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Yr 2 MCD - Haem > 11 - Blood Transfusion > Flashcards

11 - Blood Transfusion Flashcards

1
Q

Where does blood for transfusions come from?

A

Human source

No synthetics yet

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2
Q

Why is blood a scarce resource?

A

1 donor gives approximately 1 pint, maximum every 4 months

Need 9,000 units of blood per day in the UK

Can’t stockpile blood due to its 5 week shelf-life

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3
Q

What is the shelf-life of donated blood?

A

5 weeks

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4
Q

Whose decision is it to transfuse blood in certain situations?

A

A doctor always has to prescribe it

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5
Q

In what situations is blood transfused?

A

When no safer alternative

e. g. In massive bleeding and ‘plain fluids’ are not sufficient
e. g. If anaemia and iron/B12/folate are not appropriate

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6
Q

Who discovered ABO blood groups?

A

Landsteiner in 1901

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7
Q

What has to occur before a person has their blood transfusion?

A

Test blood groups of patient and donor. Then X-match

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8
Q

What should not occur if a patient and donor are not ABO compatible?

A

Patient should not die of ABO 
incompatible blood 
transfusion 


Yet a death and several in ITU each year in UK

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9
Q

Which are the most important of all blood groups?

A

ABO Blood Groups

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10
Q

How are A and B antigens on RBCs formed?

A

Formed by adding one or other sugar residue onto a common glycoprotein and fucose stem on red cell membrane

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11
Q

What is the difference between Group O compared to Groups A and B?

A

Group O has neither A or B sugars

It has the fucose stem only

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12
Q

How are the type of antigens on a person’s RBCs determined?

A

Antigens are determined by corresponding genes

A gene codes for enzyme which adds N-acetyl galactosamine to common glycoprotein and fructose stem

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13
Q

Which enzyme is coded for the B gene?

A

B gene codes for enzyme which adds galactose

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14
Q

What is the pattern of inheritance of the O gene?

A

Recessive

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15
Q

For a person with blood group A, what genes could they have inherited?

A

AA or OA

Because O is recessive

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16
Q

What is different for a person that inherits both A and B genes?

A

A and B genes are co-dominant

Therefore, person will have A and B antigens

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17
Q

Which blood antibodies do people have?

A

Person has antibodies against any blood antigen that is not present in their own red cells

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18
Q

Which antibody is naturally occurring nearly from birth?

A

IgM

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19
Q

What kind of antibody is IgM?

A

It is a ‘complete’ antibody

Therefore, it fully activates complement cascade to cause haemolysis of red cells

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20
Q

What happens in patient with corresponding antibody who receives ABO incompatible transfusion?

A

For example:

Person with Group O

Receives blood group A

This person will have anti-A and anti-B antibodies in their own body

This antibody/antigen interaction often fatal

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21
Q

What occurs at a cellular level in an ABO incompatible transfusion?

A

IgM antibodies interacts with corresponding antigen to cause agglutination

For example:

Person with blood group B

Receives group A

Has anti-A antibody in their plasma naturally, group A cells are added via transfusion

Agglutination occurs

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22
Q

What is the frequency of people who are Blood Group A in the UK?

A

42%

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23
Q

What is the frequency of people who are Blood Group B in the UK?

A

8%

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24
Q

What is the frequency of people who are Blood Group O in the UK?

A

47%

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25
Q

What is the frequency of people who are Blood Group AB in the UK?

A

3%

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26
Q

What antigens are on the red cells of people with Blood Group A?

A

A antigens

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27
Q

What antigens are on the red cells of people with Blood Group B?

A

B antigens

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28
Q

What antigens are on the red cells of people with Blood Group O?

A

No antigens

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29
Q

What antigens are on the red cells of people with Blood Group AB?

A

A and B antigens

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30
Q

What antibodies are in the plasma of people with Blood Group A?

A

Anti-B

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31
Q

What antibodies are in the plasma of people with Blood Group B?

A

Anti-A

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32
Q

What antibodies are in the plasma of people with Blood Group O?

A

Anti-A and Anti-B

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33
Q

What antibodies are in the plasma of people with Blood Group AB?

