Blood Transfusion

Question 1

Where is obtained from?

Answer 1

Has to be human blood and is a scarce resource as we can obtain only 1 pint every 4 months so must be used carefully

Question 2

What is the shelf life of blood?

Answer 2

5 weeks

Question 3

When do we use blood transfusions?

Answer 3

When there is no safer alternative available – i.e. massive bleeding or anaemic.

Question 4

What are ABO blood groups?

Answer 4

They have a base called H antigen. Group B has an extra sugar and so does A. Group O has no extra sugar just the fucose stem.

Question 5

What do Group A and B have attached to them?

Answer 5

A – N-acetyl galactosamine

B – Galactose

*the genes code for enzymes that attach the sugars

Question 6

Describe the inheritance patterns of ABO blood groups

Answer 6

A and B genes are co-dominant but O is recessive.

Question 7

What is the universal donor and universal reciever?

Answer 7

OO- is the universal donor

AB+ is the universal receiver

Question 8

Why is giving someone the wrong blood dangerous?

Answer 8

• A person has antibodies against any antigen NOT present on their own red cells e.g. a patient with group A will have antibodies against group B blood
• The antibody that reacts against miss-matched blood is IgM which is a “complete” antibody and so when it reacts it causes a full complement cascade and haemolysis of red cells and can be fatal
• IgM also cause agglutination of the red cells
• Can result in organ failure

Question 9

How is a person’s blood tested for group?

Answer 9

• 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

Question 10

What are RhD blood groups?

Answer 10

Can be RhD±, with + having D-antigen on the RBC and – having no D-antigen on the RBC

Question 11

Is the Rhd gene dominant/recessive?

Answer 11

Dominant so:
dd = no D-antigen
Dd or DD = D-antigen present

Question 12

What % of people are RhD positive and negative?

Answer 12

85% of people are RhD+, 15% are RhD-

Question 13

How are blood groups expressed?

Answer 13

ABO (ABO blood group) ± (RhD status) – e.g. AB+

Question 14

What is anti-D?

Answer 14

People who are RhD- can make anti D antibodies after exposure to RhD antigen – by transfusion of RhD+ blood or in women, if they are pregnant with an RhD+ child.

Anti-D antibodies are IgG antibodies – not as bad as IgM.

Question 15

What happens if you are exposed to D positive blood once you have anti-D?

Answer 15

The anti-D antibodies will interact with the D positive antigens on the blood cells. This won’t cause death because they are IgG and don’t go through the complement cascade. Slower, extravascular haemolysis occurs. It harms the patients as they get jaundice due to free Hb from cell lysis -> damages renal tubules and can cause kidney failure.

Question 16

What is haemolytic disease of the newborn?

Answer 16

RhD- mother has anti-D antibodies made post transfusion 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.

Question 17

Which blood group is used in an emergency?

Answer 17

O- blood

Question 18

What is important to ensure in terms of RhD during blood transfusions?

Answer 18

Transfuse blood of the same RhD group as the patient (can give RhD- to any patient). This is to ensaure patients don’t make anti-D antibodies.

Question 19

What is hydrops fetalis?

Answer 19

Life threatening oedema in the fetus. If RhD problem occurs then the baby may make it to birth but anaemia may still cause issues. The bilirubin has to be broken down by the baby’s liver too and the liver won’t cope so the BR crosses the BB barrier and causes brain damage -> death

Question 20

What are some other red cell groups?

What must be ensured following transfusion with an opposite AB?

Answer 20

• 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
• Blood is tested pre-transfusion to see if you have these antibodies – “Antibody screen”

Question 21

Why are blood components transfused?

Answer 21

To stop waste, that certain components degenerate quickly if stored as whole blood and to not fluid overload patients.

Question 22

How are blood components separated - what is in each layer?

Answer 22

Centrifuge the blood to form RBCs at the bottom, platelets middle and plasma at the top.

Question 23

How are red cells stored and given?

Answer 23

• Stores for 5 weeks at 4C
• Given via blood giving set which removes debris
• Not normally given frozen (only for rare groups) as poor recovery upon thawing

Question 24

How is fresh frozen plasma stored and is it cross matched?

