T3 L8: Principles of Blood Transfusion

• Approximately how much blood is taken off from donor and by what technique?

  Approximately 300ml blood

  gravity venesection
• Who is Karl Landsteiner?

  Austrian-born American physician

  Recognised the problem of blood incompatibility

  Identified agglutinins in the blood

  Distinguished main blood groups

  Father of transfusion medicine: Nobel prize - 1930
• What are the significance of blood groups?

  Red cells have antigens on their surface

  Human plasma may contain antibodies to these antigens

  These can cause reactions - sometimes fatal

  This is the fundamental problem in blood transfusion
• What are agglutinins?

  Naturally occurring (pentameric) IgM antibodies
• What does transfusion of ABO incompatible blood cause?

  intravascular lysis of red cells

  This can lead to a major life-threatening transfusion reaction causing:

  • shock, hypotension, tachycardia
  • renal failure, loin pain, haemoglobinuria
  • disseminated intravascular coagulation
  • death
• Why do we have ABO antibodies?

  Antibodies to ABO antigens occur naturally due to cross reactivity with gut bacterial antigens

  These are IgM (pentameric) antibodies able to fix complement and cause red cell lysis
• What antigens and antibodies do people with blood group A have?

  Antigen on RBC surface: A

  Antibody in plasma: Anti-B

  
• What antigens and antibodies do people with blood group B have?


  Antigen on RBC surface: B

  Antibody in plasma: Anti-A

  
• What antigens and antibodies do people with blood group AB have?


  Antigen on RBC surface: A and B

  Antibody in plasma: none

  
• What antigens and antibodies do people with blood group O have?


  Antigen on RBC surface: none

  Antibody in plasma: Anti-A & Anti-B

  
• What is the Forward grouping reaction?

  Washed red cells from the patient are mixed with anti-A or anti-B antibody

  Eg this is blood group A

  
• What is the reverse grouping reaction?

  patient serum is mixed with known red blood cells to detect antibodies
• How does cross-matching work?

  1. Forward grouping (detects antigen)
  2. Reverse grouping (detects antibody)

  
• How does blood grouping with gel cards work?

  POSITIVE RESULT: if blood is at top of column (agglutination reaction)

  test for antigens: patients RBCs +:

  • anti-A antibody
  • Anti-B antibody
  • anti-D antibody (Rhesus - gives + / -)

  control: patient RBCs + patient plasma

  test for antibodies: patient Plasma +:

  • A RBCs
  • B RBCs

  Plasma + B RBCs

  
• What blood group is protective for COVID 19?

  O
• What blood group is at higher risk for COVID 19?

  A
• What is 'group and screen'?

  1. Test the ABO group of the red cells
  2. Screen the plasma for “atypical antibodies"
• What are atypical antibodies?

  arise due to sensitisation with foreign red cell antigens caused either by:

  • previous blood transfusion or
  • by pregnancy

  Atypical antibodies can cause blood transfusion reactions if the patient is transfused with incompatible blood in the future
• What is the Coombs test?

  also known as the anti-globulin test

  anti-immunoglobulin antibody to agglutinate red cells

  two types:

  • direct (DAT): whether red cells are coated with antibody
  • indirect (IAT): whether a patient is positive for Rhesus and other blood groups
• When is DAT (direct anti-globulin test) positive?

  • after a transfusion reaction and in HDN (haemolytic diseaes of newborn) (allo-antibodies)
  • in autoimmune haemolytic anaemia (auto-antibodies)
• What is the Rhesus system?

  Test for Rh antigen

  Rh positive people cannot develop anti-D antibodies
• What is Rhesus sensitisation?

  Rh -ve people can develop antibodies if they are transfused with Rh +ve blood or are pregnant with a Rh +ve baby

  the antibody generated is IgG type
• What is haemolytic disease of the newborn (HDN)?