A

No antibodies

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34
Q

How do you test a patient’s blood group before they receive a blood transfusion?

A

Take patient blood sample
- plasma and cells

Test ABO group
- test with known anti-A and anti-B reagents

Select donor unit of same group
- antigen matched

Then X-match

  • patient’s serum mixed with donor red cells
  • should not react
  • if it reacts (agglutination), then they are incompatible
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35
Q

What is the most important RH Group?

A

RhD is the most important

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36
Q

What percentage of people are RhD positive or negative?

A

RhD positive = 85%

RhD negative = 15%

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37
Q

What antigen do RhD positive people have?

A

D antigen

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38
Q

What are the genes for RhD groups?

A

D
- codes for D antigen on red cell membrane

d
- codes for no antigen and is recessive

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39
Q

For a person with genotype dd, would they be RhD positive or negative?

A

RhD negative

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40
Q

For a person with genotype Dd, would they be RhD positive or negative?

A

RhD positive

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41
Q

For a person with genotype DD, would they be RhD positive or negative?

A

RhD positive

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42
Q

How are patient’s ABO and RhD groups typically stated?

A

Shortened

e.g.

O positive =
ABO group O and RhD positive

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43
Q

How can people without RhD antigen still produce anti-D antibodies?

A

After they are exposed to RhD antigen

- either by transfusion of RhD positive blood or pregnancy with RhD positive foetus

44
Q

What type of antibody are Anti-D antibodies?

A

IgG antibodies

45
Q

What type of antibody are Anti-A and Anti-B antibodies?

A

IgM antibodies

46
Q

What antigens and antibodies does a RhD positive person have?

A

Antigens
- D antigens

Antibodies
- no anti-D antibodies

47
Q

Can people with the RhD gene ever make anti-D antibodies after exposure?

A

No

Unless pathological

48
Q

What antigens and antibodies does a RhD negative person have?

A

Antigens
- no D antigens

Antibodies

  • no anti-D antibodies
  • Can make anti-D if exposed
49
Q

Do people who are RhD have negative Anti-D antibodies?

A

No, not unless they have been exposed and therefore sensitised

50
Q

In what two situations does having Anti-D antibodies cause issues?

A

Future Transfusion

Haemolytic Disease of the Newborn (HDN)

51
Q

What are the implications of having Anti-D antibodies for future transfusions?

A

Must have RhD negative blood

Otherwise, Anti-D will react with D antigens in RhD positive blood

Causes delayed haemolytic transfusion reaction
- anaemia
- high bilirubin
- jaundice 
etc.
52
Q

Explain the mechanism of HDN

A

Haemolytic Disease of the Newborn (HDN)

Example:
RhD negative mother has Anti-D

Next Pregnancy, foetus is RhD positive

Mother’s IgG anti-D antibodies cross placenta

Causes haemolysis of foetal red cells

If severe:

  • hydrops fetalis
  • death
53
Q

What is hydrops fetalis?

A

A condition in the foetus characterised by an accumulation of fluid (oedema) in at least two foetal compartments.

54
Q

What is the most important thing to remember when transfusing RhD positive blood?

A

Avoid RhD negative patients making RhD antibodies due to exposure

Transfuse blood of same RhD group

55
Q

Why should giving RhD negative blood to a RhD positive patient be avoided?

A

It is wasteful

RhD negative can be given to both RhD positive and negative, so is better to save it for emergencies

Try to give RhD positive blood to patients who are RhD positive

56
Q

What blood is used for emergencies?

A

O negative

ABO = Group O 
RhD = negative
57
Q

What percentage of donors are O negative?

A

6-7%

58
Q

What are some examples of other antigens that can be present on red blood cells but aren’t routinely matched for?

A

Rh Group:

  • C
  • c
  • E
  • e
Others:
- Kelly
- Duffy
- Kidd
etc.
59
Q

What percentage of pints of blood transfused will form antibodies for antigens that aren’t routinely matched for?

A

8% of pints transfused

60
Q

Once a person has formed antibodies for certain antigens in blood, what must be accounted for in next transfusion?

