Blood transfusion

Question 1

How much blood and how frequently can one donor give?

Answer 1

1 unit (1 pint) every 4 months

Question 2

What glycoprotein and fructose stem is common to everyone?

Answer 2

H stem

Question 3

What are A and B antigens?

Answer 3

The A and B antigens are made by the addition of a sugar residue onto the common glycoprotein and fructose stem (H stem)

Question 4

What do the A and B genes encode?

Answer 4

A = An ENZYME that adds N-acetyl galactosamine to the H stem

B = An ENZYME that adds galactose to the H stem

Question 5

Describe the inheritance pattern of the ABO blood groups.

Answer 5

A and B genes are codominant

O is ‘recessive’ because it doesn’t code for anything at all.

Question 6

Which antibodies would someone in blood group A possess? Why?

Answer 6

Anti-B antibodies because each person produces antibodies against any antigen that is NOT present on their own red cells.

Question 7

What class of immunoglobulin are these antibodies? What do they do when they come into contact with their antigen?

Answer 7

IgM They are naturally occurring (nearly from birth) and lead to complete cytokine storm/full activation of complement

They cause haemolysis via complement, This is often FATAL It can lead to cytokine storm, lysis, cardiovascular collapse and death

Question 8

In the laboratory, what would you see if you were to mix the plasma of someone of blood group A with the red cells of someone in blood group B?

Answer 8

Agglutination - this is done as part of cross-matching donor samples after initial antigen tests.

Question 9

What are the two most common blood groups in the UK?

Answer 9

A (42%) and O (47%)

Question 10

What is done before transfusion to check that the donor blood and the recipient’s blood is compatible?

Answer 10

A blood sample is taken from the patient and the ABO blood group is determined (test with anti-A and anti-B antibodies) Select a donor unit of the same group

CROSS-MATCH: patient’s serum is mixed with donor red cells – it should NOT react (if it reacts then it shows that it is incompatible)

Question 11

Which rhesus antigen is the most important?

Answer 11

RhD

Question 12

Describe the inheritance pattern of the RhD antigen.

Answer 12

Autosomal Dominant RhD codes for the D antigen

Question 13

Describe the relative proportions of RhD positive and RhD negative individuals within the population.

Answer 13

RhD positive = 85%

RhD negative = 15%

Question 14

What can happen when RhD negative people are exposed to RhD positive blood?

Answer 14

They become sensitised and can make anti-D antibodies (IgG)

Question 15

What are the implications on future transfusions of an RhD negative individual who has been sensitised to RhD following exposure?

Answer 15

In the future they must be transfused with RhD negative blood or the anti-D antibodies, generated from first exposure, will react with the RhD positive blood This will cause a delayed haemolytic transfusion reaction resulting in anaemia, high bilirubin, jaundice etc.

Question 16

What is haemolytic disease of the newborn?

Answer 16

If an RhD negative mother generates anti-D antibodies following pregnancy with a RhD positive foetus, then if the next foetus is RhD positive, the mother’s anti-D antibodies (IgG) can cross the placenta and cause haemolysis of foetal red blood cells. If severe this can cause hydrops fetalis and death.

Question 17

About 8% of transfused patients will form antibodies against antigens other than ABO and RhD. What are the implications of this?

Answer 17

Once they have formed antibodies against these other antigens, you must use corresponding antigen negative blood in future transfusions otherwise you risk a delayed haemolytic reaction.

Question 18

What must you always do before transfusion in patients who are sensitised to rarer antigens?

Answer 18

Before each transfusion you should test the patient’s blood sample for red cell antibodies. So before transfusing a patient, as well as testing the ABO and RhD groups, you must do antibody screening of their plasma.

Question 19

Why is whole blood no longer routinely given to patients?

Answer 19

It is inefficient

Some components of the blood will degenerate quickly if it is stored as whole blood

Question 20

What three components is blood first separated into via centrifugation?

Answer 20

Plasma
Platelets (and white cells)
Red Cells

Question 21

Why are the red cells concentrated and the plasma removed?

