. A negative IAT does not guarantee that blood is compatible, nor does a weak IAT indicate that hemolysis is likely to be mild. A positive IAT always requires further investigation.
In AIHA, in which the antibody may be present in the serum and on the RBC of the patient, both the DAT and IAT may be positive.
BLOOD COMPATIBILITY
In general, blood components that contain more than 2 mL of RBC must be compatible with the patient’s plasma. Particular attention is paid to Rh type because less than 1 mL of RBC, a volume found in most platelet concentrates, is sufficient to sensitize an Rh-negative patient.1 Plasma-containing components, including platelet preparations, should be ABO compatible with the patient’s RBC when possible to prevent passive immune hemolysis from antibodies in the plasma (Table 24.1).
The most basic practical application of blood group serology involves the selection of compatible blood. The absence or presence of blood cell antigens can have important biological and clinical implications. Compatible blood takes time to prepare.
In an emergency, group O Rh-negative RBC may be released uncrossmatched with the consent of the requesting physician; testing will be completed after release. Group-specific red cells and an abbreviated crossmatch can be prepared in 15 minutes.
Fully tested red cells can be prepared in 45 to 60 minutes; cryopreserved RBC and fresh-frozen plasma (FFP) may take longer.
In the setting of transfusion or pregnancy in the previous 3 months a pretransfusion sample cannot be more than 3 days old.6
ABO INCOMPATIBILITY IN TRANSPLANT SETTINGS
Optimal results in HSCT rely on human leukocyte antigen (HLA) compatibility, so that selection of the recipient-donor pair is determined by similarity of HLA potentially at the expense of ABO compatibility. Because HLA and ABO genes are inherited independently, some (20%–40%) of these transplants will be ABO incompatible.1
Whereas ABO incompatibility does not appear to impact graft failure, potential complications of mismatches include acute or delayed hemolysis and delayed RBC engraftment.2-5
Minor Incompatibility
Donor’s serum contains antibodies against RBC antigens of the recipient (e.g., recipient blood group A, B, or AB, and donor blood group O)
Prior to infusion of the stem cell preparation, plasma containing anti-A and anti-B can be removed to prevent immediate postinfusion hemolysis of the recipient’s RBC (plasma reduction)
Of minor ABO-incompatible transplant recipients, 10% to 15% may experience abrupt onset of hemolysis 5 to 15 days posttransplant when immune-competent B lymphocytes in the graft mount a response against the recipient RBC antigens (passenger lymphocyte syndrome)
Hemolysis may be severe or even fatal unless recognized promptly
Major Incompatibility
Recipient’s serum contains antibodies against the RBC antigens of the donor (e.g., recipient group O and donor group A, B, or AB; recipient group A or B and donor group AB).
Hemolysis of RBC in the stem cell preparation upon infusion may occur if the graft is not processed to remove RBC prior to infusion (red cell reduction).
Post transplant, the recipient may produce antibodies against donor red cell antigens for months, especially with nonmyeloablative regimens.
RBC engraftment and erythropoiesis may be delayed, resulting in red cell aplasia.5,6
Minor and major (bidirectional) incompatibility between the donor and recipient occurs when each has antibodies against the ABO blood group antigens of the other (combination of group A donor and B recipient, or vice versa).
Table 24.2 describes appropriate transfusion management during transplantation. All transfusion components must be irradiated.
Rh Incompatibility
Rh incompatibility occurs in 10% to 15% of stem cell transplants. Transfusion practice is analogous to that of major and minor ABO incompatibility, but the consequences are less severe.
For Rh-negative recipients of Rh-positive hematopoietic stem cell preparations
Transplant product should be red cell reduced to decrease risk of alloimmunization similar to major ABO incompatibility
For Rh-positive recipient from Rh-negative donor previously alloimmunized to the Rh antigen
Monitor the patient for signs of delayed hemolysis (as in minor incompatibility).
BLOOD COMPONENTS AND DERIVATIVES
Blood Components and Transfusion Therapy
Blood components can be separated from whole blood by centrifugation or by apheresis. Approximately 29 million blood components (RBCs, platelets, plasma, cryoprecipitate) are transfused annually in the United States.
Storage and infusion of blood products
Blood components should be infused through standard 170 to 260 μm infusion filters to remove any clots that form during storage. 6
An approved infusion pump may be used for strict control of transfusion rate. Nonapproved pumps may damage or hemolyze cells.
Bedside leukoreduction filters may be used when leukoreduction is indicated for whole blood, packed RBCs, and platelets that have not been leukocyte reduced prior to storage.
Hypotensive reactions have been associated with bedside leukoreduction, especially in patients receiving angiotensin converting enzyme (ACE) inhibitors.
Allow blood to filter by gravity.
Granulocyte concentrates must never be infused through leukoreduction filters.
Whole blood and other cellular blood components may be infused with isotonic solutions: USP 0.9% NaCl (normal saline) and certain Food and Drug Administration (FDA) approved electrolyte solutions.
Cellular blood products must never be infused with hypertonic or hypotonic solutions, for example, solutions containing glucose or calcium, such as D5W (5% dextrose in water) or lactated Ringer solution as hemolysis, clotting, or agglutination of RBC may result.
Medications should never be added to blood components.
Never store blood components in unmonitored refrigerators in nursing units or surgical suites; the risk for administration of blood components to the wrong patient increases in these cases.
Return blood to storage (or blood bank) if transfusion is not started within 30 minutes of issue.
Warming devices with internal monitors are available for blood products to avoid transfusion of large volumes of cold fluid.
Blood components should never be warmed in uncertified devices (like microwave ovens or water baths) as hemolysis can result and can be lethal.
Most adverse transfusion reactions occur in the first 15 minutes:
Administration of blood products should start slowly and under close observation.
The time of transfusion should not exceed 4 hours as the risk of bacterial growth increases with time at room temperature.
If transfusion is anticipated to take longer, the transfusion service can divide the unit into smaller aliquots.
See Table 24.3 for blood component administration.
See Table 24.4 for indications for additional modifications to blood components.
Storage conditions for different blood components vary and are designed to maximize preservation and effectiveness:
Red cells are refrigerated (at 1–6°C) for up to 42 days.
Platelets are stored at room temperature and expire in 5 days.
Plasma components are stored frozen for a year (at −18°C) or more (at −65°C), but must be thawed before use and therefore are not immediately available.
As with any medical treatment, blood transfusion requires informed consent:
Patients must be advised of the indications and common adverse events as well as any potential alternatives to allogeneic transfusion.
Whole Blood
A unit of whole blood typically has a volume of 450 to 500 mL and a hematocrit of 35% to 45%. Whole blood is rarely available and infrequently used.
Indications: Acute hypovolemia with red cell loss, massive transfusion, and exchange transfusion Not indicated: Chronic anemia (in which blood volume is often increased)
Whole blood is not a source of functional platelets or granulocytes, which deteriorate in less than 24 hours at refrigerator temperatures.
Red Blood Cells
RBC (packed red cells) are separated from whole blood by centrifugation. A unit of RBC contains approximately 200 mL and a hematocrit of 60% to 80%. In general, 1 unit of packed RBC will increase the hemoglobin (Hb) by 1 g/dL in an average-sized adult. In the average pediatric patient, transfusion of 8 to 10 mL/kg of RBC is expected to increase hemoglobin by 3 g/dL. The decision to transfuse should be based on assessment of symptoms, coexisting or underlying medical conditions, and the cause of the anemia and patients should not be transfused based solely on their Hb level. The single adequately powered prospective study (ICU patients) and numerous observational studies indicated that patients with cardiovascular disease are more sensitive to anemia and do better at a higher Hb level.7,8
Indications: Treatment of symptomatic anemia.
While it is generally accepted that patients with Hb <6 g/dL should be transfused and that transfusion is rarely required when it exceeds 10 g/dL, the interval between these values is an area of controversy. Practice guidelines support an Hb level of less than 7 g/dL as generally acceptable for the initiation of RBC transfusion in asymptomatic patients.8,9 Patients at particular risk for bleeding (thrombocytopenia, recent hemorrhage) should be maintained at a higher Hb.
Not indicated: RBC should not be transfused for volume expansion or nutritional purposes Transfusion is rarely indicated in otherwise treatable anemia, including anemia associated with Vitamin B12, iron, or folate deficiency; if symptoms are severe, these patients may benefit from a single-unit transfusion as the underlying cause is corrected.
