Study 20 flashcards on Blood Transfusion Medicine Flashcards with OmpathStudy. Quick, focused revision for Kenyan medical and health students by unit and year.
Q1. List the ABO blood group system — antigens, antibodies, can donate to, can receive from
Answer: Group A → A antigen, Anti-B → donate to A, AB → receive from A, O Group B → B antigen, Anti-A → donate to B, AB → receive from B, O Group AB → A and B antigens, no antibodies → donate to AB only → Universal Recipient → receive from all Group O → no antigens, Anti-A and Anti-B → Universal Donor → receive from O only Universal RBC donor = O negative Universal plasma donor = AB positive
Q2. Explain the Rh blood group system and the pathogenesis of HDN
Answer: Most important antigen = D antigen Rh negative = no D antigen; antibodies NOT naturally present → develop only after exposure ( sensitisation ) HDN pathogenesis: 1st pregnancy → Rh-negative mother carries Rh-positive fetus → uneventful At delivery → fetal RBCs enter maternal circulation → mother forms anti-D IgG 2nd Rh-positive pregnancy → maternal anti-D IgG crosses placenta → attacks fetal RBCs → haemolysis Consequences → mild jaundice → severe anaemia → hydrops fetalis → intrauterine death Prevention → anti-D immunoglobulin (Rhogam) within 72 hours of delivery/sensitising event + at 28 weeks
Q3. List the clinically important blood group systems after ABO and Rh with key associations
Answer: Kell (3rd) → strong immunogen; causes HDN and haemolytic transfusion reactions Duffy (4th) → Duffy-null individuals resistant to Plasmodium vivax malaria Kidd (5th) → notorious for causing delayed haemolytic transfusion reactions MNS (6th) → variable clinical significance
Q4. List the 3 steps of pre-transfusion compatibility testing
Answer: Step 1 — ABO and Rh typing → determine patient's blood group and Rh status Step 2 — Antibody screen → patient's serum tested against panel of reagent RBCs to detect unexpected/irregular antibodies Step 3 — Crossmatch → patient's serum mixed directly with donor RBCs → agglutination or haemolysis = incompatible → do not transfuse Crossmatch primarily detects irregular antibodies in patient serum reacting against donor RBC antigens
Q5. Distinguish DAT from IAT — what each detects and clinical uses
Answer: DAT (Direct Antiglobulin Test) Detects antibodies already bound to patient's own RBCs in vivo Uses → haemolytic transfusion reactions, autoimmune haemolytic anaemia, HDN Positive DAT = antibodies actively coating patient's RBCs inside the body IAT (Indirect Antiglobulin Test) Detects free antibodies in patient's serum in vitro Uses → pre-transfusion antibody screening, crossmatching Crossmatch = essentially a form of IAT
Q6. What is the metabisulfite test? What does it detect and what is its limitation?
Answer: Sodium metabisulfite added to blood → creates deoxygenating environment HbS becomes insoluble → RBCs sickle → positive result confirms presence of HbS Detects both sickle cell trait (HbAS) and sickle cell disease (HbSS) Limitation → does NOT distinguish trait from disease Haemoglobin electrophoresis needed to distinguish
Q7. List the blood products, their contents, storage conditions, and indications
Answer: pRBCs → red cells, minimal plasma → 1–6°C, 35–42 days → symptomatic anaemia, haemorrhage FFP → all coagulation factors, fibrinogen, albumin, immunoglobulins; NO platelets → −18°C, 12 months → coagulopathy, liver disease, warfarin reversal, DIC, TTP Platelets → platelets in plasma → 20–24°C with agitation, 5 days → shortest shelf life; highest bacterial contamination risk Cryoprecipitate → fibrinogen, Factor VIII, Factor XIII, vWF, fibronectin; NO Factor IX, VII → −18°C, 12 months → haemophilia A, vWD, hypofibrinogenaemia, DIC Albumin → heat-treated, virus-safe → hypoalbuminaemia, burns, cirrhosis, nephrotic syndrome
Q8. Describe acute haemolytic transfusion reaction — cause, mechanism, features, management
Answer: Most serious immediate reaction Cause → ABO incompatibility; most common cause = clerical error (wrong blood, wrong patient) Mechanism → recipient preformed IgM antibodies bind donor ABO antigens → complement activation → rapid intravascular haemolysis Features → fever, rigors, back/flank pain, haemoglobinuria (red/brown urine), haemoglobinaemia, hypotension, tachycardia, DIC, acute renal failure Management: Stop transfusion immediately — most important first step Keep IV line open with normal saline Check patient identity against blood product label Send samples → repeat crossmatch, DAT, FBC, renal function, urine for Hb Monitor urine output; treat DIC and renal failure Notify blood bank
Q9. Describe febrile non-haemolytic transfusion reaction — cause, features, management, prevention
Answer: Most common transfusion reaction overall Cause → recipient antibodies react against donor leukocyte HLA antigens OR cytokines accumulate in stored blood Features → fever (≥1°C rise), chills, malaise — no haemolysis Management → slow or stop transfusion; give paracetamol Prevention → leukoreduction (filtration removes white cells before storage)
Q10. Describe allergic/urticarial reaction and anaphylactic transfusion reaction
Answer: Allergic/Urticarial: Cause → recipient IgE antibodies react against donor plasma proteins Features → urticaria, pruritus, flushing; no fever, no haemolysis Management → slow transfusion; antihistamines (chlorpheniramine) Anaphylaxis: Most commonly in IgA-deficient patients with anti-IgA antibodies Even trace IgA in donor plasma triggers severe anaphylaxis Management → stop transfusion immediately; adrenaline, corticosteroids, IV fluids Future transfusions → washed RBCs or IgA-deficient products
