Blood Transfusion Flashcards
What are the blood groups?
What differentiates them?
ABO
Groups A and B have an extra sugar residue attached.
- “A” gene codes for – N-acetyl galactosamine.
- “B” gene codes for – Galactose.
- Group O has no extra sugar, just the fucose stem.
- ‘A’ and ‘B’ genes are co-dominant but O is recessive.
- E.G. Blood group A = AA or OA genes.
- OO- is the universal donor.
- AB+ is the universal receiver.
Which antibody reacts against miss-matched blood?
IgM
* “complete”antibody so when it reacts it causes a full complement cascade
**IgM also casues agglutinaton of the red cells
How are blood groups tested?
- A patient’s blood is tested by reacting it with known anti-A and anti-B reagents to test group
- A donor of the same group is then selected and the blood is cross-matched to be sure – check for agglutination
What are the Rh blood groups?
Can be RhD±, with (+) having D-antigen on the RBC and (-) having no D-antigen on the RBC
- The RhD gene is co-dominant
- E.G. dd = no D-antigen, Dd or DD = D+ antigen present
85% of people are RhD+, 15% are RhD-
Blood groups are usually shortened therefore to ABO (ABO blood group) ± (RhD status) – e.g. AB+.
**People who are RhD- can make D-antibodies AFTER exposure to RhD antigen – by transfusion of RhD+ blood or in women, if they are pregnant with an RhD+ child.
What are anti-D antibodies?
IgG - not as bad as IgM
What are the implications of anti-D antibodies??
Future transfusions:
- After receiving a RhD+ transfusion (and if patient is RhD-), the patient must have RhD- blood otherwise the anti-D antibodies they have made from the first transfusion would react - causes – delayed haemolytic transfusion reaction
HDN (Haemolytic Disease of the New-born):
- RhD- mother has anti-D antibodies and then if in her next pregnancy, has a child that is RhD+, the mothers IgG antibodies will cross the placenta and attack the child’s RBCs
Avoidance:
- Transfuse blood of the same RhD group as the patient (can give RhD- to any patient).
- O- blood is used in an emergency as it cannot react with any combination in the patient (no antigens)
What are other blood groups?
There are other antigens on RBCs that we do not routinely match – e.g. RhC, c, E, e, and others; Kell, Duffy, Kidd
About 8% of patients transfused form antibodies to these antigens
So once the patient has formed these Ab, you must use the antigen- blood or risk a delayed haemolytic reaction
They can test your blood pre-transfusion to see if you have these antibodies – “Antibody screen”
Why do we give patients components of blood?
to stop waste - certain components degenerate quickly if stored as whole blood and to not fluid overload patients
- Centrifuge the blood to form RBCs at the bottom, platelets middle and plasma at the top
What are the features of red cells?
- Stores for 5 weeks at 4C
- Given via blood giving set – removes debris
- Not normally given frozen (only for rare groups) as poor recovery upon thawing
What are the features of fresh frozen plasma?
- Store for 2 years at -30C – thaw 20-30mins before
- No x-matching needed but need blood group
When do you give FFP?
Bleeding and abnormal coagulation test results (PT and APTT) - monitor response clinically and by coagulation test
Reversal of warfarin (anticoagulant) for urgent surgery
What is cryoprecipitate?
Cryoprecipitate – 1 dose from 10 donors, formed from frozen plasma thaw residue
Contains fibrinogen and F8 – so given for massive bleeding and hypofibrinogenaemia
Stored at -30C for 2 years
What are the features of platelets?
1 pool from 4 donors or from 1 donor by apheresis
Stored at 22C (but constantly agitated) for 5 days only
Platelets have low levels of ABO antigens on so wrong ones destroyed quickly but can cause RhD sensitisation as some RBC contamination
When would you use platelets?
bone marrow failure, massive bleeding (or DIC), surgery (patient has low platelets) or cardiac bypass (patient on anti-platelet drugs)
Platelets are often overused
What are fractionated products?
The fractioned products are taken from a large pool (1000s) of donors and mixed and then fractioned off
Products:
- Factor 8 and 9 – for haemophilia A & B and F8 for vWD
> Heat treated to inactivate viruses
> Recombinant factor 8 or 9 alternatives are increasingly used by are expensive
- Immunoglobulins – to treat specific illnesses.
> IM-Ig – Specific – tetanus, anti-D and rabies
> IM-Ig – Normal globulin – broad mix in population (e.g. HAV).
> IV-Ig – Pre-op patients with ITP or AIHA (Autoimmune haemolytic anaemia) - Albumin:
> 4.5% - for burns, plasma exchanges, etc.
> 20% - severe liver and kidney conditions