Platelets
Platelets may be separated from whole blood shortly after collection (“random donor” or “whole blood-derived” platelet concentrates) or collected by apheresis (“single donor” or “apheresis platelets”). A therapeutic dose of platelets for an adult is 1 unit of platelets (5.5 × 1010 platelets) per 10 kg of body weight, which should increase the platelet count in an average-sized adult by approximately 5,000/μL. Each apheresis (single-donor) platelet product is expected to contain approximately 3 × 1011 platelets, roughly equivalent to 4 to 6 units of random donor platelets. Indications for use are the same for both preparations. Alloimmunized refractory patients may require single-donor HLA-matched platelets. Single-donor platelets also offer the additional advantage of decreased donor exposure and a lower risk of bacterial sepsis.
Indications: Prevention and treatment of hemorrhage in patients with thrombocytopenia or platelet function defects.
Not indicated: Bleeding unassociated with thrombocytopenia (in the absence of a clinically significant platelet function defect), other defects in hemostasis (such as factor deficiencies).
Platelets are usually contraindicated in thrombotic thrombocytopenic purpura (TTP),10 because they could potentially precipitate thrombosis, but this has been recently challenged.11 However, patients with TTP who develop life-threatening hemorrhage may benefit from a cautious trial of platelets.
The threshold for prophylactic platelet transfusion varies based on the patient’s underlying condition and likelihood of hemorrhage:
A threshold of 10,000/μL is effective in preventing morbidity and mortality from bleeding in stable oncology patients undergoing chemotherapy.
A platelet count greater than 50,000/μL is desirable prior to invasive procedures and in the immediate postprocedure period.
Platelet counts closer to 100,000/μL may be prudent for patients at high risk for intracranial hemorrhage, such as those with cerebral leukostasis, or when undergoing neurosurgical or ocular procedures.
Stable chronically thrombocytopenic patients, such as those with aplastic anemia or myelodysplasia, may tolerate platelet counts as low as 5,000/μL in the absence of complicating factors including fever, infection, and additional defects in hemostasis. 1
More aggressive support is indicated for patients who are unstable—febrile, infected, receiving multiple medications—especially if the platelet counts are decreasing.1,12
Platelet transfusions should be monitored by a 1 to 24 hour posttransfusion platelet or complete blood count (CBC) to assess response and guide subsequent transfusion therapy. A corrected count increment (CCI) may be used to determine the increase in platelet count in an individual post platelet transfusion:
*Posttransfusion platelet count, expressed per microliter, is best obtained 15 minutes to 1 hour posttransfusion
**Body surface area = the square root of [(height in cm × weight in kg)/3,600], expressed in meters squared
***Expressed as multiples of 1 × 1011
An absolute posttransfusion increment of 10,000/μL or greater (approximately 2,000/μL per unit of random donor platelets) in an average-sized adult corresponds to a CCI of 5,000.
Platelet Refractoriness
Patients who respond poorly to repeated platelet infusions are termed refractory. Posttransfusion platelet counts (performed at 1 and 24 hours) are useful tests to determine refractoriness. The CCI should also be calculated and failure to achieve a CCI of 5,000 or greater is cause to suspect platelet refractoriness. Refractoriness may be immune or nonimmune mediated. Immune-mediated refractoriness indicates alloimmunization to HLA or human platelet antigens (HPA).
Nonimmune-mediated causes of platelet refractoriness: fever, infection, splenomegaly, disseminated intravascular coagulation (DIC), massive bleeding, and medications that enhance platelet destruction; more likely to affect the 24-hour posttransfusion count.
Immune-mediated platelet refractoriness caused by alloimmunization to HLA and human platelet antigens usually associated with multiparity or exposure to nonleukocyte reduced platelet transfusions; more likely to affect the 1 hour posttransfusion count.
In practice, the distinction between immune- and nonimmune-mediated platelet refractoriness becomes less clear as alloimmunized patients often have multiple medical issues predisposing to nonimmune refractoriness. When immune-mediated platelet refractoriness is suspected and CCI is less than 5,000 after each of two platelet transfusions the following steps should be taken:
ABO-compatible fresh (less than 72 hours in storage) platelets should be used for two subsequent transfusions
If CCI still does not exceed 5,000, HLA antibody screen to detect alloantibodies, or commercial platelet compatibility tests should be performed
When alloantibodies with broad specificity are found (for HLA A and B loci) platelets from HLA-matched donors are indicated
Crossmatch compatible platelets may be beneficial when HLA antibody status of the recipient cannot be determined, HLA-matched platelets cannot be obtained, or when the patient is refractory to HLA-matched platelets (up to 40% to 50% of cases)
Corticosteroids, washed platelets, or IVIG have not proved useful in the treatment of refractoriness
Granulocytes
Granulocytes are collected by apheresis for specific patients, from donors who are mobilized prior to collection with corticosteroids and/or granulocyte colony-stimulating factor [G-CSF].
Granulocytes can be stored at room temperature for only up to 24 hours post collection but optimally should be administered within 6 hours of collection.
Granulocyte collections have a volume of 250 mL and contain plasma, approximately 30 mL RBC, and variable amounts of mononuclear leukocytes and platelets.
Granulocyte concentrates should be ABO, Rh, and RBC crossmatch compatible.
Products should be irradiated because of the presence of viable lymphocytes in the collection.
The minimal therapeutic dose is 1 × 1010 granulocytes/unit however, increments are unlikely to be seen unless greater than 3 to 4 × 1010 granulocytes/unit are infused. 1
Indications: Patients with absolute neutrophil counts of less than 0.5 × 109/L and documented bacterial or fungal infection refractory to antimicrobials. Recipients must have a reasonable expectation of achieving hematopoietic recovery or engraftment (endogenous granulocyte production). Infants with bacterial sepsis, whose granulocyte counts are less than 3 × 109/L with postmitotic neutrophils comprising less than 10% of their nucleated marrow cells, may benefit from granulocyte transfusions.1
A 1 to 6 hour posttransfusion CBC with differential for determination of ANC may help assess efficacy. A 6-hour posttransfusion increment may be higher than a 1-hour posttransfusion ANC because granulocytes travel to the lungs before equilibrating in peripheral blood. If the patient’s ANC fails to reach expected levels or if a reaction occurs, an HLA antibody screen and tests for antibodies to human neutrophil antigens (HNA) are indicated to look for an immunologic cause.
Not indicated: Patients whose bone marrow function is not likely to recover. Contraindicated in patients with prior severe pulmonary reactions to HLA or HNA antibodies or HLA or HNA alloimmunization.
Alloimmunized patients may develop chills, fever, rigors, shortness of breath, wheezing, pulmonary infiltrates, cyanosis, and hypotension6,13; rigors and fever may respond to intravenous meperidine.
Pulmonary toxicity may be exacerbated when granulocytes and amphotericin B are administered in close temporal proximity.14 At NIH, amphotericin B administration and granulocyte transfusions are separated by at least 4 hours.
Granulocyte transfusion therapy should be evaluated after an initial course of four infusions and then periodically.
Granulocyte concentrates may contain leukocyte-associated pathogens such as cytomegalovirus (CMV), which may be a particular concern for immunosuppressed stem cell transplant recipients, solid organ transplant recipients, neonates undergoing extracorporeal membrane oxygenation, and low birth weight and premature infants.
While granulocyte transfusions decrease the length of bacterial infection, proof that granulocyte transfusions decrease mortality in any situation has been elusive. 15,16
Fresh-Frozen Plasma
Plasma separated from whole blood or collected by apheresis and frozen within 8 hours is labeled FFP. FFP contains plasma proteins at the time of thaw in about the same concentrations as at the time of collection. The volume of a unit of plasma is approximately 200 mL.
By convention, 1 mL of FFP is expected to provide 1 unit of activity of all factors (except labile factors V and VIII). In practice, individual units may vary in content.
The dose used is 10 to 20 mL/kg in adults (equivalent to approximately 4 to 6 units of FFP) to increase coagulation factor levels by 20%.
Indications: Correction of multiple clotting factor deficiencies in patients who are bleeding or prior to an invasive procedure, replacement of factors in consumptive coagulopathy, coagulation factor deficiencies caused by liver disease, dilutional coagulopathy after massive transfusion, replacement fluid for plasma exchange in the treatment of TTP, rapid reversal of warfarin (Coumadin) effect, replacement of single congenital factor deficiencies when no virus-safe fractionated product is available (mostly applies to factor V deficiency).
A PT greater than 1.5 normal or APTT ratio greater than 2.0 in the presence of microvascular bleeding is a guide to consider treatment. 9
Note, in the setting of life-threatening bleeding associated with Coumadin therapy where rapid reversal is necessary or in overanticoagulated patients with volume overload a more appropriate therapy is Prothrombin Complex Concentrate (PCC). See section Blood Derivatives.
Not indicated: Volume expansion, protein replacement in nutritional deficiencies.
Cryoprecipitate
Cryoprecipitate (cryo) is the cold-insoluble portion of plasma which contains factor VIII, fibrinogen, von Willebrand factor, factor XIII, and fibronectin. Ordinarily stored frozen, cryo can be kept at room temperature for up to 6 hours; on pooling it must be transfused within 4 hours.
