Lecture 8: Blood transfusions Flashcards
What are agglutinins?
Naturally occurring pentameric IgM antibodies
Link RBCs together
What shape are ABO antibodies
IgM pentameric Abs
What is the main consequence of a transfusion with incompatible blood?
Intravascular lysis
Can lead to - shock, HT, tachycardia, renal failure, loin pain, DIC and death
Describe the ABO blood grouping system
A: A Ag, anti-B Abs
B: B Ag, anti-A Abs
AB: A and B Ags, no Abs
O: no Ags, anti-A and anti-B Abs
What is forward grouping?
Test the Ag on RBC surface
What is reverse grouping?
Test Ab in plasma
Who can AB give blood to and receive blood from?
Give to AB
Receive from AB, A, B and O
Who can A give blood to and receive blood from?
Give to A and AB
Receive from A and O
Who can B give blood to and receive blood from?
Give to B and AB
Receive from B and O
Who can O give blood to and receive blood from?
Give to AB, A, B and O
Receive from O
What are the frequencies of each blood group?
O - 46%
A - 42%
B - 9%
AB - 3%
What does coagulation at the top of a blood grouping card mean?
Positive reaction
What are atypical Abs?
Arise due to sensitisation with foreign red cell Ags caused either by previous blood transfusion or pregnancy
Can cause transfusion reaction if the patient is transfused with incompatible blood in the future
What is the direct anti-globin test (Coombes)?
Tells you if the RBCs are coated with an Ab
Positive after a transfusion reaction and in HDN
What is the indirect anti-globin test (Coombes)?
Tells you in the patient is positive for Rhesus and other blood groups
What % of people are rhesus negative?
15%
What Ab is generated during rhesus sensitisation?
IgG
Which is the most important Ag in rhesus?
RhD
What is HDN?
Caused by Rh sensitisation
If a mother, who is Rh neg is pregnant with a Rh positive foetus, she may produce Abs that can cross the placenta and harm the baby
What can result from HDN?
Anaemia, jaundice and kernicterus (brain damage)
How is HDN prevented?
Rh +ve women receive antiD Ab IM injection at 28 and 34 weeks to prevent sensitisation
If baby is Rh +ve after birth the mother receives further anti-D until foetal cells become negative
If already sensitised the foetus is monitored by transcranial doppler and may receive intra-uterine transfusions
What is in the buffy coat?
White blood cells and platelets
What is in plasma?
Albumin, gamma globulins, coagulation factors
What is the name for the process where blood is taken from one arm, a single blood component is removed and then the blood is returned to the patient via their other arm?
Apheresis
When do you give a transfusion?
Severe acute blood loss: RTA, GI blood loss, obstetric blood loss
Elective surgery associated with significant blood loss
Medical transfusions: cancer, chemotherapy, renal failure
What blood components can be given during a transfusion?
Red cells, platelets, FFP, cryoprecipitate
Plasma derivatives: pooled products - Its, coagulation factors, albumin
Autologous blood
What is the difference between FFP and cryoprecipitate?
Cryoprecipitate is enriched with fibrinogen
What reactions can occur as a result of a blood transfusion?
Major ABO incompatibilities (acute renal failure, DIC, death)
Anaphylaxis and severe allergic reaction
Minor allergic reactions
Late transfusion reactions
Fluid overload
How do you treat iron overload?
Iron chelation
How do you treat fluid overload?
Diuretics
What bacterial infections may be transmitted by transfusion?
Syphylis
Pyogenic infections
Contamination infections (pseudomonas)
What viral infections may be transmitted by transfusion?
Hepatitis (B and C)
HIV
CML
