principles of blood transfusions Flashcards
(43 cards)
who had the first transfusion
Pope Innocent VIII (1492) was transfused the blood of 3 boys on his deathbed
who did a dog to dog transfusion
Richard Lower 1665
what were other attempts at blood transfusion
Jean-Baptiste 1667 (sheep to human, patent died so practice abandoned for 150 years)
James Blundell 1818 did a human to human transfusion, successful treatment of postpartum haemorrhage
who is Karl Landsteiner
recognised issue of blood incompatibility
identified agglutinins in blood, distinguished main blood groups
father of transfusion medicine
what are blood transfusion milestones (since WW1)
1921 First Red Cross Voluntary Donation 1939-45 Voluntary donations 1937 First UK Blood Bank 1975 Plastic blood bags replace glass 1986 HIV testing 1991 Hepatitis C testing
what are blood groups
Red cells have antigens on surface
plasma may contain antibodies to these antigens
can cause reactions - sometimes fatal
fundamental problem in blood transfusion
what is the ABO system
A antigen B antigen AB antigen No antigen A, B, AB, O type
what are agglutinins
Naturally occurring (pentameric) IgM antibodies
what are ABO antibodies
Antibodies to ABO antigens occur naturally due to cross reactivity with gut bacterial antigens
These are IgM (pentameric) antibodies able to fix complement and cause red cell lysis
eg A antigen has anti-B
what are ABO antibodies
Antibodies to ABO antigens occur naturally due to cross reactivity with gut bacterial antigens
These are IgM (pentameric) antibodies able to fix complement and cause red cell lysis
where are blood antigens and antibodies found
Blood group A, A antigens on surface of RBCs and B antibodies in Blood plasma
Group B opposite
AB - both surface antigens and no ABs in plasma
Group O- no surface antigens but both antibodies in blood plasma
how can blood group be found
agglutination reactions
antigen present in specimen will bind to antibody and form visible aggregates
what is blood cross matching
forward (antibodies against blood group) and reverse (A/B/O cells against blood type) to see agglutination reaction
eg A forward - react with Anti-B and reverse - A and O cell reactions
anti D reaction - negative
what are the ABO compatibilities
AB - give to AB and receive AB, A, B, O
A - give to A, AB and receive A and O
B opposite of A
O - give to AB, A, B, O and receIve O
What are blood group frequencies
O 46% genotype OO
A 42% AA/AO
B 9% BB/BO
AB 3% AB
How is blood grouping done with gel cards
blood at top of the column = agglutination reaction blood at bottom = no reaction the control should be negative Cells vs Anti-A, B and D Anti D (+ve or -ve type) Control cells vs plasma Plasma vs gp A cells and gp B cells
what does a lab do when sent a blood sample
1) Test the ABO group of the red cells
2) Screen the plasma for “atypical antibodies”
what are a typical antibodies
arise due to sensitisation with foreign red cell antigens caused either by previous blood transfusion or by pregnancy
Atypical antibodies can cause blood transfusion reactions if the patient is transfused with incompatible blood in the future
what is the Coombs test
anti-globulin test
It uses anti-immunoglobulin antibody to agglutinate red cells
There are two types: direct (DAT) and indirect (IAT)
what is the DAT and IAT
The DAT =red cells coated with antibody
It is positive after a transfusion reaction and in HDN
It is also positive in autoimmune haemolytic anaemia
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
what is the Rhesus system
Rh positive people cannot develop antibodies
But 15% of people are Rh negative
what is rhesus sensitisation
Rh neg people can develop antibodies if they are transfused with Rh pos blood or are pregnant with a Rh pos baby
antibody generated is IgG type
most important antigen is RhD
What are the issues of RhD sensitisation
those who develop antibodies cannot be given +ve blood
if Rh neg mother has Rh pos baby then antibodies may harm baby
haemolytic disease of the newborn
Anaemia, jaundice and kernicterus (brain damage)
How can HDN be prevented
ABO and Rh blood group check at 12 weeks
Rh-ve get Anti-D antibody injection at 28 and 34 weeks
if already sensitised then monitor via trans-cranial doppler scan and intra-uterine transitions if sings of anaemia