Compatibility testing is unnecessary.
A unit of cryo is usually less than 15 mL of plasma and contains more than 80 international units (IU) of factor VIII and more than 150 mg of fibrinogen.
One unit of cryo can increase fibrinogen in an average adult by 5 to 10 mg/dL.
A therapeutic dose for an adult is 80 to 150 mL of cryo (8 to 10 units pooled).
Indications: Treatment of congenital fibrinogen deficiency, dysfibrinogenemia, factor XIII deficiency, DIC (if fibrinogen <1.0 g/L).
Note a pathogen-inactivated fibrinogen concentrate has recently become available in the United States for treatment of congenital fibrinogen deficiency.
Cryo has also been used to correct the platelet defect of uremic bleeding, although with variable success.
The dosage of cryo depends on the underlying deficiency and on the plasma volume of the patient. To determine the number of bags of cryo to replace fibrinogen
*The plasma volume for an average adult = (1 {{{727}}} percent hematocrit/100) × patient weight in kg × 70 mL/kg. For infants and children under 40 kg, the plasma volume = (1{{{727}}}percent hematocrit/100) × patient weight in kg × 80 to 85 mL/kg.
Not indicated: Factor VIII deficiency and von Willebrand disease for which more specific and safer products now exist.
Hematopoietic Stem and Progenitor Cells
Optimal outcomes in HSCT depend on the successful procurement of cells from patients (autografts) or donors (allografts). Several recent developments in this field have improved clinical outcomes making this approach a safe and effective therapy for a variety of malignant and nonmalignant disorders.
Stem cell sources now include related and unrelated bone marrow, peripheral blood and umbilical cord blood. The vast majority of HSCT now uses mobilized peripheral blood although guidelines for management of aplastic anemia still recommend using a bone marrow source if possible.17
Historically, mobilization of stem cells into peripheral blood for autografting was done using myelosuppresive chemotherapy such as cyclophosphamide as increased numbers of cells entered the circulation during the recovery phase of the bone marrow. In the late 1980s G-CSF and GM-CSF became available and were used either alone or in combination with chemotherapy as mobilizing agents. G-CSF is now the standard for this indication.
A significant proportion of patients do not mobilize with G-CSF with or without chemotherapeutic agents. Factors that have been shown to predict for poor mobilization include increasing numbers of cycles of prior chemotherapy, prior radiation therapy, and the presence of marrow metastasis.18-20 Fludarabine is particularly toxic to stem cells and this should be avoided in patients for whom a stem cell collection for autograft is planned. It has also been shown that there is a correlation between the number of circulating CD34+ cells and the probability of obtaining an adequate collection for transplant.21
Until recently poorly mobilizing patients had few options. However, an agent originally developed to treat HIV, plerixafor, has recently been shown to have significant activity in these patients. In contrast to G-CSF which needs multiple injections over several days a single dose of plerixafor mobilizes stem cells into the periphery beginning at 1 hour and peaking at 10 hours.22 In addition the quality of the stem cell graft mobilized by plerixafor may be superior. Compared to G-CSF mobilized cells, the plerixafor-mobilized cells were more primitive and therefore more quiescent and produced superior engraftment in both NOD/SCID mice and human recipients.23 The combination of G-CSF and plerixafor has also been studied and produces greater increases in CD34+ cells than with either agent alone.24
Standard collections of allogeneic peripheral blood stem cell (PBSC) involve 3 to 4 hours per apheresis procedure, during which approximately 10 L of blood are processed. At least two collections are usual, but large volumes of 25 to 30 L are more efficient and used increasingly to allow complete collections with a single procedure.25 Donor demographic and laboratory predictors such as platelet count and CD34+ mononuclear cell count can be used to customize the length of the collection procedure.26
As G-CSF is still the standard agent used, complications seen with stem cell mobilization are often related to this cytokine. Bone pain, headache, fatigue, insomnia, and gastrointestinal disturbances are usually mild and respond to administration of acetaminophen or NSAIDs. Spleen size increases in almost all individuals on G-CSF and this has been associated with splenic rupture. Donors should be advised to refrain from contact sports for a few weeks after the last mobilization.27 Vascular complications and citrate toxicity are not unlike those experienced in other long apheresis procedures (see below).
PBSC grafts are infused as fresh collections or stored frozen with the cryoprotectant dimethyl sulfoxide (DMSO) in liquid nitrogen. Thawed cells infused with DMSO may cause nausea, vomiting, fever, dyspnea, hypotension, and anaphylaxis. Reactions are dose dependent and may be lessened by prophylactic antihistamines. PBSCs carry the risk of transfusion-transmitted infectious agents and are tested in the same manner as are other blood components. However, given their highly specialized use and their life-saving potential, exceptions are made to donor selection criteria normally used for allogeneic blood collections, with the concurrence of the treating physician and the recipient.
Adequate cell dose for engraftment depends on whether the procedure is an autograft, a related, or an unrelated allograft. Cell dose, cell source, and patient characteristics are all important variables. The dose of stem cells for unrelated donors (National Marrow Donor Program) is 2 to 4 × 108 nucleated cells per kilogram of recipient weight, with 2 to 4 × 106 CD34+ cells per kilogram of recipient weight deemed as an adequate dose for transplantation and doses of greater than 5 × 106 CD34+ cells per kilogram of recipient weight associated with more rapid engraftment.28 Lower doses may be adequate in related donor settings, but engraftment of both leukocytes and platelets correlates with CD34 cell content.
Cord blood is being used increasingly as a stem cell source. Less graft-versus-host disease (GVHD) is seen as grafts have less alloreactivity even when mismatched as compared with PBSC or bone marrow grafts. In addition because mismatching is better tolerated there is a better chance of finding a suitable donor. However, because of lower numbers of progenitor cells, hematopoietic reconstitution is delayed and as a result recipients of umbilical cord transplants have a higher risk of developing fatal infections. Cells are obtained from the placenta during the third stage of delivery or postdelivery, with the consent of the mother, and stored in liquid nitrogen. The component volume is usually 50 to 100 mL and may be further reduced by removing red cells and plasma. The small volumes and yields of CD34+ progenitor cells currently make cord blood most suitable for children and smaller adults, although simultaneous infusion of two and even three cord blood units have resulted in successful engraftment for larger adults.29PBSCs stored in liquid nitrogen likely remain stable for many years, but maximum safe storage periods have not been determined. Recipients of minor mismatched cord blood seem less likely to make red cell alloantibodies than do recipients of mismatched marrow or PBSC.
Blood Derivatives
Derivatives or blood products are produced commercially by fractionation of plasma and include colloids such as albumin and plasma protein fraction, immune globulins, coagulation factor concentrates, and a variety of orphan proteins such as α-1-antitrypsin and antithrombin.
Prothrombin Complex Concentrate
PCCs are derived from pooled human plasma. They were initially developed for the prophylaxis and treatment of patients with factor IX deficiency. The two products available in the United States (Profilnine SD and Bebulin VH) are termed 3 factor-PCCs as they contain low levels of factor VII.
All PCCs contain the vitamin K dependent factors II, IX, and X while 4 factor-PCCs used in Europe contain higher levels of factor VII.
Thromboembolism is a potential adverse effect and may occur less in 3-factor than 4-factor products.30
Indications: Emergency treatment of bleeding due to overanticoagulation with warfarin. May be useful when volume overload with FFP a risk. Should always be used in combination with Vitamin K therapy.31
See Table 24.5 for more blood derivatives and Table 24.6 for coagulation factor preparations.
Rh Immune Globulin
Rh immune globulin (RhIg) is available in intramuscular (IM) form and intravenous (IV) form.
Indications: Prevention of alloimmunization of Rh-negative recipients exposed to Rh-positive RBC, immune thrombocytopenic purpura (ITP).
Prevention of Rh immunization in Rh-negative women with Rh-positive fetuses and subsequent HDN or after blood transfusion with Rh-positive blood.
Greater than 99% success in preventing Rh alloimmunization in pregnancy32; failure is usually because of missed or insufficient injections.
Treatment of ITP in Rh-positive patients only (intravenous RhIg).
Intramuscular RhIg is used in Rh-negative females of childbearing age after exposure to small- volume Rh-positive RBC (with platelet transfusions or the accidental transfusion of an Rh-positive unit of RBC). RhIg IV is used for large volume exposures.
Use of RhIg in Rh-negative males and females without childbearing potential is controversial but may protect from complications of future transfusions.
In a pregnancy where the mother is Rh negative and the father Rh positive, the fetus may be Rh positive and therefore there is a risk of Rh immunization of the mother. In these cases a prophylactic dose of 300 μg of anti-D is given at 28 weeks gestation.