  If an Rh -ive mother is pregnant with an Rh +ve fetus, she may produce antibodies that can cross the placenta and harm the baby

  can cause anaemia, jaundice and kernicterus (braindamage)

  
• How is HDN prevented?

  • Pregnant women have the ABO and Rh blood groups checked at 12 weeks’ booking
  • Rh -ve women (15%) receive anti-D antibody i.m. injection at 28 weeks’ gestation to prevent sensitisation
  • Baby tested at birth and if Rh +ve then the mother receives further anti-D until Kleihauer test for fetal cells in the maternal circulation becomes negative
  • If previously sensitised, then subsequent pregnancies require monitoring via trans-cranial Doppler scan and may require intra-uterine transfusions if signs of anaemia are severe
• What is in a bag of donated blood?

  Red cells

  Buffy coat:

  • white cells
  • platelets

  Plasma:

  • albumin
  • gamma globulins
  • coagulation factors

  Water, electrolytes, additives
• What is Apheresis?

  separates donated blood components

  Platelets are pooled from 4 donors to produce single unit

  Apheresis can produce a single unit from one donor
• When to give a blood transfusion?

  Severe acute blood loss:

  • Severe trauma e.g., road traffic accident
  • Massive GI blood loss
  • Obstetric blood loss

  Elective surgery associated with significant blood loss

  Medical transfusions:

  • Cancer, chemotherapy, renal failure

  Anaemia:

  • Only for symptomatic anaemia or if refractory to haematinic replacement
  • Bone marrow failure e.g., myelodysplasia or aplastic anaemia
  • Haemoglobinopathy - thalassaemia major and sickle cell disease
• What type of transfusion?

  • Blood components: Red cells, Platelets, Fresh frozen plasma, Cryoprecipitate (fibrinogen)
  • Plasma derivatives (pooled products): Immunoglobulin, Coagulation factors (e.g., Octaplex), Albumin, Convalescent antisera
  • Cell salvage (rarely done during operations)
  • Autologous transfusion (very rarely done)
• What does pre-transfusion testing include?

  • Informed consent
  • Record reason for transfusion in notes
  • Ask patient their name and check ID on wristband
  • ID (surname, name, DOB, hospital number)
  • Signature of phlebotomist (audit trail) and date
  • Do NOT use addressograph labels
  • NEVER pre-label a sample
  • Make sure the patient gets the “Right blood at the Right time”
  • Most errors are caused by failure to follow procedures
• How does blood availability in hospital work and how long do different types take?

  • O Negative (“emergency blood”): Immediate - 5 mins. Follow the hospital major haemorrhage protocol
  • Group Compatible (i.e. same group as patient)- 10-15 minutes
  • “Fully screened and cross-matched”- Approximately 45 minutes (but longer if antibodies found)
• What are the possible reaction-related complications of blood transfusion?

  • Major ABO incompatibilities: Acute renal failure, Disseminated intravascular coagulation, Death
  • Febrile non-haemolytic reactions (most common)
  • Fluid overload (TACO = transfusion associated circulatory overload)
  • Anaphylaxis and severe allergic reactions
  • Minor allergic reactions
  • Delayed transfusion reactions
  • TRALI (transfusion related acute lung injury)
• What are some possible transfusion transmitted infections (complications)?

  • Viral infections: Hepatitis (B,C), HIV, Others; HTLV, CMV; Emerging - West Nile virus
  • Bacterial infections: Syphilis, Donor bacterial infection, Contamination (e.g., pseudomonas)
  • Malaria
  • Variant CJD
• What are some other physiological hazards related to blood transfusions?

  Fluid overload:

  • do not infuse too quickly (transfuse 1 unit over 3-4 hrs if elderly or evidence of heart failure)
  • can cause acute pulmonary oedema: treat with diuretics (frusemide) to remove fluid
  • can transfuse 1 unit over 2 hours in younger patients

  Iron overload (haemosiderosis):

  • iron deposited in tissues (liver, heart, pancreas, skin)
  • can treat by iron chelation