Blood groups + transfusions Flashcards
Blood group locations
Located on surface of RBC
RBC
Lipid bilayer
Sugar residues + proteins in it
Sugar residues on RBC
Form one type of blood group system e.g. ABO
Determined by genes
Proteins on RBC
Form another type of blood group system e.g. Rhesus (Rh)
Determined by genes
Number of antigens
Over 300
Antibodies
Immunoglobins in plasma which react specifically with their antigen
Autoantibodies
React with antigens present on person’s own red cells
Alloantibodies
Produced by the person against antigens not present on person’s own red cells
- -> naturally occurring (exposure to environment)
- -> immune (contact with antigen)
Agglutination
Occurs when antigen mixed with corresponding antibody
ABO Blood groups
Defined by presence or absence of polysaccharide antigens A and B
Antibodies against antigens A and B
Naturally occurring antibodies (IgM) against these antigens in negative individuals
- -> Anti-A
- -> Anti-B
IgM
Cold-acting –> bind at room temp
Activate complement
Blood Group A
Has anti-B in plasma
–> will be agglutinated by anti-A
Blood group B
Has anti-A in plasma
–> will be agglutinated by anti-B
Blood group O
Has anti-A and anti-B in plasma
–> will not be agglutinated
Blood group AB
No ABO antibody in plasma
Will be agglutinated by anti-a and anti-b
Phenotype
Antigens detectable on red cell membrane
Genotype
Antigens encoded in DNA (1 copy from each parent)
A Phenotype
AA
AO
Genotypes
B Phenotype
BB
BO
Genotype
AB Phenotype
AB Genotype
O Phenotype
OO Genotype
Rhesus proteins
3 pairs of proteins Inherited as triplet from each parent D or d (d= no D) C or c E or e
Rhesus antibodies
Immune only
Will only be produced if person is exposed to antigen through transfusion, pregnancy or transplantation
D antigen
Most clinically important
80% People without D antigen will develop anti-D if not exposed to it
D either present or absent
D positive
No anti-D antibodies
D negative
anti-D antibodies (only produced if contact with D positive)
CcDE red cells
Agglutinate with anti-C, anti-c, anti-D and anti-E but not anti-e
cdE red cells
Agglutinate with anti-c, anti-E
Patient RhD positive
Donor can be RhD positive or negative
Patient RhD negative
Donor RhD negative
Avoid giving RhD +ve blood to RhD negative, especially women of child bearing potential
Haemolytic disease of foetus and newborn
Can occur when mother is Rh- and father Rh+
–> baby can be Rh+
First pregnancy haemolytic disease
Nothing much happens
Antibodies being sent in one direction from mother to child
During birth= blood mixed + anti-D antibodies are produced
Second pregnancy haemolytic disease
anti-D stimulated, crosses placenta and destroys foetal red cells
Haemolytic disease MOA
Rh + father
Rh- mother carrying first Rh+ foetus
Rh antigens from developing foetus can enter mother’s blood during delivery
In response to foetal Rh antigens, mother produces anti-Rh antibodies
If women becomes pregnant with another Rh+ foetus, anti-Rh antibodies will cross placenta + damage foetal red blood cells
Haemolytic disease consequences
Foetal anaemia (can be fatal) Neonatal jaundice (can cause brain damage) Kernicterus (bilirubin build up can cause neurological damage)
Haemolytic disease treatment
Prophylaxis after a sensitising event during pregnancy
–> prophylactic anti-D Ig to all negative mothers in 3rd trimester
Postnatally is baby is D-positive
Red cell transfusion
Unit with most plasma removed
Red cells in additive solution transfusion
With most plasma
White cells + platelets removed
Leukocyte-depleted red cells transfusion
99.9% of white cells removed
Reasons for transfusion
Anaemia Bone marrow failure Sickle cell disease Malaria Acute blood loss
Red cell storage temp
4 degrees
Red cell shelf life
35 days
Clinical use of red cells
Blood loss Bone marrow failure Haemolysis Inherited haemoglobin disorders Anaemia due to iron, B12 or folate deficiency- avoid transfusion, give haematinic replacement therapy
Immune complication to Transfusion
Acute haemolytic transfusion reaction
Febrile non-haemolytic
Allergic (anaphylaxis)
Post transfusion purpura
Non-immune complication to Transfusion
Fluid overload
Iron overload
AB person transfusion
Can receive A, B and O cells a contain no ABO antibody
AB person giving transfusion
Can’t be given to A, B or O
O person giving transfusion
Can be given to any blood type
Resistant to anti-a, anti-b or anti-AB
O person transfusion
O cannot receive A and B cells because contains anti-a or anti-b
Rhesus positive
Not to pregnant
But can be given to men in need of massive transfusion
Patient Group O
Can be given O, A, B or AB
Patient Group A
Can be given A or AB
Patient Group B
Can be given B or AB
Patient Group AB
Can be given AB
Organising a transfusion
Blood grouping (ABO and RhD typing) Antibody screening (detects atypical antibodies) Cross matching (mix donor red cells + patient serum)
Transfusion reaction symptoms
Restless
Flushing
Anxiety
Abdo pain
Transfusion reaction Signs
Fever
Hypotension
Haemoglobinuria
Transfusion reaction what to do
STOP TRANSFUSION
Maintain venous access with saline
Commence resuscitation