A full dose containing 300 μg of anti-D to cover an exposure of 15 mL of Rh-positive RBC is also given:
To Rh negative women at risk of Rh immunization within 72 hours of delivery.
After amniocentesis and chorionic villus sampling, with manipulations such as external cephalic version, ectopic pregnancy, abortion, and abdominal trauma after 20 weeks gestation.
A minidose containing 50 μg of anti-D to cover an exposure of 2.5 mL of Rh-positive RBC can be given if these events occur before 12 weeks although 300 μg is often given as it is more readily available.
Erroneous transfusions:
RhIg dose should be calculated based on the RBC volume transfused.
The half-life of RhIg is 21 days. Additional RhIg should be administered in the following situations:
Expected ongoing risk of fetomaternal hemorrhage.
Nonobstetric cases with additional transfusion of products containing Rh-positive RBC 21 days or more after the last dose of RhIg.
RhIg should be given within 72 hours but if not feasible it should still be administered as soon as the need is recognized for up to 14 days. Some authorities maintain that it may be useful up to 28 days.33
Not indicated: Rh-positive individuals, previously immunized Rh-negative individuals, Rh-negative females with known Rh-negative fetuses or newborns, or in Rh-negative patients with ITP.
Derivative and Recombinant Coagulation Factors
Recombinant and plasma-derived coagulation factors provide a concentrated source of the desired factor for prevention and treatment of bleeding episodes in patients with factor deficiencies. Recombinant factors contain no other human-derived products and no risk of viral disease transmission (Table 24.6).
TRANSFUSION REACTIONS AND ADVERSE SEQUELAE
Any adverse response to blood component transfusion is considered a transfusion reaction. Most reactions occur at the beginning or during transfusion and are termed acute. Others, including development of alloantibodies, iron overload, and some parasitic and viral infections, do not become apparent for weeks, months, or years and are termed chronic.
Because most transfusion reactions occur within 15 minutes, close monitoring of vital signs and status at the beginning of the transfusion may prevent more severe reactions.
If a reaction is suspected, the infusion should be halted, the transfusion service notified, appropriate samples collected, and the patient monitored.
Transfusion reactions can be classified as hemolytic versus nonhemolytic and acute versus delayed. Hemolytic reactions may be immune or nonimmune-mediated (Table 24.7).
Acute Hemolytic Transfusion Reaction
Acute hemolytic transfusion reactions may be severe and fatal and may occur with as little as 10 mL of incompatible blood. Most result from ABO blood group incompatibility between patient plasma and donor RBC, and are usually the result of the incorrect transfusion of a unit (or several units) of blood intended for another patient.
Presentation: Fever, chills, flank/back pain, dyspnea, chest pain, anxiety which can progress to hypotension, renal failure, shock, and death if severe
Mechanism: ABO incompatibility resulting from destruction of transfused RBC by preformed, naturally occurring IgM anti-A and/or anti-B isohemagglutinins in the recipient’s plasma.
Intravascular hemolysis is caused by complement fixation by IgM antibodies.
Hemoglobinemia occurs followed by hemoglobinuria.
Complement activation promotes histamine and serotonin release which causes wheezing, chest pain or tightness and gastrointestinal symptoms.
Acute hemolysis results in anemia.
Cytokine release contributes to renal failure, hypotension, shock, and DIC.
Evaluation
Clerical check of component bag and compare with patient identification
Submit to the blood bank:
The infusion set, the implicated unit, and any units transfused within 4 hours of the reaction.
Blood specimens from the patient for repeat ABO group and Rh type determination, crossmatch, and DAT (usually positive); assessment of other parameters such as hematocrit (decreased), lactate dehydrogenase (increased), haptoglobin (decreased), and bilirubin levels (increased usually by 6 hours)1 as indices of hemolysis.
First posttransfusion-voided urine to examine for hemoglobinuria.
Transfusion reaction report detailing the events, signs/symptoms, and documenting the patient’s pretransfusion and posttransfusion vital signs.
Management: Mainly supportive, transfusion must be stopped and disconnected at the hub of the needle and intravenous access maintained with physiologic saline.
Support of blood pressure and renal blood flow with fluids and pressors if necessary, and induction of diuresis to maintain urine output at greater than 1 mL/kg/h. 6,34
Withhold further transfusion until the cause of the reaction is determined.
Coagulation status should be monitored and DIC treated if present.
Prevention: Meticulous clerical check of the blood unit and patient identification. In case of error in patient identification, immediate steps must be taken to insure that a second patient does not receive the wrong unit (companion error).
Hemolysis Associated with Passive Antibody Infusion
Severe acute hemolysis can occur if large volumes of ABO-incompatible plasma (usually group O FFP or apheresis platelets into group A patient) are infused.
Recognition and management of acute anemia is ordinarily sufficient.
Sickle Cell Hemolytic Transfusion Syndrome
Patients with sickle cell anemia are at increased risk from hemolytic transfusion reactions. A fall in Hb after transfusion of red cells is suggestive of the hyperhemolytic syndrome. This entity is poorly understood but occurs when both the patient’s and the transfused red cells are destroyed.1,35 Transfusion-associated hemolysis may mimic a severe posttransfusion pain crisis which is mediated by factors such as decreasing hemoglobin, complement activation, and increased oxygen consumption with fever. Stopping transfusion is imperative as additional transfusion may result in exacerbation of the syndrome. In the United States, inherent differences in RBC antigen phenotypes between patients with sickle cell anemia (almost exclusively of African descent) and the majority of blood donors (primarily non-African) place patients with sickle cell anemia at increased risk of alloantibody formation and immune hemolysis. In addition, patients with sickle cell disease are often chronically and heavily transfused. Extended red cell phenotyping of patients with sickle cell anemia in the early stages of transfusion therapy reduces the risk of alloimmunization.36,37
Delayed Hemolytic Transfusion Reaction
Delayed hemolytic transfusion reaction (DHTR) occurs within days, weeks, or even months after transfusion in patients who have been previously immunized by transfusion or by pregnancy (primary immunization). These reactions rarely, if ever, occur as a result of primary immunization and are usually a result of second transfusions. Because its manifestation may be mild and symptoms delayed in onset, DHTR may not be immediately recognized and this complication is likely underreported.34 Serious sequelae are rare. The importance of recognizing these reactions is to document antibody formation and prevent hemolytic reactions with future transfusions.
Presentation: Fever with or without chills, and symptoms of anemia. Jaundice may be present.
Subtle decrease in hemoglobin may be the only clinical manifestation.
DAT is usually positive.
Hemoglobinuria is rare because hemolysis is extravascular.
Mechanism: Repeat stimulation and accelerated (anamnestic) appearance of the antibody in a previously alloimmunized patient upon reexposure to the offending antigen.
Management: Close monitoring of the patient’s Hb for evidence of continuing hemolysis and supportive therapy.
Prevention: Future transfusions must be antigen-negative for the corresponding implicated antibody even if antibody is no longer detectable.
Notification of the patient to prevent future reactions (as by antibody card or bracelet).
Other Causes of Hemolysis
Other causes of hemolysis temporally associated with transfusion that may mimic hemolytic transfusion reactions include drug-induced hemolysis, mechanical and thermal hemolysis, and hemolysis related to bacterial contamination of the RBC unit.
Drug-induced hemolysis which may be either intra- or extravascular may present with anemia, positive DAT, elevated LDH and bilirubin.
Hemolysis may result from administration of blood with hypotonic solutions (D5W, hypotonic saline, distilled water) or medications.
Mechanical hemolysis may result from prosthetic heart valves and other intravascular devices and transfusion through small-bore catheters or with the use of roller pumps.
Thermal hemolysis results from exposure of red cells to cold (ice, temperatures below 1–6°C, use of unmonitored refrigerators) or to temperatures above 42°C (malfunction of blood warmers, or unmonitored unconventional blood warming methods); the DAT should be negative in these cases; some of these reactions have been fatal.
Anaphylactic Transfusion Reactions
Anaphylactic transfusion reactions usually occur at the start of transfusion when small amounts of blood containing plasma are transfused. Although rare, anaphylactic reactions may be rapidly fatal.
Presentation: Sudden onset of urticaria, flushing, chills, vomiting, diarrhea, initial hypertension followed by hypotension, angioedema, coughing, stridor, laryngeal edema, and progression to respiratory distress and shock. Fever is not a feature of anaphylaxis.
Mechanism: IgE-mediated response to transfused proteins.
IgA-deficient patients with antibodies to IgA are particularly susceptible to anaphylaxis on receiving plasma containing IgA.
Management: Discontinue transfusion and employ standard measures for anaphylaxis: Epinephrine, corticosteroids, circulatory support.
