Haem: Blood Transfusions 1 Flashcards
Describe how the consequences of rhesus incompatibility are different from ABO incompatibility in a patietn receiving a blood transfusion.
- ABO - immediated haemolytic transfusion reaction (intra vascular haemolysis can be fatal)
- Rhesus - delayed haemolytic transfusion reaction
Difference between Rh D +ve and -ve patients
There are many different blood group antigens but Rh D is the most immunogenic antigen
List some other red cell antigens that can lead to transfusion reactions.
C, c, E, C
Duffy and Kidd (particularly important for delayed transfusion reactions)
Who can recieve Rh D -ve blood
can be given to anyone - but often in short supply
so reserved for RhD
Who should never recieve Rh D +ve blood?
Rh -ve women of childbearing age
(can be given it to Rh -ve men e.g. in trauma situation –> they will become sensitised –> will need Rh-ve blood in future)
What is a dangerous consequences of rhesus incompatibility in a pregnant woman?
Haemolytic disease of the newborn
severe fetal anaemia
hydrops fetalis
How is the patient’s blood group tested?
- Anti-A, anti-B and anti-D reagents are mixed with the patient’s red blood cells
NOTE: a positive result means that the red cells will float to the top of the vial
How can the types of red blood cell antibodies in the patient’s serum be identified?
Known A and B group red blood cells are mixed with the patient’s plasma (which contains IgM antibodies)
What must be done before every transfusion?
Group and screen
Describe how the antibody screen of a patient’s plasma works.
- Conducted using the indirect antiglobulin test (IAT)
- 2 or 3 reagent red blood cells are used which contain all the important red cell antigens
- The patient’s serum is incubated with these screening cells
- Anti-human immunoglobulin is added to the solution which allows briding of red cells that are coated with IgG
- This results in the formation of a visible clump
- This is a group and screen
What labels are included on issued blood?
ABO and D type
Other Rh antigens and Kell
Which patient group should receive K negative blood?
Women of childbearing potential
What is a full crossmatch?
- Uses indirect antiglobulin test
- Patients plasma is incubated with DONOR red cells at 37 degrees for 30-40 mins
- Anti-human immunoglobulin is added to allow cross-linking of antibodies
- Formation of a clump would suggest that antibodies against donor red cell antigens are present in the patient’s plasma
only done if patient has had previous transfusion
What is an immediate spin?
- Incubate patient’s plasma and donor red cells for 5 mins and spin
- This will only detect ABO incompatibility
- Used in emergency situations
- IgM anti-A or anti-B will bind to donor RBCs, fix complement and lyse cells
What is an electronic crossmatch?
- Also called electronic issue (EI)
- Compatibility is determined by an IT system without physical testing of donor cells against plasma
NOTE: this is quick, requires fewer staff and allows better stock management
How long do red cells survive in storage?
35 days in 4 degrees
How soon after leaving storage do red cells need to be transfused?
4 hours
NOTE: red cells can be returned to the fridge within 30 mins of leaving storage
Describe how platelets are cross-matched.
They do NOT need cross-matching because the antigens are weakly expressed
Why + when do we give blood/components
don’t give blood unless definitely necessary
Which antigens are important when considering plasma transfusion?
Only ABO
If group O blood is given to A, B or AB patients, what precaution should you take?
Use high titre negative blood (i.e. plasma contains low levels of anti-A and anti-B antibodies)
What is the universal donor for:
- Red blood cells
- Plasma
- Red blood cells = O-
- Plasma = AB (contains no anti-A or anti-B antibodies)
Why do platelets have a shorter shelf-life than red blood cells?
They are stored at room temperature so they are more likely to get contaminated by bacteria
What should you do if a patient receiving a platelet transfusion develops a fever?
- Stop the platelets and take blood cultures
- Platelets should be sent back to the lab for microbiological testing
