10. Blood transfusion and blood groups

1. Definition

• Blood transfusion → transfer of blood or blood components from a donor to a recipient
• Modern practice → component therapy, not whole blood
• Autologous transfusion → patient's own blood (predeposit, cell salvage)

2. Blood group doctrine

ABO system

• Discovered by Landsteiner (1901)
• Antigens (A, B) on red cells; antibodies (anti-A, anti-B, IgM) in plasma
• Antibodies are naturally occurring → present without prior exposure
• Groups:
  • O → no antigens; anti-A and anti-B; universal red cell donor
  • A → A antigen; anti-B
  • B → B antigen; anti-A
  • AB → A and B antigens; no antibodies; universal plasma donor, universal red cell recipient
• Plasma compatibility is the reverse of red cell compatibility

Rhesus (Rh) system

• Main antigen → D
• Rh positive → 85% of people
• No natural anti-D → formed after exposure (transfusion, pregnancy)
• Rh-negative woman with Rh-positive fetus → haemolytic disease of the newborn; prevented by anti-D immunoglobulin

Other systems

• Kell, Duffy, Kidd, MNS → irregular antibodies after previous transfusion or pregnancy

3. Indications

• Acute blood loss → class III–IV haemorrhage
• Anaemia → restrictive threshold:
  • Haemoglobin < 70 g/L in most patients
  • < 80 g/L with cardiovascular disease
• Massive transfusion → trauma, obstetric, surgical bleeding
• Components:
  • Red cells → anaemia, blood loss
  • Platelets → thrombocytopenia with bleeding or before surgery
  • Fresh frozen plasma (FFP) → coagulation factor deficiency
  • Cryoprecipitate → fibrinogen < 1.5 g/L

4. Compatibility tests

1. ABO and Rh grouping of recipient and donor
   • Forward grouping → patient's red cells with anti-A, anti-B, anti-D reagents
   • Reverse grouping → patient's plasma with known A and B cells
2. Antibody screen → irregular antibodies in recipient plasma
3. Crossmatch → recipient serum with donor red cells
   • Saline (immediate spin) at room temperature → ABO incompatibility
   • Indirect antiglobulin (Coombs) test at 37 °C → IgG antibodies
   • Electronic crossmatch → when grouping and screen are valid
4. Bedside ABO check → recipient's blood with anti-A and anti-B at the bedside
5. Biological test → 3 × 10–20 mL given with 3-minute pauses, watching for reaction (traditional in Eastern European practice)
6. Emergency without time for crossmatch → O negative red cells (O positive in men and older women)

5. Rules and technique of transfusion

• Written consent where possible
• Pre-transfusion sample → labelled at the bedside
• Positive patient identification at every step → name, date of birth, hospital number
• Check the bag:
  • Group and number match the compatibility label
  • Expiry date
  • Integrity, no clots or discolouration
• Giving set with a 170–200 µm filter
• Red cells → start within 30 min of leaving storage, complete within 4 h
• Platelets → stored at 22 °C; do not refrigerate
• No drugs or solutions other than 0.9% saline in the same line
• Observations → before start, at 15 min, at the end
• Watch the patient closely in the first 15 min
• Document the transfusion

6. Complications

Acute (< 24 h)

• Acute haemolytic reaction → ABO incompatibility, mostly identification error
  • Fever, rigors, loin and chest pain, hypotension, haemoglobinuria
  • Disseminated intravascular coagulation (DIC), acute kidney injury
• Febrile non-haemolytic reaction → most common; cytokines, leucocyte antibodies
• Allergic reaction → urticaria, itch
• Anaphylaxis → IgA deficiency with anti-IgA antibodies
• Transfusion-related acute lung injury (TRALI) → non-cardiogenic pulmonary oedema within 6 h
• Transfusion-associated circulatory overload (TACO) → elderly, heart failure
• Bacterial contamination → platelets most often; septic shock
• Air embolism

Delayed (> 24 h)

• Delayed haemolytic reaction → 5–10 days, irregular antibodies (Kidd)
• Transfusion-associated graft-versus-host disease → prevented by irradiated products
• Post-transfusion purpura
• Iron overload → repeated transfusions
• Infections → hepatitis B and C, human immunodeficiency virus (HIV), syphilis, cytomegalovirus

Massive transfusion

• Definition → > 10 units of red cells in 24 h, or replacement of 1 blood volume
• Complications:
  • Hypothermia
  • Hypocalcaemia → citrate binds calcium
  • Hyperkalaemia
  • Dilutional coagulopathy, thrombocytopenia
  • Acidosis

Management of a reaction

1. Stop the transfusion immediately; keep the line open with saline
2. Check patient identity and the bag label
3. ABCDE assessment, oxygen, fluids
4. Adrenaline for anaphylaxis
5. Return the bag; send blood for direct antiglobulin test, repeat group, full blood count, clotting, urine for haemoglobin
6. Inform the blood bank