Anti-IgA or antibody to a subspecies must be demonstrated to confirm whether patient is IgA deficient.
Prevention: Usually not predictable. Subsequent transfusions to IgA-deficient patients should come from IgA-deficient donors.
If IgA-deficient blood components are not available, patients may benefit from receiving blood products that are depleted of plasma, such as washed RBC and platelets or frozen-deglycerolized RBC.
Transfusion-Related Acute Lung Injury
Transfusion-related acute lung injury (TRALI) is characterized by noncardiogenic pulmonary edema and is associated with transfusion of plasma-containing blood components. Previously believed to be underreported,34 it has an estimated frequency of between 1:1,300 and 1:5,000 transfusions and is the leading cause of transfusion-associated deaths reported to the FDA with a mortality rate of 6% to 10%.1,6
Presentation: Acute respiratory insufficiency, tachycardia, dyspnea, hypotension, oxygen desaturation (O2 saturation <90% on room air), chills, rigors, fever with 1°C to 2°C temperature increase, and a bilateral pulmonary infiltration by chest X-ray in the absence of heart failure or elevated central venous pressure, with no other causes of acute lung injury evident.34,38
Occurs during or within 6 hours (most commonly after 2 hours) of transfusion.
Hypoxemia may require intubation (70%–75% of cases).34
Symptoms subside rapidly; chest X-ray normal within 96 hours; clinical recovery in 48 to 96 hours in 80% of patients. 6
Mechanism: Reaction of antineutrophil antibodies and/or anti-HLA class I and II antibodies, usually donor derived, to corresponding recipient antigens; destruction occurs in the pulmonary vasculature and results in endothelial damage.
Multiparous females are more likely to be HLA/HNA alloimmunized, as are donors who have themselves been transfused.
Antibodies from the recipient against cells in the donor plasma implicated in approximately 5% of cases.
In 10% of cases no donor or recipient antibodies are identified.
A second possible pathophysiologic mechanism of TRALI is the “two-hit” theory, which suggests an interaction between primed pulmonary neutrophils in patients with underlying illness (in proinflammatory states) and biologically active response modifiers (lipids, cytokines) introduced by transfusion.39
Management: Discontinue transfusion and provide respiratory and circulatory supportive care; steroids and diuretics are not useful.
Prevention: A patient who has experienced TRALI is not necessarily at increased risk for development of TRALI with future transfusions, unless receiving blood from the same donor. Implicated donors are ordinarily deferred indefinitely. Many blood centers now draw plasma preferentially from male donors to reduce the risk from multiparous female donors.40
Transfusion-Associated Circulatory Overload
Transfusion-associated circulatory overload (TACO) can present in a similar fashion to TRALI but is much more commonly seen. Unlike TRALI, circulatory overload is associated with central venous pressure elevation and cardiac failure. Pulmonary edema in TACO is cardiogenic in origin and may result in the development or exacerbation of congestive heart failure. In the absence of other complicating factors, circulatory overload is rarely fatal. Children, the elderly, those with compromised cardiac, renal, or pulmonary function, and patients in states of plasma volume expansion (normovolemic chronic anemia, thalassemia major, and sickle cell disease) are at particular risk.6,34
Presentation: Cough, dyspnea, cyanosis, orthopnea, chest discomfort, rales, headache, distension of jugular veins, and tachycardia.
Management: Discontinue transfusion and administer supportive care (oxygen, diuresis, phlebotomy), if necessary.
Prevention: Patients at risk should receive smaller aliquots of blood infused at slower rates (1–4 mL/ kg/h) in as concentrated a form as possible.
Transfusion-Associated Graft-versus-Host Disease
Transfusion-associated GVHD (TA-GVHD) is a rare but severe adverse outcome of transfusion. Those at risk include the immunocompromised, patients with certain malignancies such as lymphoma, neuroblastoma, and sarcoma, patients receiving directed donations (from family members or relations), and premature infants. Patients with HIV and aplastic anemia do not need irradiated blood products1,6,34(see Table 24.4).
Presentation: Rash, diarrhea, hepatitis, mucositis, and pancytopenia; almost universally fatal with rare reports of survival.1,34
Mechanism: Immunocompetent lymphocytes from the donor engraft recognize the patient’s antigens as foreign and initiate an immune response.
Management: Supportive; no specific measures have proved effective. Prevention: Irradiation of blood components.
Irradiation dose of 2,500 cGy.
Leukoreduction does not prevent TA-GVHD.
Bacterial Contamination and Sepsis
The initial symptoms of bacterial contamination occur shortly after the start of transfusion and usually within 2 hours. These include chills and fevers. Note that temperature increase can be less marked in patients premedicated with antipyretics or receiving corticosteroids. In addition mild septic reactions may be initially obscured by underlying conditions that predispose the patient to fever or manifest similar signs and symptoms.6,34
Presentation: Rigors and shaking chills, fever, nausea, vomiting, abdominal cramp, bloody diarrhea, severe hypotension, and rapid progression to circulatory compromise, renal failure, shock, and DIC.
Not all contaminated blood products result in clinically detectable sepsis, and fewer yet are fatal.
Mechanism: Common sources of bacterial contamination are subclinical bacteremia in the donor or skin contaminants at the phlebotomy site.
Commonly implicated in RBC contamination are bacteria that survive the cold storage conditions, such as Yersinia and Pseudomonas.
Platelets stored at room temperature are the component most susceptible to bacterial growth.
Contamination occurs in approximately 1:5,000 collections, sepsis in 1:50,000 transfusions, and death in 1:500,000 transfusions. 41
More than half of bacterial contaminations of platelets are caused by skin flora, Staphylococci, Streptococci, Propionibacterium; many species are not implicated in serious transfusion reactions.6,34, 41
Currently, the residual risk of septic transfusion reactions from platelets is estimated to be more than twice as high for whole blood derived platelets, not tested by culture method, than for culture- negative apheresis platelets, 1:33,000 versus 1:75,000.42
The highest mortality is usually associated with blood components contaminated with endotoxinproducing gram-negative bacteria.
Evaluation and management: Transfusion must be stopped and broad spectrum antibiotics commenced.
All transfusion units and blood component bags transfused within 4 hours should be returned to the blood bank for culture.
Blood samples from both the blood component unit(s) and the patient should be sent for culture.
Prevention: Strict hygienic practice from collection to processing, storage, and administration of the component and transfusion of blood components within the allotted 4 hours.
Mild Allergic/Urticarial Transfusion Reactions
Allergic transfusion reactions are relatively common, do not generally progress to anaphylaxis, are rarely lethal, and do not necessarily recur with subsequent transfusions.
Presentation: Localized erythema, pruritus, flushing, and urticaria, usually near the IV site.
Severe urticaria and pruritus may be the initial signs of anaphylaxis.
Mechanism: Release of histamine and other anaphylotoxins.
Evaluation and management: Mild allergic reactions generally resolve when transfusion is temporarily stopped, and symptoms improve with administration of oral or parenteral antihistamines.
Mild allergic reactions (hives only): Transfusion with the same unit may be resumed, at a slower rate and with close monitoring of the patient.
Transfusion reaction evaluation generally not necessary.
Prevention: Mild allergic reactions are considered atopic reactions and generally unpredictable.
No method to prescreen for all possible offending antigens.
Antihistamines are effective in treating, but not in preventing, allergic reactions.
Posttransfusion Purpura
Posttransfusion purpura (PTP) is a profound thrombocytopenia that may occur after transfusion with any blood component but is usually associated with transfusion of red cells or whole blood.
Presentation: Abrupt decline in the platelet count within days to 2 to 3 weeks posttransfusion (mean 9 days).6
Usually self-limiting: resolves within 2 to 3 weeks without treatment.
Mechanism: Not well understood; antibodies against platelet-specific antigens to which the patient may have become sensitized as a result of pregnancy or prior transfusion destroy both transfused and autologous platelets (innocent bystander effect).
Most commonly anti-human platelet antigen 1a (HPA-1a).
Management: IVIG is the current treatment of choice.
Although PTP almost never recurs antigen-negative components should be transfused in patients with previously documented PTP.
Family members provide a good source of donors if antigen-negative blood is otherwise not available.
Severe PTP that does not resolve spontaneously and if refractory to high-dose IVIG may respond to plasmapheresis. 1,34
Hypotension Associated with Transfusion
Mechanism: Transient isolated hypotension that resolves after discontinuation of transfusion may be caused by activation of bradykinin and is associated with use of bedside leukoreduction filters and apheresis procedures (especially with albumin replacement).34
Patients receiving ACE inhibitors are at particular risk since ACE inhibitors block normal metabolism of bradykinin.
Evaluation and Management: Severe transfusion reactions such as anaphylaxis, acute hemolytic transfusion reaction, TRALI, and bacterial contamination (sepsis) must be excluded.
