HAEM: Transfusion Flashcards
Three requirements of transfusing red cells
Make sure group is right
Screen for antibodies
Cross match
spun down
red cells/packed cells - what you usually transfuse
plasma –> spin down further
platelets –> spin down further
apheresis machine –> spins your blood, gives red cells back
collect plasma, do it more frequently than if you donate whole blood
do it every two weeks
Collect by apheresis
More time dependent
Patients need to come in on time
get blood group right
red cells express antigens (ABO/Rh)
People have antibodies for antigens, eg Anti-B antibodies.
Bad reactions can occur.
A - a antigen
B - b antigen
both or none
O group - none. Backbone, but no carbohydate on the end which makes it A/B
People with A antigens will develop anti-B antibodies
D, C, E, c, e
RhD antigen = most immunogenic
- Don’t have D antigen and body comes into contact with it –> body will make anti-D; risk is quite high.
- Antibodies formed after pregnancy or transfusion.
Pregnancy: Mother will develop anti-D antibodies (from previous pregnancy or transfusions), these will pass through the placenta and affect the D positive baby.
O > A > B > AB
Group + screen: Identify groups and antibodies
Crossmatch: test for compatible units of packed cells and blood ordered and reserved for patient
- Ideal if you have plenty of time
O negative –> universal group.
O has no antigens, person won’t develop antibodies if Rh-.
Aggregation and agglutination –> blood clumps at bottom.
reagents = anti A or anti B
Column agglutination technology - reagents + pipetted blood which is spun down. Lump at top if reaction; otherwise spun to bottom.
If a patient is transfused, how long is it valid for?
72 hours –> new antibodies might develop.