Answer 24

• Store for 2 years at -30C to preserve coagulation factors
• Thaw 20-30mins before
• Dose depends on person’s weight normally 3 units needed
• No x-matching needed but need blood group as may have antigens in blood
• Won’t kill person but may cause some haemolysis

Question 25

How is blood collected?

Answer 25

Collected in a bag containing anticoagulant

Question 26

When is FFP given?

Answer 26

- Bleeding and abnormal coagulation test results (PT and APTT) - Reversal of warfarin (anticoagulant) for urgent surgery

Question 27

What is cryoprecipitate?

Answer 27

- If you thaw FFP slowly (thawed at 4-8oC overnight), some residue remains - There is precipitate at the bottom, and liquid on top – the precipitate is cryoprecipitate - The cryoprecipitate contains fibrinogen and factor VIII

Question 28

How is cryoprecipitate stored and what is the dose?

Answer 28

- Same as FFP: store at -30oC for 2 years | - Standard dose = from 10 donors (5 in a pack)

Question 29

When is cryoprecipitate used?

Answer 29

- Used in massive bleeding events, where fibrinogen is very low - Can be used for people who have very low fibrinogen for other reasons - Can be used in a rare condition: hypofibrinogenaemia (hereditary disorder of fibrinogen)

Question 30

What is the adult standard dose of platelets?

Answer 30

1 pool from 4 donors (= standard adult dose) or from 1 donor by apheresis (cell separator machine)

Question 31

How are platelets stored, shelf life and is blood group needed?

Answer 31

- Store at 22oC (Room temp) - Shelf life 5 days only (risk of bacterial infection) - Need to know blood group as platelets have low levels of ABO so otherwise would be destroyed. Also can causes RhS sensitisation as some RBC contamination

Question 32

When are platelets given?

Answer 32

- Bone marrow failure - Massive bleeding (or DIC) - Surgery (patient has low platelets) or cardiac bypass (patient on anti-platelet drugs)

Question 33

What are fractionated products?

Answer 33

The fractioned products are taken from a large pool (1000s) of donors and mixed and then fractioned off. - Factor 8 and 9 - Immunoglobulins - Albumin

Question 34

How are factor 8/9 treated and when are they used?

Answer 34

- For haemophilia A & B and F8 for vWD - Heat treated to inactivate viruses - Recombinant factor 8 or 9 alternatives are increasingly used but are expensive

Question 35

When are immunoglobulins used?

Answer 35

To treat specific illnesses. IM-Ig Specific – tetanus, anti-D and rabies IM-Ig Normal globulin – broad mix of antibodies from the population (e.g. Hep A) IV-Ig – Pre-op patients with ITP or AIHA (Autoimmune haemolytic anaemia)

Question 36

When is albumin used?

Answer 36

4.5% - for burns (where there is loss of fluid), plasma exchanges, etc. 20% - severe liver and kidney conditions (kidney tubules become porous -> proteins excreted -> poor oncotic pressure)

Question 37

How are patients protected from dangerous blood?

Answer 37

- Blood is kept safe for the patient by testing for infections and by exclusion of donors by a questionnaire (check for risky behaviour) – this isn’t fail safe though - Donors excluded if they are risky e.g. have heart problems

Question 38

What is all blood tested for?

Answer 38

- Hepatitis B and C - HIV - HTLV – Human T-Lymphotropic Virus - Syphilis - CMV or HEV

Question 39

What is the window period?

Answer 39

"Window period” of infections when the levels are too low to detect in the system and therefore tests will not detect them – therefore you cannot only rely on testing.

Question 40

How is the window period dealt with?

Answer 40

Exclude high-risk donors and use voluntary, unpaid donors

Question 41

What is prion disease (or transmissible spongiform encephalopathies) - vCJD?

Answer 41

- The abnormal folding of the prion proteins leads to brain damage - Can be transmitted by blood transfusion

Question 42

What precautions are taken to avoid vCJD?

Answer 42

All plasma pooled to make fractioned products is obtained from the USA and all blood components have white cells filtered out (white cells are essential for uptake of vCJD prion into brain).