Q11. Distinguish TACO from TRALI — mechanism, BP, JVP, diuretics, CXR
Answer: TACO → volume overload BP → elevated JVP → raised Responds to diuretics → YES CXR → bilateral infiltrates + cardiomegaly TRALI → donor antibodies (anti-HLA/anti-neutrophil) attack recipient leukocytes in lungs → non-cardiogenic pulmonary oedema Onset within 6 hours BP → normal or low JVP → normal Responds to diuretics → NO CXR → bilateral infiltrates, normal heart size Management → supportive; high-flow O2, mechanical ventilation
Q12. Describe bacterial contamination as a transfusion reaction — which product, organisms, features, management
Answer: Most commonly affects platelet concentrates → stored at room temperature → allows bacterial growth Common organisms → Staphylococcus epidermidis, Staphylococcus aureus, gram-negative bacteria Features → high fever, rigors, severe hypotension, septic shock during or immediately after transfusion Management: Stop transfusion immediately Blood cultures from patient AND blood bag Broad-spectrum antibiotics Resuscitate
Q13. Describe delayed haemolytic transfusion reaction — timing, cause, features, management
Answer: Timing → 3–10 days after transfusion Cause → low-level alloantibodies from previous transfusion/pregnancy not detected on antibody screen → after transfusion, anamnestic (memory) immune response → antibody levels rise → attack transfused RBCs Kidd system antibodies → notorious for causing this Features → unexpected fall in Hb, mild jaundice, positive DAT Management → usually mild and self-limiting; monitor renal function
Q14. Describe post-transfusion purpura — timing, mechanism, features, management
Answer: Timing → 5–10 days after transfusion Mechanism → patient develops antibodies against platelet-specific antigen ( HPA-1a ) on donor platelets → antibodies cross-react with and destroy patient's own platelets Features → sudden severe thrombocytopenia → widespread purpura and bleeding Predominantly affects women sensitised through previous pregnancies Management → high-dose IVIG
Q15. Describe TA-GvHD — timing, mechanism, features, mortality, prevention, who needs irradiated blood
Answer: Timing → 1–6 weeks after transfusion Mechanism → viable donor T-lymphocytes engraft in immunocompromised host → attack host tissues (skin, liver, GI tract, bone marrow) Features → rash, diarrhoea, liver dysfunction, pancytopenia Mortality → exceeds 90% — no effective treatment once established Prevention → irradiation of blood products with gamma radiation (25–50 Gy) → inactivates donor T-lymphocytes Who needs irradiated blood: Immunocompromised patients Intrauterine transfusion recipients Directed donations from blood relatives HSCT recipients Hodgkin lymphoma patients
Q16. List special blood product modifications, what they prevent, and when they are used
Answer: Leukoreduced → WBCs removed by filtration → prevents FNHTR, CMV transmission, HLA alloimmunisation, platelet refractoriness → standard for most transfusions Irradiated → gamma radiation inactivates donor T-lymphocytes → prevents TA-GvHD → for immunocompromised, HSCT, intrauterine transfusions, directed donations from relatives Washed RBCs → plasma proteins, IgA, cytokines removed by saline washing → for IgA-deficient patients with anti-IgA antibodies; severe/recurrent allergic reactions CMV-negative → from CMV-seronegative donors → for CMV-seronegative immunocompromised patients, pregnant women, premature neonates; leukoreduced blood is acceptable alternative
Q17. Define massive transfusion. List its complications
Answer: Definition → replacement of 100% blood volume in 24 hours OR 10 units pRBCs in 24 hours OR 4 units pRBCs in 1 hour Complications: Hypothermia → cold stored blood lowers core temperature; worsens coagulopathy Hypocalcaemia → citrate in stored blood chelates circulating calcium Hyperkalaemia → K+ leaks from stored RBCs during storage Dilutional coagulopathy → clotting factors and platelets diluted Metabolic acidosis → stored blood has low pH
Q18. Describe the massive transfusion protocol (MTP) and additional management
Answer: Ratio → 1:1:1 (FFP : Platelets : pRBCs) → mimics whole blood, prevents dilutional coagulopathy Additional management: Tranexamic acid given early → inhibits fibrinolysis → reduces blood loss in trauma Calcium supplementation → counteracts citrate chelation Warm all blood products → prevents hypothermia Correct acidosis
Q19. How do you manage an unknown blood group in an emergency? Suspected acute haemolytic reaction?
Answer: Unknown blood group emergency: Give O negative pRBCs immediately If plasma needed → give AB positive FFP Switch to type-specific blood once blood group identified Suspected acute haemolytic reaction: Stop transfusion immediately Keep IV line open with normal saline Check patient identity against blood label Send → repeat crossmatch, DAT, FBC, renal function, urine Hb Monitor urine output; manage DIC and renal failure Notify blood bank; complete incident report
Q20. List the complications of repeated transfusions and their management
Answer: Iron overload → each unit pRBCs = ~250 mg iron; no mechanism to excrete excess → treat with desferrioxamine or deferasirox Alloimmunisation → repeated exposure to foreign RBC antigens → multiple alloantibodies → crossmatching increasingly difficult Delayed haemolytic reactions → from previously formed alloantibodies CMV infection → use leukoreduced or CMV-negative blood Hypersplenism → from chronic haemolysis and repeated transfusions