blood transfusion Flashcards
(32 cards)
why tranfuse blood
low levels of ‘blood’
- bleeding
- failure or production
- (excess rate destruction)
why are blood groups a thing
arise from antigens
red cell antigens are expressed on cell surface
can provoke antibodies
ABO blood groups
blood group A: A antigens on surface
blood group B: no A antigens, have B
some are AB and have mix of A and B antigens
group O - null phenotype - dont have A or B
ABO blood group antigens
ABO gene encodes glycosyltransferase that sticks a partic sugar on end of sugar chain
A and B genes code for different transferase enzymes
O gene is non-functional allele - nothing is put on (recessive gene)
what antibodies are present for each ABO blood group
if blood group A on surface red cells then have antibodies against blood group B
if blood group B have antibodies against A
if O then antibodies against A and B
if AB then no antibodies against A and B
immune tolerance
immune system can distinguish between self and non-self
in utero if immune system comes across antigens which should be there (encoded by own genome) it will delete any activity against it and induce tolerance
anti-A/B are naturally occuring
Usually only develop antibody against antigen if exposed to it later in life
ABO antigens are unusual in that they are encoded by most bacteria in bowels and so are encountered
IgM formed against them as they are sugars and not proteins (so not IgG)
who can group A receive red cells from
A
O
who can group B receive red cells from
B
O
who can group AB receive red cells frmo
A
B
AB
O
who can group O receive red cells from
O
who can group A receive plasma from
A
AB
who can group B receive plasma from
B
AB
who can group AB receive plasma frmo
AB
who can group O receive plasma from
A
B
AB
O
RhD two genes
RHD gene
RHCE gene
DD
positive for RHD gene
dd
negative for RHD gene
anti-RhD
RhD negative individuals can make anti-D if exposed to RhD+ cells e.g. infusion, pregnant
what does anti-d cause
transfusion reactions 2nd in severity to ABO but can also cause haemolytic disease of newborn
blood donors screening
medical history, prev transfusion sex age travel tested for ABO and Rh blood groups screened for HepB, C and E, HIV, syphilis
blood components: plasma
clotting factors
albumin
antibodies
blood components: buffy coat
platelets
white cells/leucocytes
indications for red cell transfusions
corrects severe acute anaemia
improve QoL in pt with otherwise incorrectable anaemia
prepare pt for surgery or speed up recovery
reverse damage caused by pts own red cells e.g. sickle cell