Prevention: Avoid bedside leukoreduction (especially for patients taking ACE inhibitors).
Febrile Nonhemolytic Transfusion Reaction
Febrile nonhemolytic transfusion reactions (FNHTR) are defined by a greater than 1°C increase in temperature for which no other cause is identifiable. FNHTR is a diagnosis of exclusion, made after consideration of acute hemolytic transfusion reaction, TRALI, and sepsis and determination that the symptoms are not related to the patient’s underlying medical condition or medications. The incidence of FNHTR varies among patient populations and depends on the age and type of blood component and a variety of donor and recipient factors. Platelets are more likely to be implicated than are RBC or FFP, and older blood components more than fresh, leukocyte-reduced components (since cytokines accumulate during storage). The incidence is higher in patients who have received multiple transfusions.34
Presentation: Chills, fever, rigors which may be preceded by headache, and nausea; the patient may also experience tachycardia, tachypnea, and general discomfort.
Patients who sustain significant fever with transfusion are likely to have repeated reactions.
Mechanism: Interaction of antibodies in the recipient against donor leukocytes or platelets and subsequent cytokine release; accumulated cytokines in blood component bag during storage that are passively transferred from the donor to the recipient during transfusion.
Evaluation and management: Same as with a hemolytic reaction.
Antipyretics may be administered.
Prevention: Prestorage leukoreduction, removal of plasma in extreme situations, and premedication with antipyretics.
Hemosiderosis
Hemosiderosis or iron overload occurs in chronically transfused patients (usually a cumulative dose of 50–100 red cell transfusions).
Presentation: Classical symptoms rarely seen nowadays but include “bronzing” of skin, hepatomegaly, hepatic fibrosis and malfunction, diabetes and other endocrine gland dysfunction, and cardiac failure.
Mechanism: Accumulation of iron in the skin, liver, heart, and endocrine organs
Evaluation and management: Iron studies and iron chelation or phlebotomy when appropriate. Prevention: Consider chelation for more than 50 unit red cell burden; red cell exchange using apheresis helps delay iron accumulation in patients with sickle cell disease.6
Transfusion-Transmitted Infections
Current testing of donor blood prior to release of blood components includes the following:
Antibodies to human immunodeficiency virus (HIV) types 1 and 2 (anti-HIV-1/2); hepatitis C virus (HCV) (anti-HCV); hepatitis B core antigen (anti-HBc); human lymphotrophic virus types I and II (anti-human T-cell leukemia virus [HTLV] I/II); Treponema pallidum.
Surface antigen: Hepatitis B surface antigen (HBsAg).
Nucleic acid testing (NAT) for HIV; HCV; West Nile virus (WNV).
With current mandated testing, the estimated risk of transmission of viral infections per transfusion is reported in Table 24.8.42,43 Blood is also tested by enzyme-linked immunoassay for the detection Trypanosoma cruzi parasite, the causative agent for Chagas disease.
Other infectious agents and diseases transmissible by transfusion44,45 for which the blood supply is not currently routinely tested include the following:
Hepatitis A virus, parvovirus B19, and dengue virus
Parasitic diseases, not as common in the United States, including malaria, babesiosis, and leishmaniasis
The protozoal disease toxoplasmosis which affects mainly immunocompromised patients
Prions (protein particles) responsible for the transmission of variant Creutzfeldt-Jakob disease (vCJD). 46
Alternatives to Allogeneic Blood Transfusion
Alternatives to the use of blood component therapy are available and may be particularly useful for bleeding patients who refuse allogeneic blood component transfusions (usually for religious beliefs) or bleeding patients unresponsive to appropriate transfusion therapy.
Patients with religious concerns about blood transfusion must be informed of any human-derived contents in products that may be administered, allowing them to make an informed decision.
Examples of alternatives to allogeneic blood transfusion6,47 are listed in Table 24.9.
Indications for use of some pharmaceutical hemostatic agents1,48 are summarized in Table 24.10.
Massive Transfusion
Massive transfusion is the administration of blood components over a 24-hour period in amounts that equal or exceed the total blood volume of the patient (10 or more units of whole blood or 20 units of packed RBC in an adult). After transfusion of one or more blood volumes, an abbreviated RBC cross-match (see general concepts) is performed to provide RBC more rapidly. Group O, Rh-negative, or Rh-positive blood (acceptable in male patients or postmenopausal females) may be released initially and once a specimen is received by the transfusion lab ABO-compatible blood can be provided.
Adequate intravascular blood volume and blood pressure may be maintained initially with colloids (albumin, plasma protein fraction) or crystalloids (lactated Ringer solution or normal saline).
Transfusion of packed RBC may become necessary after a loss of more than 25%–30% of blood volume, depending on the rate of blood loss, tissue perfusion, and oxygenation status of the patient. 49
Transfusion of blood components based on fixed ratios or algorithms should be avoided.
Adverse Sequelae of Massive Transfusion
Dilution and/or consumption of hemostatic constituents of blood. Platelet count, prothrombin time (PT), partial thromboplastin time (PTT), and fibrinogen levels should be determined frequently.
Replacement therapy is warranted if platelet count is less than 50, PT/PTT greater than 1.5, and fibrinogen concentration less than 100 mg/dL.
Hypothermia, acidosis, hypocalcemia, and other biochemical disturbances may occur and electrolytes, particularly potassium and calcium, should be monitored. 1,49
Hypocalcemia secondary to citrate accumulation may occur when large volumes of blood are administered at rapid rates (more than 100 mL/min), especially in the presence of liver and renal dysfunction. 1,49
Disseminated Intravascular Coagulation
DIC probably complicates massive transfusion less often than suspected, but DIC is associated with shock, independent of blood loss or transfusion.
Laboratory coagulation test results are consistent with a consumptive coagulopathy.
Treatment is correction of the underlying disorder while transfusion therapy is supportive.
Administer cryoprecipitate when fibrinogen levels are below 80 to 100 mg/dL.
Other components, such as platelets may be necessary, especially if bleeding is severe.
If multiple factors are consumed, plasma factor levels of above 30% can be achieved with an FFP dose of 10 to 20 mL/kg. 1,49
IMMUNOHEMATOLOGIC DISORDERS
Hemolytic Disease of the Newborn
Hemolytic Disease of the Newborn (HDN) is the destruction of fetal erythrocytes by maternal IgG antibodies that cross the placenta and react with a paternally derived antigen present on the fetal RBC. Although traditionally associated with Rh antibodies (anti-Rh D), other antibodies including anti-A, anti-B, and anti-K:1 have been implicated and may cause significant HDN.
Mild cases: The newborn is asymptomatic and laboratory findings of a positive DAT and mild hyperbilirubinemia are the only abnormalities.
Severe cases: May result in intrauterine death (hydrops fetalis, erythroblastosis fetalis). There is a high risk of kernicterus caused by high unconjugated bilirubin.
Treatment: Intrauterine RBC transfusion (in severe cases) using antigen compatible (with the mother’s antibody), irradiated, CMV-negative, sickle-negative RBC suspended in 5% albumin or FFP.
Usually a two-blood-volume red cell exchange removes approximately 25% of excess bilirubin, provides albumin to which excess bilirubin can bind, and removes antibody and approximately 70% of RBC coated with antibody.
Additional exchange transfusions may be necessary if level of bilirubin continues to rise.
Neonatal Alloimmune Thrombocytopenia and Maternal Immune Thrombocytopenic Purpura
Neonatal Alloimmune Thrombocytopenia
Neonatal alloimmune thrombocytopenia (NAIT) is the destruction of platelets that carry paternally derived antigens by maternal antibodies that cross the placenta. As with HDN, NAIT may vary in severity
from very mild and asymptomatic thrombocytopenia to life-threatening bleeding, and it may occur in utero or in the neonatal period. The vast majority of NAIT is associated with antibody (IgG) against the common platelet antigen HPA-1a (PLA1), especially in the presence of HLA DRw52a phenotype.1
NAIT is usually self-limiting and resolves within 2 to 3 weeks. If NAIT is suspected, often as a result of a previously affected pregnancy, cordocentesis to determine platelet counts may be performed in conjunction with administration of compatible platelets (maternal platelets or platelets known to be negative for the implicated antigen).
In utero NAIT: IVIG is given with or without weekly corticosteroid administration to the mother (1 g/kg) until delivery.
If there is high risk of intracranial hemorrhage, platelet transfusion is performed immediately prior to delivery.
When compatible platelets are unavailable, high-dose IVIG has been administered to the neonate with variable effectiveness.
An increase in platelet counts within 24 to 48 hours may be seen in patients who respond to IVIG.6
Maternal Immune Thrombocytopenic Purpura
In maternal ITP, antibodies against maternal platelets can cross the placenta and cause thrombocytopenia in the fetus.
