Blood Transfusion Flashcards
What are sources of blood?
Human blood - there is no synthetic blood but human is not risk-free.
The donors can only give 1 pint and this can only be given a max of every 4 months.
Cannot stockpile the blood -only lasts 5 weeks.
When is blood used?
Balance risks and benefits as the supply is limiting.
Do not give for anaemia (iron and B12 deficiency ) but do give for massive bleeding (plain fluids may not be sufficient)
ABO blood groups:
All of us have a common stem - the H antigen
If you’re group A - you will have an A antigen
B= B antigen added
O= no antigen added to the H antigen stem (O is recessive)
What does the A gene code for?
Adds so N-acetyl galactosamine
What does the B gene code for?
Adds galactose
What does your blood type mean?
If you are group X you will make the antigens that you are missing.
If you are group a = b antigens
B= A antigens
O= A and B antigens
IgM - crosslinks and can easily complement to the membrane attack complex which can be fatal as it causes the haemolysis of RBC
What is the most common blood type in the Uk?
O, then A, then B and then AB
- Giving the wrong type can be fatal
How do you tell what group a person is in and how do you select which blood to give them?
Need:
Patient blood
ABO group (test with known anti-A and anti-b reagents)
Select the donor unit in the same group
Cross-match - patients serum mixed with donor’s red cells - should not react if it agglutinates then it is incompatible
What are the Rh groups?
RhD is the most important - either D positive or negative
D= codes D antigen d= codes for no antigens
dd= no D antigen = RhD negative
DD or Dd = D antigen present = RhD positive (recessive)
More common to be RhD positive
What is the significance of being RhD negative?
They can make anti-D after they are exposed to the antigen (either through transfusion or a foetus who has the D)
Anti-d are IgG antibodies.
If there is a difference the RBC will be broken down into spherocytes and then they will be removed by the spleen - this can lead to jaundice + haemolysis of RBC releases Hb which is toxic to kidney tubules - but it is not fatal.
IgG can cross the placenta - if very severe it can kill the baby or later after birth it can die due to anaemia.
THEREFORE, AVOID RHD NEG PATIENTS MAKING ANTI-D.
It is fine however to give an RhD positive person RhD negative blood as they have the anti-D.
What blood type is given in an emergency?
O negative as there are no antigens in their blood.
Other antigens on the RBC are not clinically significant and so they do not cause haemolysis.
What is the process before blood transfusion?
Take a sample of the blood
Test the group
test if you have any antibodies to the blood.
This occurs everytime you have a transfusion -regardless of how soon they have had a blood transfusion prior.
What are the blood components?
Plasma - FFP (fresh frozen plasma), cryoprecipitate (rich in factors 8 and 9), plasma for fractionation (not in the UK and this pools thousands of donors)
^THIS IS DONE FOR THE ALBUMIN AND FOR FACTOR 8,9 AND IMMUNOGLOBINS E.G. ANTI-D
Platelets
Red Cells
Now can separate these by centrifuging and give to the patient just the levels that they need.
How are red cells kept and administered?
can keep for 5 weeks at 4 degrees (minimises the chances of the bacteria infecting)
when given has a filter to remove clumps/debris.
Freeze only rare blood types
How is FFP kept and administered?
Stored at -30 degrees
Shelf life of 2 years
Must thaw aprox 20-30 mins before use (if too hot, proteins will cook) - must give an hour after it is thawed
Dose = 12-15 ml/kg = usually 3 units (based on weight)
Plasma which is from a different blood type will not kill someone but can cause some haemolysis and will make the patient more anaemic.