A

Must use corresponding antigen negative blood

Otherwise you risk a delayed haemolytic reaction that can be severe

61
Q

How do you know if a patient needs antigen negative blood?

A

BEFORE each transfusion episode, test patient’s blood sample for red cell antibodies

Therefore, before transfusing patient, as well as testing their ABO and RhD group, must do an ‘antibody screen’ of their plasma

62
Q

How is blood collected?

A

1 unit (a pint) of blood collected into a bag containing anticoagulant

63
Q

What is no longer routine practice in blood transfusion?

A

No longer routinely give whole blood patients

- just give parts needed

64
Q

Why are patients not routinely given whole blood anymore?

A

More efficient
- less waste as patients don’t need all the components

Degeneration
- some components degenerate quickly if stored as whole blood

65
Q

When patients need red cells, how are they now routinely delivered?

A

Plasma removed and conserved for someone else

Red cells are therefore concentrated and also helps to avoid fluid overloading the patient

66
Q

How is blood split into its different components for use separately?

A

Centrifuge one unit of blood

Plasma = TOP
Platelets = MIDDLE
Red Cells = BOTTOM

Squeeze each layer into satellite bags

Cut them free

CLOSED SYSTEM

67
Q

What are the different uses of plasma?

A

Fresh Frozen Plasma (FFP)

Cyroprecipitate

Plasma for Fractionation (not UK)
- albumin {factor VIII; IX immunoglobulins, anti-D etc}

68
Q

What is the shelf-life of red cells and how are they stored?

A

5 weeks

Stored at 4 degrees in a fridge

69
Q

Outline the use of red cells

A

1 unit from 1 donor

  • ‘packed cells’
  • fluid plasma removed

Give through a ‘blood giving set’
- has filter to remove clumps/debris

Rarely need frozen red cells

  • from National Frozen Bank
  • for rare groups/antibodies
  • poor recovery on thawing
70
Q

What are frozen red cells used for?

A

For people with rare groups/antibodies

71
Q

What is the disadvantage of using frozen red cells?

A

Poor recovery on thawing

72
Q

What is the shelf-life of FFP and how is it stored?

A

2 year shelf-life

Stored at -30 degrees

Frozen within 6 hours of donation to preserve of coagulation factors

73
Q

How big is one unit of FFP?

A

1 unit from 1 donor

300ml

Can get small packs for children

74
Q

What must be done before use of FFP?

A

Must thaw before use
- for approx. 20-30 minutes

If too hot, the proteins cook

Give ASAP

  • ideally within 1 hour
  • or else, coagulation factors degenerate at room temperature
75
Q

What is the typical dose of FFP?

A

Dose = 12-15ml/kg

Usually about 3 units

76
Q

How do you match FFP to patient in need?

A

Need to know blood group

No X-match
- just choose same blood group

Do this because it contains ABO antibodies, could cause a bit of haemolysis

77
Q

What are the indications for FFP?

A

If bleeding + abnormal coagulation test results (PT, APTT)

  • monitor response
  • clinically and by coagulation tests

Reversal of warfarin (anticoagulant)
- e.g. for urgent urgent if PCC is not available

Other conditions occasionally

NOT JUST TO REPLACE VOLUME/FLUID LOSS

78
Q

What is the shelf-life of Cryoprecipitate and how is it stored?

A

2 year shelf-life

Stored at -30 degrees

79
Q

What must be done prior to use of Cryoprecipitate?

A

Thaw at 4-8 degrees overnight

80
Q

What is the standard dose of Cryoprecipitate?

A

From 10 donors (5 in a pack)

81
Q

What does Cryoprecipitate contain?

A

Fibrinogen and factor VIII

82
Q

What are indications for Cryoprecipitate?

A

If massive bleeding and and fibrinogen very low

Hypofibrinogenaemia (very rare)

83
Q

What is the shelf-life for Platelets and how are they stored?

A

5 day shelf-life

Stored at 22 degrees (room temperature)

They are constantly agitated

84
Q

How do match platelets to a patient in need?

A

Need to know blood group

No X-match

  • just choose same group
  • as platelets have low levels of ABO antigens on them
  • therefore, wrong group would be destroyed quickly
85
Q

What does X-match mean?