Degree of thrombocytopenia is milder than that associated with NAIT with a lower risk of fetal or neonatal intracranial hemorrhage.
Maternal platelets and random donor platelets are generally not required but may be needed in about 44% of newborns. 50
IVIG may also be beneficial.
Maternal ITP usually resolves in days to weeks (upon clearance of maternal antibodies from the neonate’s circulation).
Autoimmune Hemolytic Anemias
AIHA are characterized by the presence of antibodies against the individual’s own RBC antigens (autoantibodies), resulting in accelerated destruction of RBC. AIHA may be associated with autoimmune disorders, infections, medications or malignancies, or it may be primary. The laboratory hallmark is the positive DAT, indicating the presence of antibody or complement-coated red cells. Antibody may also be present in the serum such that positive DAT and IAT may coexist, making identification of underlying alloantibodies and compatibility testing difficult.
Warm Autoimmune Hemolytic Anemia
The majority of AIHA are caused by warm reacting antibodies. The implicated antibody is usually IgG and reacts with all cells, although occasionally a warm autoantibody will appear to have specificity against Rh antigens and several others. Patients with compensated warm AIHA require no specific treatment but should be investigated for an underlying condition such as systemic lupus erythematosus or a lymphoproliferative disorder. In children, viral illness may be accompanied by transient AIHA. Medications, particularly purine nucleoside analogues, are commonly associated with warm AIHA. Warm-reacting autoantibodies may be present only as a laboratory finding, or they may cause severe, even life-threatening hemolysis; these antibodies react optimally at 37°C in vitro. Patients are often totally asymptomatic, but may present with fatigue, jaundice, or mild anemia. Moderate splenomegaly occurs in about one-third to one-half of the cases and hepatomegaly in one-third of the patients. Hemolysis is usually not severe and is mainly extravascular.51
Laboratory findings include a positive DAT, spherocytes on the blood smear, elevated unconjugated bilirubin and LDH as indices of cell turnover, and a high reticulocyte count. Rarely, reticulocytopenia may be seen, either because of inadequate bone marrow response or because the autoantibody reacts with red cell precursors as well as with mature cells.
Red cell alloantibodies as a result of previous transfusions or pregnancies, found in approximately one-third of patients with AIHA, are capable of causing severe hemolytic transfusion reactions. Broadly reactive autoantibody may mask underlying alloantibodies and make procurement of compatible blood difficult.
Occasionally hemolysis may result in severe symptomatic anemia. Transfusion should not be delayed even when compatible blood cannot be obtained. The term “least incompatible” has not been adequately defined, does not correlate to clinical events, and would be best abolished.51
Oral glucocorticoids (prednisone at 1 mg/kg/day) are the current standard of care and about 50% of patients will respond. Splenectomy is effective in approximately half of those who are refractory to steroids. Immunosuppressive agents and IVIG may benefit selected patients.51 Refractory AIHA, especially when associated with lymphoproliferative disease, may respond to the monoclonal antibody rituximab (see below).
Cold Agglutinin Syndrome
Cold-reacting antibodies are common and usually of no significance, but some cold agglutinins, especially those with very high titer at 4°C but broad thermal amplitude (reactivity up to 30°C) may result in cold agglutinin syndrome (cold hemagglutinin disease). IgM is the immune globulin classically implicated and the DAT is almost always positive for C3d alone. Cold agglutinin syndrome may be primary (idiopathic) or secondary, often to a viral infection or lymphoproliferative disorder. Acute cold agglutinin syndrome may be associated with Mycoplasma pneumoniae and Epstein-Barr virus, is seen mostly in children and young adults, and tends to be transient and self-limited. Chronic cold agglutinin syndrome is most often seen in the elderly and may be associated with lymphoma, chronic lymphocytic leukemia, and Waldenstrom macroglobulinemia. Patients may present with acrocyanosis and hematuria precipitated by cold, and/or severe pain in the nose, ears, and distal extremities upon cold exposure. Severe anemia is rare in the chronic form.
Transfusion is rarely necessary, but, when performed, the typing specimen must be kept at body temperature from the time of phlebotomy through the testing procedure. Up to 50% of transfused cells may be destroyed by autoantibodies of the patient even when blood warmers are used.
Treatment with corticosteroids and splenectomy is not effective, and most patients do well simply by avoiding exposure to the cold. Rituximab, the anti-CD20 monoclonal antibody, appeared useful when administered as four weekly infusions in a small number of patients.52
Paroxysmal Cold Hemoglobinuria
Paroxysmal cold hemoglobinuria (PCH) is a rare form of AIHA that results from a biphasic IgG antibody (Donath-Landsteiner antibody). Originally associated with untreated syphilis, it is now found most often with viral infections in children. The Donath-Landsteiner antibody binds to the RBC at cold temperatures and causes intravascular hemolysis as complement is fixed at warmer temperatures, accounting for the paroxysms of hemoglobinuria. Anemia associated with PCH is usually transient and self-limiting over 2 to 3 weeks. If transfusion support becomes necessary, crossmatch-compatible blood may be found if the antibody is not reactive at temperatures above 4°C. Unavailability of compatible RBC should not preclude transfusion in life-threatening anemia associated with hemolysis, despite shortened survival of the transfused RBC.1,6,51
Therapeutic Apheresis in the Management of Immunohematologic Disorders
Apheresis is the process by which selected components or substances in blood are removed from the circulation and the remainder of the blood returned to the patient. Apheresis is used to collect routine blood components (platelets, plasma, stem cells) from donors for transfusion. It also has therapeutic utility in many disorders where a pathologic substance is found in the blood. It is also used to remove an excess of cells, normal or abnormal, in the blood, known as cytapheresis. See Table 24.11 for commonly accepted indications for therapeutic apheresis for hematologic disorders endorsed by the American Society for Apheresis (ASFA).53
The kinetics of most intravascular substances indicate that exchange of 1 to 1.5 plasma volumes results in the highest efficiency removal with progressively decreased efficiency and added toxicity with each additional consecutive exchange.
The volume of blood processed in order to attain the desired apheresis effect depends on the nature of the specific component, including its intravascular distribution and concentration in the particular patient.
Table 24.11 Recommendation for Therapeutic Apheresis in Hematologic Disorders
Category I: Accepted as Standard First-line or Primary Therapy
Babesiosis-severe (red cell exchange)
Cryoglobulinemia (plasma exchange)
Cutaneous T-cell lymphoma (photopheresis)
Hyperviscosity in monoclonal gammopathies (plasma exchange)
Hyperleukocytosis (cytapheresis)
Sickle cell disease with acute stroke (red cell exchange)
Thrombotic thrombocytopenic purpura (plasma exchange)
Polyneuropathy with IgM, with or without Waldenstrom macroglobulinemia (plasma exchange)
Hemolytic uremic syndrome—atypical (plasma exchange)
Category II: Generally Accepted as Adjunctive or Supportive Therapy
ABO-incompatible hematopoietic progenitor cell/marrow transplantation (plasma exchange recipient)
Graft-versus-host disease—skin (photopheresis)
Malaria—severe (red cell exchange)
Myeloma with acute renal failure (plasma exchange)
Red cell alloimmunization in pregnancy* (plasma exchange)
Sickle cell disease—primary/secondary prophylaxis/iron overload prevention (red cell exchange)
Thrombocytosis—symptomatic (cytapheresis)
Pure red blood cell aplasia (plasma exchange)
Category III: Optimal Role of Apheresis Therapy Not Established
Aplastic anemia (plasma exchange)
Erythrocytosis or polycythemia vera (phlebotomy/cytaphersis)
Warm autoimmune hemolytic anemia (plasma exchange)
Graft-versus-host disease—nonskin (photopheresis)
Multiple myeloma with polyneuropathy (plasma exchange)
Thrombocytosis—prophylactic (cytapheresis)
Posttransfusion purpura (plasma exchange)
*If fetus <20 wk gestation and previous severely affected pregnancy.
Adapted from Szczepiorkowski ZM,Winters JL, Bandarenko N, et al. Guidelines on the use of therapeutic apheresis in clinical practice-Evidence-based approach from the Apheresis Applications Committee of the American Society for Apheresis. J Clin Apher. 2010;25(3):83-177.
The patient’s total blood volume determines the safe extracorporeal blood volume (which should not exceed 15% of blood volume).
Small patients may require that the machine be primed with saline or blood.
Apheresis is generally safe, especially for normal component donors. Complications mainly relate to vascular access, hemodynamic changes (especially for patients with cardiovascular disease), and a variable loss of blood components. Risks associated with apheresis are usually associated with a patient’s underlying disease.
Plasma exchange may result in a 30% or more decrease in platelet counts.54
Platelet transfusion may be required for patients with low platelet counts and hemostatic problems.
