Blood Transfusion Guide: ABO, Reactions, OmpathStudy

COMPREHENSIVE REVISION NOTES BATCH 3 Topics 15 – 18 (Final) --- TOPIC 15: BLOOD GROUPS & TRANSFUSION COMPATIBILITY Definition: Blood typing based on antigens (A, B, Rh/D) present on RBC surface Compatibility testing prevents haemolytic transfusion reactions ABO System — Basics: (★) Blood Group RBC Antigen Plasma Antibody --- --- --- A A Anti-B B B Anti-A AB A and B None O None Anti-A and Anti-B Universal Donor / Recipient Rules: (★) Universal donor for RBCs: O negative (★) — no A, B, or Rh(D) antigens to trigger reaction Universal recipient for RBCs: AB positive — no antibodies against A, B, or D Universal donor for PLASMA: AB (opposite logic) — plasma contains no anti-A/anti-B antibodies Group O is NOT suitable for plasma transfusion because O plasma contains both anti-A and anti-B antibodies (★) — would attack recipient's A/B antigens if recipient is not group O --- TOPIC 16: TRANSFUSION REACTIONS Classification by Onset and Mechanism: (★) Reaction Onset Mechanism Key Features --- --- --- --- Acute haemolytic transfusion reaction Within 30 min – 24h ABO incompatibility — recipient antibodies destroy donor RBCs Fever, chills, hypotension , back pain, haemoglobinuria, DIC risk (★) Febrile non-haemolytic reaction During/shortly after transfusion Cytokines from donor leucocytes Fever, chills — NO hypotension/haemolysis Allergic reaction During transfusion IgE-mediated to donor plasma proteins Urticaria, itching ± mild fever TRALI Within 6 hours Donor anti-leucocyte antibodies react with recipient WBCs → pulmonary capillary damage Hypotension + respiratory distress (non-cardiogenic pulmonary oedema) (★) TACO During/after transfusion Volume overload Dyspnoea, hypertension (not hypotension), signs of fluid overload Delayed haemolytic reaction Days to weeks Anamnestic antibody response to minor antigens Mild jaundice, falling Hb Iron overload Long-term (multiple transfusions) Cumulative iron deposition Organ damage (liver, heart, endocrine) Distinguishing the two "look-alike" reactions: (★) Fever + chills + hypotension within 30 min = acute haemolytic transfusion reaction (ABO mismatch) Fever + chills WITHOUT hypotension/haemolysis = febrile non-haemolytic reaction (most common reaction overall) Hypotension + respiratory distress , donor antibodies against recipient leucocytes = TRALI (★) --- TOPIC 17: BLOOD COMPONENTS, PRODUCTS & SAFETY MEASURES Major Blood Components and Their Indications: (★ — core long-answer topic) Component Contains Key Indications --- --- --- Packed Red Blood Cells (PRBC) RBCs, minimal plasma Symptomatic anaemia, acute blood loss Fresh Frozen Plasma (FFP) All clotting factors Coagulopathy with active bleeding, liver failure with bleeding (★), warfarin reversal, DIC Platelet concentrate Platelets Thrombocytopenia with active bleeding (★), prophylaxis pre-procedure if very low count Cryoprecipitate Fibrinogen, Factor VIII, vWF, Factor XIII Hypofibrinogenaemia, DIC, von Willebrand disease (if specific concentrate unavailable) Albumin Plasma protein Volume expansion, hypoalbuminaemia, large-volume paracentesis Granulocyte concentrate Neutrophils Severe neutropenia with infection unresponsive to antibiotics (rare) Storage of PRBCs: (★) Citrate-Phosphate-Dextrose-Adenine-1 (CPDA-1) anticoagulant-preservative Standard shelf life: 35 days (★) at 2–6°C Safety Measures in Transfusion: (★) Measure Purpose --- --- Irradiation of blood products Prevents transfusion-associated graft-versus-host disease (TA-GVHD) in immunocompromised recipients (★) — inactivates donor lymphocytes Leucodepletion (leucoreduction) Reduces febrile non-haemolytic reactions, CMV transmission, HLA alloimmunisation Washing of RBCs Removes plasma proteins — used in IgA deficiency, severe allergic reactions ABO cross-matching Prevents ABO-incompatible haemolytic reactions (not GVHD) Pathogen reduction technology Reduces transfusion-transmitted infections Key distinction: irradiation prevents TA-GVHD ; leucodepletion prevents febrile reactions and CMV — these are commonly confused on exams (★) Infectious Screening of Donated Blood: (★) Mandatory screens universally include: HIV, Hepatitis B, Hepatitis C, syphilis (★) Hepatitis B is the most classically cited and highest-yield answer for "most commonly screened infection" in donated blood (★) Other infections (malaria, HTLV) screened regionally based on endemicity --- TOPIC 18: CLINICAL SCENARIO INTEGRATION (SAQ-STYLE REASONING) This section consolidates the clinical-reasoning patterns the SAQs test — useful as a "thinking template" for similarly-framed questions. A. Splenomegaly + Very High WCC + Neutrophilia + Left Shift + Basophilia → CML (★) Work-up: FBC/PBF → bone marrow aspirate + trephine with cytogenetics → BCR-ABL by RT-PCR or FISH → karyotyping for t(9;22) B. Heavy Menstrual Bleeding + Fatigue + Pallor + Pica → Iron deficiency anaemia (★) Clinical signs: koilonychia, angular cheilitis, glossitis Lab tests: FBC (↓Hb, ↓MCV), serum ferritin (↓), serum iron/TIBC, peripheral fi