Blood transfusions

Question 1

Describe ABO and Rh D antigens and antibodies

Answer 1

1. ABO antigens:

Group A: only have A antigen on their red blood cells
Group B: only have B antigen
Group AB: have both A and B
Group O: don’t have any ABO antigens

2. ABO antibodies:

Individuals generate ab to ags which aren’t on their rbcs (remember A + B alleles codominent and O is recessive/non functional)
Hence group A have anti B antibodies
Group B have anti A antibodies
Group AB have no ABO antibodies
Group O have anti A, B and AB antibodies
No reaction if baby has different blood group because mums IgM ab don’t cross placenta to attack babys rbc

3. D antigen

D antigen is the most immunogenic which gives the person + or - on their blood group
But this time anti D antibodies are only generated through exposure to the foreign D antigen
IgG in mum can cross plaenta to attack babys rbcs

Question 2

Alloantibodies

Answer 2

• Definition: these are antibodies which are produced following exposure to foreign rbc antigens - this occurs during preg, transfusion, transplant when donors rbc has different antigens
• This can lead to hemolysis of transfused rbcs or hemolytic disease of newborn: rhesis D + baby causes - mum to get sensitised so when has another rh+ baby IgG from mum cross placenta and damages fetal rbc causing hydrops fetalis, splenomegaly, hyperbillirubinaemia, kernicterus

Therefore if Rh- mum prophylactic anti D given routinely (28 weeks) and when a possible sensitising event has occured (abdo trauma, amniocentesis, birth). It binds to rh+ ag on fetal red cells circulating in mum and destroys them

Question 3

Group + screen vs crossmatch

Answer 3

G&S: determines ABO and RhD status and screens for any atypical antibodies. Takes 40 mins, recommended if blood loss not anticipated but blood may be required

Crossmatch: mixes patients bloods with donor to see if any immune reaction occurs so that donors blood can be issued and transfused. 40 mins also. Performed if blood loss anticipated

Question 4

Observing during transfusion

Answer 4

Obs on patient before transfusion, 15 minutes in, 1 hour in, at completion

Question 5

Donor requirements + screening

Answer 5

• 17-65 years
• 50-158 kg
• Not if cancer, heart conditions, blood diseases, organ transplant, injected non prescribed drugs, pregnant, travelled, hepb/c carrier, HIV, received any blood products after 1 jan 1980
• Checks Hb before. Also screen for blood group, ab, hepb/c/e, hiv, cmv, malaria
• Men every 12 weeks and women every 16

Question 6

Steps taking to keep transfusions safe

Answer 6

• Keep staff up to date with training
• Identification at all stages
• Handwrite label at bedside
• 2 person checks
• all done electronically via tracker now