Answer 21

It allows you to avoid fluid overloading, which can precipitate heart failure, when giving someone red cells

Red Cells stored at 4c with 5 weeks shelf life

Question 22

What is fresh frozen plasma (FFP) and what does it contain?

Answer 22

If the plasma is frozen within 6 hours of donation then all the coagulation factors are preserved – this is fresh frozen plasma (FFP)

SHELF LIFE OF 2 YEARS WHEN FROZEN AT -30c, Thawed for 20-30 mins at room temp to preserve coagulation proteins

Question 23

How is cryoprecipitate produced and what does it contain?

Answer 23

Thawing FFP in a 4 degrees centigrade fridge over night produces Cryoprecipitate

It contains: 
Fibrinogen 
Factor 8 
Factor 13 
Von Willebrand Factor 
Fibronectin

Question 24

Explain what fractionation is and why it’s useful.

Answer 24

The plasma of many donors is pooled and put into a fractionating column. This means that various components such as albumin, haemophilia factors and anti-D antibodies can be pulled off.

This is NOT done in the UK.

Question 25

How many donors does it take to make one unit of red blood cells, FFP and Cryoprecipitate?

Answer 25

RBC - 1
FFP -1 (One dose is 3 units however)
Cryoprecipitate - 10

Question 26

Why is it important to know the blood group of the patient before administering the FFP?

Answer 26

You need to know the blood group of the patient to make sure that the antibodies in the FFP don’t react with the recipient’s red blood cell antigens.

If you give the wrong FFP it wont kill the patient because the antibodies are quite dilute but it will haemolyse some of the red cells which is not ideal.

Question 27

What are the indications for FFP?

Answer 27

Bleeding and abnormal coagulation test results (PT and APTT) Reversal of warfarin (e.g. for urgent surgery) – this is because warfarin inhibits factor 2, 7, 9 and 10

Question 28

What are the indications of cryoprecipitate?

Answer 28

If massive bleeding and fibrinogen is very low Rarely - hypofibrinogenaemia

Question 29

How many donors does it take to make one standard adult dose of platelets?

Answer 29

4 donors

Or one donor using Apheresis – cell separator machine (platelet reduced blood is returned to them)

Question 30

How are platelets stored and what is its shelf life?

Answer 30

They are stored at room temperature (22 degrees) and must be constantly agitated to prevent them from aggregating Shelf-life = 5 days (because of risk of bacterial infection)

Question 31

Why is it important to give platelets of the same blood group to patients?

Answer 31

There is no need to X-match but you do need to give platelets of the same ABO blood groups because platelets have low levels of ABO. The wrong group of platelets would be destroyed quickly. Giving platelets of the wrong group could also cause RhD sensitization.

Question 32

What are the indications for giving platelets?

Answer 32

Most haematology patients with bone marrow failure (platelets <10 x 10^9/L)
Massive bleeding
DIC
If very low platelets and the patient needs surgery
If cardiac bypass needed and the patient is on anti-platelet therapy ONE POOL is usually enough

Question 33

If a patient is bleeding post-surgery and his platelet count is normal but he has a prolonged PT and APTT, which component(s) does he need?

Answer 33

FFP

Question 34

If a patient is bleeding post-surgery and his PT and APTT are long and his fibrinogen is low, which component (s) does he need?

Answer 34

FFP and cryoprecipitate

Question 35

State some commonly used fractionation products.

Answer 35

Factor 8 and 9 = used for haemophilia
Factor 8 – also used for von Willebrand’s disease Immunoglobulins:
IM: specific e.g. tetanus, anti-D and rabies
IM: normal globulin – broad mix in the population

Albumin - 4.5% useful in burns, plasma exchanges etc (not indicated in malnutrition so probably overused)

20% salt poor for severe liver and kidney disease only

Question 36

What can IVIg be used to treat?

Answer 36

Pre-op in patients with ITP (immune thrombocytopenic purpura – IVIg helps prevent the destruction of antibody coated platelets in the spleen and liver) and AIHA (autoimmune haemolytic anaemia)

Question 37

What measures are taken to ensure the safety of donated blood?

Answer 37

Exclude high-risk individuals

Test for infections