Chapter 118: Transfusion Therapy and Biology¶
Chapter 355 | Part 12: Endocrinology
KEY CLINICAL POINTS¶
- Blood group antigens (ABO, Rh, Kell, MNS, etc.) and antibodies are critical for transfusion compatibility; mismatched transfusions can cause hemolysis, TRALI, or GVHD.
- Leukocyte-reduced blood components reduce febrile nonhemolytic transfusion reactions (FNHTR) and alloimmunization.
- Transfusion-related acute lung injury (TRALI) is a leading cause of transfusion-related mortality, mediated by HLA or HNA antibodies in donor plasma.
- Iron overload from frequent transfusions can cause cardiac, hepatic, and endocrine dysfunction; chelation therapy is essential in severe cases.
- Pathogen reduction technologies and donor screening are vital to prevent transfusion-transmitted infections (e.g., HIV, HBV, HCV, CMV).
1. DEFINITION & OVERVIEW¶
Transfusion therapy involves the use of blood components (red blood cells, platelets, plasma) to treat anemia, hemorrhage, and bleeding disorders. Blood group antigens (e.g., ABO, Rh) and antibodies (anti-RBC, anti-HLA, anti-HPA) mediate immune responses, leading to hemolysis, fever, or transfusion-related complications. Blood components are processed to ensure safety, efficacy, and compatibility.
Table 118-1: Blood Components: Collection and Manufacturing Processes¶
| Component | Processing | Rationale | Volume | Storage |
|---|---|---|---|---|
| RBCC | Leukocyte reduction | Reduce FNHTR, alloimmunization | 250–300 mL | 4°C (25–42 days) |
| PC | Suspension in PAS | Reduce fever, chills | 100–700 mL | 20–24°C (3–7 days) |
| Plasma | Cryopreservation | Extend shelf-life | 200–300 mL | -18°C (1–2 years) |
1.1 Blood Components¶
Blood components include red blood cell concentrates (RBCCs), platelet concentrates (PCs), and plasma. Leukocyte reduction, irradiation, and pathogen reduction are standard processing steps to minimize adverse reactions. Storage conditions (2-4°C, -18°C) and shelf-life vary by component.
1.2 Blood Group Systems¶
The ABO system (A, B, AB, O) and Rh system (D, C, E, c, e) are most clinically significant. Other systems (Kell, MNS, Duffy, Kidd) may also cause alloimmunization. Compatibility testing ensures safe transfusion.
2. EPIDEMIOLOGY¶
Transfusion reactions are common, with ~300/10 I transfusions associated with FNHTR. TRALI occurs in 0.5–10/10 I transfusions. Iron overload affects ~10–20% of patients with chronic anemia. Transfusion-transmitted infections (e.g., HIV, HBV) are rare due to screening but remain a risk in high-risk populations.
2.1 Risk Factors¶
Risk factors include prior transfusions, pregnancy, immunosuppression, and rare blood types. Neonates and elderly patients are more susceptible to transfusion-related complications.
3. ETIOLOGY & PATHOPHYSIOLOGY¶
Transfusion reactions arise from immune (alloantibodies, autoantibodies) or nonimmune (storage lesions, bacterial contamination) mechanisms. Hemolysis occurs via complement activation (MAC formation) or phagocytosis. TRALI is mediated by donor HLA or HNA antibodies. Iron overload results from cumulative iron deposition in tissues.
4. CLINICAL FEATURES¶
Acute hemolytic reactions present with fever, hemoglobinuria, hypotension, and DIC. TRALI manifests as hypoxia and pulmonary edema. FNHTR causes fever and chills. Posttransfusion purpura (PTP) presents with thrombocytopenia and bleeding 5–12 days post-transfusion.
4.1 Hemolytic Reactions¶
Acute hemolysis (within 24 h) vs delayed (3–10 days). Intravascular vs extravascular hemolysis. Clinical features include jaundice, hemoglobinuria, and anemia.
5. DIFFERENTIAL DIAGNOSIS¶
Differential diagnoses for transfusion reactions include sepsis, hemolysis from other causes (e.g., hemolytic anemia), and drug reactions. TRALI must be distinguished from circulatory overload and pneumonia.
6. INVESTIGATIONS & DIAGNOSIS¶
Diagnosis involves direct/indirect Coombs tests, DAT, and plasma/serum testing for antibodies. Blood cultures and nucleic acid amplification tests (NAT) detect pathogens. Flow cytometry and molecular typing (e.g., DNA sequencing) identify rare blood group phenotypes.
Table 118-2: ABO Blood Groups and Antibodies¶
| Genotype | Antibodies | Transfusion Compatibility |
|---|---|---|
| A/A or A/O | Anti-B | A or O |
| B/B or B/O | Anti-A | B or O |
| A/B | None | A, B, AB |
6.1 Laboratory Tests¶
Direct antiglobulin test (DAT), indirect antiglobulin test (IAT), hemoglobin electrophoresis, and flow cytometry for HLA or HNA antibodies.
7. MANAGEMENT & TREATMENT¶
Management includes stopping transfusion, supportive care (fluids, diuretics), and specific therapies (e.g., corticosteroids for hemolysis, plasma exchange for severe reactions). Iron chelation (deferoxamine) is used for overload. Pathogen reduction and leukocyte filtration prevent infections.
7.1 Hemolytic Reactions¶
Supportive care, corticosteroids, and plasma exchange. Avoid further transfusions until antibody clearance. Monitor for DIC and renal failure.
8. PROGNOSIS & COMPLICATIONS¶
Prognosis varies: TRALI is often fatal, while FNHTR is self-limiting. Chronic transfusion-related iron overload can lead to organ failure. Alloimmunization may cause refractoriness to platelet transfusions.
8.1 Long-term Risks¶
Iron overload, cardiovascular disease, and endocrine dysfunction. Neonates and elderly patients face higher risks of complications.
9. SPECIAL CONSIDERATIONS¶
Pregnancy: Anti-D immunization in Rh-negative women. Pediatrics: Neonatal alloimmune thrombocytopenia (NAIT). Elderly: Increased risk of TACO and infections. Rare blood types require specialized donor programs.
9.1 Pregnancy¶
Rh-negative women receiving Rh-positive blood develop anti-D antibodies, risking hemolytic disease of the fetus and newborn (HDFN). Anti-D immunoglobulin prophylaxis is critical.
10. KEY POINTS & CLINICAL PEARLS¶
- Always confirm ABO/Rh compatibility before transfusion. 2. Leukocyte-reduced components reduce FNHTR and alloimmunization. 3. TRALI is a leading cause of transfusion-related mortality; avoid donor plasma with anti-HLA antibodies. 4. Iron overload requires chelation therapy. 5. Pathogen reduction technologies minimize infectious risks.