Cellular blood component counts return to normal after a few days and proteins and electrolytes re-equilibrate within hours, although fibrinogen may remain below baseline levels after 72 hours. 55
Hypotension may occur as a result of volume shifts and bradykinin activation from blood contact with plastic6,56; withhold ACE inhibitors, which potentiate this effect, from patients for 24 to 48 hours prior to an apheresis procedure.
Plasma exchange may reduce blood levels of certain medications, especially those bound to plasma proteins or those with a long plasma half-life. 56
Citrate is used to prevent coagulation of blood in the circuit and may result in citrate toxicity: binding of calcium, decreased levels of ionized calcium, and potentially symptomatic hypocalcemia.
Hypocalcemia may present with mild perioral tingling and discomfort, chest tightness, and tetany in severe cases; if symptoms do not subside with adjustment of citrate and whole blood flow rates, administration of oral calcium (as chewable tablets) or intravenous calcium gluconate replace the bound calcium and prevent the accompanying syndromes. 57
Thrombocytapheresis
Increased platelet counts, particularly in myeloproliferative disorders in which platelets are also qualitatively abnormal, may be associated with bleeding or thrombosis.
Patients who are bleeding (e.g., with chronic myelogenous leukemia [CML]) may obtain immediate benefit from therapeutic cytapheresis. Generally plateletpheresis is a first-line therapy for thrombocytosis (platelet counts greater than 500,000/μL) in symptomatic patients.
Each procedure will lower the count 30% to 50%.
Cytoreductive chemotherapy should be initiated simultaneously, since plateletpheresis is not effective long term. 53,56
Leukocytapheresis (Leukapheresis)
Malignant leukocytosis or hyperleukocytosis (immature white blood cell counts of greater than 100,000/μL), in association with some leukemias, can result in leukostasis in the central nervous system, kidneys, and lungs. Symptoms may occur with rapidly rising blast counts less than 100,000/μL, especially in AML and CML.
Changes in mentation, dizziness, blurred vision, hypoxia, or respiratory symptoms constitute a medical emergency where rapid cytoreduction is imperative.
Therapeutic leukapheresis can reduce the leukocyte count by 30% to 50% in hours.
Symptoms may abate promptly.
Reduction of the white cell count permits cytoreductive chemotherapy and reduces the risk of developing tumor lysis syndrome.
Chemotherapy with hydroxyurea (if myeloid malignancy) or a similar agent should be initiated concurrently since repeated leukocytapheresis may not control hyperleukocytosis.
Photopheresis (Extracorporeal Photochemotherapy)
Photopheresis is the separation of the patient’s leukocytes by apheresis for extracorporeal treatment with the chemotherapeutic agent 8-methoxy-psoralen (8-MOP) and photoactivation by ultraviolet A (UVA) light for subsequent reinfusion to the patient.
It has some efficacy in the treatment of refractory cutaneous T-cell lymphoma, allograft rejection, refractory acute and chronic GVHD, scleroderma, and other autoimmune diseases.
Mechanism of action is not fully understood; possibly related to apoptosis of pathogenic T lymphocytes and antigen-presenting cells or anti-idiotype cytotoxic T-cell response 1,56
Use of 8-MOP is contraindicated in patients with light-sensitive disorders such as xeroderma pigmentosa, albinism, and certain porphyrias. 56
Erythrocytapheresis/Red Cell Exchange
Red cell exchange involves the removal of abnormal red cells.
Patient’s RBC are replaced with normal donor RBC in patients with sickle cell disease.
Erythrocytapheresis may be used to reduce red cell mass acutely in symptomatic (visual disturbances, confusion, lethargy, hemorrhage, threatened stroke, thrombosis of abdominal vasculature) patients with excessive polycythemia. 53,56
In Polycythemia Rubra Vera (PRV) saline or colloid volume replacement is administered to maintain isovolemia.
Red Cell Exchange and Sickle Cell Anemia
Red cell exchange may be used acutely to treat some complications of sickle cell disease53 including acute chest syndrome, stroke, retinal infarction, priapism, and hepatic crisis, or as protracted or chronic
treatment for the prevention of complications such as stroke and recurrent severe painful crises, and for reduction of iron overload secondary to transfusion.56
In the perioperative setting, simple transfusion or a single red cell exchange prevents morbidity associated with sickle cell disease.
The goal is to achieve hemoglobin S of less than 30%.
Transfusion and exchange have been used to treat sickle complications during pregnancy but routine use is not warranted. Exchange transfusion can raise hemoglobin A to levels difficult to achieve with simple transfusion and may benefit patients in the third trimester for preeclampsia, sepsis, and preoperative management. 56
Red Cell Exchange and Parasitemia
Red cell exchange has been used as antiparasitic treatment in malaria to decrease the circulating parasite load when it exceeds 5%.58
Plasmapheresis
Plasmapheresis may be used to collect plasma for transfusion or manufacturing of plasma derivatives, or to remove undesirable substances from the circulation. Colloids or saline (plasma with TTP) are administered to maintain isovolemia. See Tables 24.11 and 24.12 for common indications for therapeutic plasmapheresis.53
Thrombotic Microangiopathies
TTP and hemolytic uremic syndrome (HUS) belong to a spectrum of thrombotic microangiopathies: TTP may be associated with prominent neurologic symptoms; HUS presents with a more prominent renal component. Characteristic findings of TTP include fever, renal impairment, neurologic symptoms such as change in mental status, seizures, or coma, thrombocytopenia (platelet counts usually less than 30,000/μL), and microangiopathic hemolytic anemia with schistocytes.
TTP results from the accumulation of ultra-large von Willebrand factor multimers caused by congenital absence of or inhibitory antibodies to the vWF-cleaving metalloprotease ADAMTS13.1,56 When TTP and HUS-like syndromes are associated with immunosuppressive agents (typically vinca alkaloids, mitomycin, bleomycin, BL22, cisplatin, tacrolimus, and cyclosporin A), post bone marrow transplant or cancer they do not respond well to therapeutic plasma exchange (TPE).
TPE is first-line therapy for the treatment of TTP and generally not effective for typical HUS.
TPE should be performed as soon as TTP is suspected.
The effectiveness of TPE in TTP depends on the removal of ultra-large vWF multimers and reduction of the IgG antibodies against vWF-cleaving protease.
Plasma (FFP) is the fluid replacement of choice in TPE for TTP and also replaces the vWF-cleaving protease.
TPE is often done daily, then tapered until platelet counts stabilize at more than 100,000/μL for 2 consecutive days.
Response should be monitored by clinical assessment and laboratory measurements (platelet count, LDH, extent of schistocytosis).
Platelet transfusion is generally discouraged as this is thought to potentially precipitate thrombosis. This dogma has recently been challenged.11 However, platelet transfusion may be necessary in the event of life-threatening hemorrhage.6
Dysproteinemias
Complications of paraproteinemias of multiple myeloma, Waldenstrom macroglobulinemia, and cryoglobulinemia respond to TPE.
Hyperviscosity syndrome with mental status changes, mucosal and gastrointestinal bleeding, retinopathy, and hypervolemia constitutes a medical emergency.
Hyperviscosity responds to even small volume exchanges, but procedures need to be repeated until the paraprotein is controlled with chemotherapy. 56
References
Suggested Reading
Gottschall J. Blood Transfusion Therapy: A Physician’s Handbook. 10th ed. Bethesda, MD: AABB Press; 2011.
McLeod BC. Therapeutic Apheresis: A Physician’s Handbook. 3rd ed. Bethesda, MD: AABB Press; 2010.
Osby MA, Saxena S, Nelson J, et al. Safe handling and administration of blood components: review of practical concepts. Arch Pathol Lab Med. 2007;131:690-694.
Roseff SD. Pediatric Transfusion: A Physician’s Handbook. 3rd ed. Bethesda, MD: AABB Press; 2009.
Snyder EL, Haley NR, eds. Cellular Therapy: A Physician’s Handbook. Bethesda, MD: AABB Press; 2004.
Szczepiorkowski ZM, Winters JL, Bandarenko N, et al. Guidelines on the use of therapeutic apheresis in clinical practice-Evidence-based approach from the apheresis applications committee of the American Society for Apheresis. J Clin Apher. 2010;25(3):83-177.
Zou S, Dorsay KA, Notari EP, et al. Prevalence, incidence, and residual risk of human immunodeficiency virus and hepatitis C virus infections among United States blooddonors since the introduction of nucleic acid testing. Transfusion. 2010;50:1495-1504.
Zou S, Stramer SL, Notari EP, et al. Current incidence and residual risk of Hepatitis B infection among blood donors in the United States. Transfusion. 2009;49(suppl 2):1S-235S.