2.8 Blood Transfusion Flashcards
Blood group refers to
Combination of RBC antigens present on membrane
Blood group system is
Collection of one or more RBC antigens under the control of a single gene
Most clinically significant blood group systems
ABO and Rh
When are antibodies against RBC antigens clinically significant
When they can cause haemolysis
Haemolysis
Destruction of rbc
HTR
Haemolytic transfusion reaction
When incompatible RBC are transfused
HDFN
Haemolytic disease of the fetus and newborn
Fetus has different RBC antigens to the mother and the mother produces an antibody to that RBC antigen which crosses the placenta
Types of antibodies against RBC antigens
Naturally occurring
Acquired alloantibodies
Naturally occurring antibodies
ABO antibodies - antiA and antiB
Production stimulated when immune system encounters the missing blood group in food or mo’s at an early age
Mostly IgM antibodies
IgM antibodies
5 Y shaped units giving a pemtameric structure
Can IgM ABO antibodies cause HTR’s and HDFN’s?
Only HTR’s, can’t cross placenta for HDFN’s
How are alloantibodies acquired
Alloimmunisation - active immunisation to non-self RBC antigens following exposure from another individual eg incompatible blood transfusion or pregnancy
Rhd
What type of antibodies are acquired alloantibodies
IgG
Y shaped
Can IgG antibodies cause HTR’s and HDFN’s
Delayed HTRs and can cross placenta to call HDFN
Which antigens do group a individuals express on their RBC
A antigens
Which antigens do group o express on RBC
Neither a nor b
What can antibodies do
Activate complement
Cause potentially fatal haemolysis
How are a and b antigens formed
Adding a sugar residue onto a common glycoprotein and fucose stem
What’s the fucose stem on antigens also known as
H antigen
How does the a gene determine antigen
Codes for enzyme that adds n Acetyl galaxtosamine to the H antigen
How does the b gene determine b antigen
Codes for enzyme which adds galactose to h antigen
Red cells shelf life
35 days
Platelet shelf life
7 days
FFP shelf life
3 years
Cryoprecipitate shelf life
3 years
Dose of ffp
3 units
What does cryoprecipitate contain
Fibrinogen and factor 8
When to use cryoprecipitate
Lots of bleeding and fibrinogen is low
Platelet transfusion use
Bone marrow failure (leukaemia, decreased platelets)
Massive bleeding
Veryblow platelets and patient needs surgery
Cardiac bypass patient on anti platelet drugs