A

Cross-match

86
Q

Could platelet transfusion cause RhD sensitisation?

A

Yes and this is because platelets are sometimes contaminated with some red cells

These red cells could be RhD positive

87
Q

Would does RhD sensitisation mean?

A

This means exposure of a RhD negative person to RhD positive blood cells

88
Q

What are the indications for platelet use?

A

Most patients with bone marrow failure
- if platelets <10x10^9/L

Massive bleeding or acute DIC

Very low platelets and patient needs surgery

For cardiac bypass and patient is on anti-platelet drugs

89
Q

What is DIC?

A

Disseminated Intravascular Coagulation

A condition in which small blood clots develop throughout the bloodstream, blocking small blood vessels.

90
Q

What is the standard adult dose of platelets?

A

1 pool from 4 donors

OR

From 1 donor by apheresis (cell separator machine)

91
Q

What is the risk of using platelets past their 5 day shelf-life date?

A

Risk of bacterial infection

92
Q

What products are fractionated out of blood (not in the UK)?

A

Factor VIII and IX

Immunoglobulins

93
Q

Why are Factor VIII and IX fractionated out of blood?

A

Haemophilia A and B respectively (males)

Factor VIII for Willebrand’s Disease

94
Q

Why are fractionated recombinant factor VIII and IX not in common use?

A

Fractionation is an expensive method

95
Q

Why are Factor VIII and IX sometimes fractionated out of blood?

A

Haemophilia A and B respectively (males)

Factor VIII for Willebrand’s Disease

96
Q

Why are certain immunoglobulins sometimes fractionated out of blood?

A

IM

  • tetanus
  • anti-D
  • rabies

IM

  • normal globulin
  • broad mix in population (e.g. HAV)

IVIg
- pre-op in patients with ITP or AIHA

97
Q

What are the uses of albumin?

A
  1. 5%
    - useful in burns, plasma exchanges etc
    - probably overused (not indicated in malnutrition)

20%

  • salt poor
  • for certain severe liver and kidney conditions only
98
Q

How is the safety of donated blood ensured for patients?

A

Testing for some infections (not fail safe)

Questioning for risk behaviour (to exclude these people)

99
Q

How is safety of blood donors ensured?

A

Ask questions to prevent blood donation causing harm

- e.g. people with cardiac issues

100
Q

What infections must blood donors be tested for?

A

Hepatitis B

  • HBsAg
  • PCR

Hepatitis C

  • anti-HCV
  • PCR

HIV

  • anti-HIV
  • PCR
101
Q

What infections must blood donors be tested for?

A

Hepatitis B [virus]

  • HBsAg
  • PCR

Hepatitis C [virus]

  • anti-HCV
  • PCR

HIV [virus]

  • anti-HIV
  • PCR

HTLV [virus]
- anti-HTLV

Syphilis
- TPHA (spirochete)

Hepatitis E
- PCR

  • Some also tested for CMV [virus]
102
Q

Why can we not rely only on testing the blood of donors for infection to ensure blood safety?

A

“Window Period” of infections

- tests will not show up positive

103
Q

Other than infection testing, how else can we try and ensure blood safety for patients?

A

Exclude high risk donors

Use voluntary, unpaid donors

Use questionnaire to try and exclude other infections such as malaria

104
Q

What are Prion Diseases?

A

Prion Disease - vCJD

A group of uniformly fatal neurodegenerative diseases characterised by progressive dementia and motor dysfunction.

These diseases occur in spontaneous, genetic, and acquired forms.

CAN BE TRANSMITTED BY BLOOD TRANSFUSION

105
Q

What is done as a precaution against Prion Diseases?

A

All plasma pooled to make fractionated products now obtained from USA (UK plasma - some used for FFP, the rest thrown away)

All blood components have white cells filtered out (leucodepleted)
- in case white cells are essential for uptake of vCJD prion into brain to cause disease

106
Q

What does the ‘fingerpick’ test estimate?

A

It estimates Hb (not iron)

Yr 2 MCD - Haem (12 decks)

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