Theme 2: Lecture 8 - Principles of blood transfusion Flashcards
What is the fundamental problem with blood transfusion
- Red cells have antigens on their surface
- Human plasma may contain antibodies to these antigens
- These can cause reactions - sometimes fatal
Agglutinins
Naturally occurring pentameric IgM antibodies in the plasma
What does transfusion of ABO incompatible blood cause
intravascular lysis (red blood cells rupture)
What can intravascular lysis due to transfusion of incompatible blood cause
- shock, hypotension, tachycardia
- renal failure, loin pain, haemoglobinuria
- disseminated intravascular coagulation
- death
haemoglobinuria
presence of excess haemoglobin in the blood
Blood group A
If you belong to the blood group A, you have A antigens on the surface of your red blood cells and B antibodies in your blood plasma.
Blood group B
If you belong to the blood group B, you have B antigens on the surface of your red blood cells and A antibodies in your blood plasma
Blood group AB
If you belong to the blood group AB, you have both A and B antigens on the surface of your red blood cells and no A or B antibodies at all in your blood plasma.
Blood group O
If you belong to the blood group 0 (null), you have neither A or B antigens on the surface of your red blood cells but you have both A and B antibodies in your blood plasma.
What is cross matching by forward grouping
Determining what antigens are present on the RBCs by mixing a patient’s RBCs with known anti serum
What is cross matching by reverse grouping
Determines what antibodies are present by mixing patient’s plasma with known RBCs
Who can blood group AB give blood to
Blood group AB
Who can blood group AB receive blood from
AB, A, B, O
Who can blood group A give blood to
A and AB
Who can blood group A receive blood from
A and O
Who can blood group B give blood to
B and AB
Who can blood group B receive blood from
B and O
Who can blood group O give blood to
AB, A, B, O
Who can blood group O receive blood from
O
% of people with blood group O in the UK
46%
% of people with blood group A in the UK
42%
% of people with blood group B in the UK
9%
% of people with blood group AB in the UK
3%
What does the lad do when you send a blood sample
- Test the ABO group of red cells
- Screen for atypical antibodies
What are atypical antibodies
- These arise due to sensitisation with foreign red cell antigens
- Atypical antibodies can cause blood transfusion reactions if the patient is transfused with incompatible blood in the future
What causes atypical antibodies
- previous blood transfusion
- pregnancy
Anti-globulin or Coombs test
It uses anti-immunoglobulin antibody to agglutinate red cells
What are the two types of anti globulin or Coombs test
- Direct antiglobulin test (DAT)
- Indirect antiglobulin test (IAT)
What does the DAT tell us
The DAT tells us if red cells are coated with antibody
When is the DAT positive
- It is positive after a transfusion reaction and in HDN
- It is also positive in autoimmune haemolytic anaemia
IAT
- The IAT is used in the lab for testing blood group antigens
- It can tell us if a patient is positive for Rhesus and other blood groups
Can Rhesus positive people develop antibodies
No
When can Rhesus negative people develop antibodies
- they are transfused with Rh pos blood
- pregnant with a Rh pos baby
What antibody is generated in Rhesus sensitisation
IgG type antibodies
What is Rhesus sensitisation
When Rhesus negative people develop antibodies
Haemolytic disease of the newborn (HDN)
If a mother, who is Rh neg is pregnant with an Rh pos fetus, she may produce antibodies that can cross the placenta and harm the baby
Can a Rh negative person who develops Rh antibodies be given Rh positive blood
No
Which antigens does the Rhesus system comprise of
C, D and E (only need to know D)
What can HDN cause in the baby
- Anaemia
- Jaundice
- Kernicterus
Kernicterus
brain damage due to high levels of bilirubin in the blood
How is HDN prevented
- Rh-ve women (15%) receive anti-D antibody i.m. injection at 28 and 34 weeks to prevent sensitisation
- Baby tested at birth and if Rh+ve, mother receives further anti-D until Kleihauer test (foetal cells) becomes negative
- If already sensitised, then the foetus requires monitoring via trans-cranial Doppler scan and may require intra-uterine transfusions if signs of anaemia
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 the process that blood goes through to be separated into its different parts
Fractionation
Apheresis
A medical procedure that involves removing whole blood from a donor or patient and separating the blood into individual components so that one particular component can be removed. The remaining blood components then are re-introduced back into the bloodstream of the patient or donor.
When do you give a blood transfusion
- Severe acute blood loss
- Elective surgery associated with significant blood loss
- Medical transfusions (cancer, chemotherapy, renal failure)
- Anaemia
When do you give a blood transfusion in 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
Cryoprecipitate
plasma but enriched with fibrinogen
What type of transfusion is cell salvage
blood lost during operation is reinfused into the patient (rarely done)
What is an autologous transfusion
store blood from somebody to be given back to them at a later date (very rarely done)
What other transfusion reactions are there (excluding transfusion of ABO incompatible blood)
- Febrile non-haemolytic reactions
- Fluid overload
- Anaphylaxis and severe allergic reactions
- Minor allergic reactions
- Delayed transfusion reactions
- TRALI (transfusion related acute lung injury
What are the broad transfusion transmitted infections that you could get
- Bacterial infections
- Viral infections
- Malaria
- vCJD
What are the bacterial infections you could get from blood transfusions
- syphilis
- pyogenic infections
- contamination infections (pseudomonas)
What are the viral infections you could get from blood transfusions
- hepatitis (B,C)
- HIV
- Others - HTLV (Human T-lymphotropic virus), CMV
- Emerging - West Nile virus
Haemosiderosis
iron overload
How is iron overload treated
by iron chelation
What can happen if you transfuse too quickly
fluid overload
What can fluid overload cause
acute pulmonary oedema
Frusemide
A diuretic drug
How is fluid overload treated
with diuretics to remove fluid