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Haematology > Blood Transfusion > Flashcards

Blood Transfusion Flashcards

1
Q

How much blood and how frequently can one donor give?

A

1 unit (1 pint) every 4 months

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2
Q

What is the name of the glycoprotein and fructose stem/antigen on the red blood cell membrane is common to everyone?

A

H stem

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3
Q

What are A and B antigens?

A

The A and B antigens are made by the addition of a sugar residue onto the common glycoprotein and fructose stem (H stem) - specifically joined onto galactose in addition to the fructose residue

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4
Q

What does the A gene encode?

A

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

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5
Q

What does the B gene encode?

A

An ENZYME that adds galactose to the H stem => B antigen

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6
Q

Describe the inheritance pattern of the ABO blood groups.

A

A and B genes are codominant; if a person is blood group A - genotype could be AA or OA
if a person is blood group B - genotype could be BB or OB
if a person is blood group AB - genotype is AB (both antigens expressed)

O is ‘recessive’ because it doesn’t code for anything at all
So you need to be homozygous for O (OO) to be in blood group O

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7
Q

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

A

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

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8
Q

What class of immunoglobulin are these anti-A/anti-B antibodies?

A

IgM

They are naturally occurring (nearly from birth)

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9
Q

What would happen if someone with anti-B antibodies was given B-positive blood?

A

The anti-A/anti-B antibodies are complete antibodies meaning that it fully activates the complement cascade to cause haemolysis of red cells
This is often FATAL
It can lead to cytokine storm, lysis, cardiovascular collapse and death

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10
Q

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?

A

Agglutination

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11
Q

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

A

A (42%) and O (47%)

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12
Q

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

A

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)

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13
Q

Which rhesus antigen is the most important?

A

RhD

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14
Q

Describe the inheritance pattern of the RhD antigen.

A

Autosomal Dominant
RhD codes for the D antigen

DD or Dd = D antigen expressed
dd = D antigen not expressed

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15
Q

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

A

RhD positive = 85%

RhD negative = 15%

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16
Q

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

A

They become sensitised and can make anti-D antibodies

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17
Q

What type of antibody are anti-D antibodies?

A

IgG

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18
Q

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

A

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.

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19
Q

What is haemolytic disease of the newborn (HDN)?

A

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.

20
Q

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

A

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.

21
Q

What must you always do before transfusion in such patients?

A

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.

22
Q

Why is whole blood no longer routinely given to patients?

A

It is inefficient as patients don’t
need all the ‘components’

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

23
Q

Why are the red cells concentrated and the plasma removed?

A

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

24
Q

What three components (in order of top to bottom) is blood first separated into via centrifugation?

A

Plasma - top
Platelets (and white cells)
Red Cells - bottom

25
Q

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

A

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

26
Q

How is cryoprecipitate produced and what does it contain?

A

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

It contains:

  • Fibrinogen
  • Factor 8
  • Factor 13
  • Von Willebrand Factor
  • Fibronectin
27
Q

Explain what plasma fractionation is and why it’s useful.

A

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.

28
Q

How many donors does it take to make one unit of red blood cells (packed cells, fluid plasma removed)?

A

1

29
Q

How are red blood cells stored and what is their shelf life?

A

Stored in a 4-degree fridge

Shelf-life = 5 weeks

30
Q

How many donors does it take to make one unit of FFP?

A

1 donor for 300ml unit

31
Q

How is FFP stored and what is its shelf life?

A

It is stored at -30ºC

Shelf-life = 2 years

32
Q

How is FFP thawed? When should it be used, and why?

A

It is thawed at room temperature for 20-30 mins before us; If thawed at too high a temperature you could cook the coagulation proteins

You want to use it within half an hour of thawing because the coagulation factors could start to degenerate at room temperature

33
Q

What is the normal dose of FFP?

A

12-15 ml/kg = 3 units

34
Q

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

A

You need to know the blood group of the patient to make sure that theantibodies 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.

35
Q

What are the indications for FFP?

A
  • 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
36
Q

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

A

10 donors

37
Q

What are the indications of cryoprecipitate?

A

If massive bleeding and fibrinogen is very low

Rarely - hypofibrinogenaemia

38
Q

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

A

1 pool of 4 donors

39
Q

What machine can be used to get a standard adult dose from one donor?

A

Apheresis – cell separator machine

40
Q

How are platelets stored and what is its shelf life?

A

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)

41
Q

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

A

There is no need to cross-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.

42
Q

What are the indications for giving platelets?

A
  • Mostly haematology patients with bone marrow failure (if platelets <10 x 109/L)
  • Massive bleeding or acute DIC
  • If very low platelets and patient needs surgery
  • If for cardiac bypass and patient on anti-platelet drugs
  • 1 pool is usually enough - rarely need more
43
Q

If a patient is bleeding post surgery, what components does he need if:

a) His platelet count is normal and his coagulation test (PT and APTT) are prolonged?
b) His PT and APTT are long and his fibrinogen is low?

A

a) FFP

b) FFP and cryoprecipitate

44
Q

State some commonly used fractionation products.

A

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

45
Q

What can IVIg (intravenous immunoglobulin) be used to treat?

A

Pre-op in patients with ITP and AIHA (autoimmune haemolytic anaemia)

(immune thrombocytopenic purpura – IVIg helps prevent the destruction of antibody coated platelets in the spleen and liver)

46
Q

What is albumin used to treat?

A

4.5% = useful in burns, plasma exchanges etc.

20% (salt poor) = for certain severe liver and kidney conditions only.

47
Q

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

A

Exclude high-risk individuals

Test for infections

Haematology (11 decks)

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