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Haematology > Blood Transfusion > Flashcards

Blood Transfusion Flashcards

1
Q

Where is obtained from?

A

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

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2
Q

What is the shelf life of blood?

A

5 weeks

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3
Q

When do we use blood transfusions?

A

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

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4
Q

What are ABO blood groups?

A

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.

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5
Q

What do Group A and B have attached to them?

A

A – N-acetyl galactosamine

B – Galactose

*the genes code for enzymes that attach the sugars

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6
Q

Describe the inheritance patterns of ABO blood groups

A

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

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7
Q

What is the universal donor and universal reciever?

A

OO- is the universal donor

AB+ is the universal receiver

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8
Q

Why is giving someone the wrong blood dangerous?

A
  • 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
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9
Q

How is a person’s blood tested for group?

A
  • 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
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10
Q

What are RhD blood groups?

A

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

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11
Q

Is the Rhd gene dominant/recessive?

A

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

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12
Q

What % of people are RhD positive and negative?

A

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

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13
Q

How are blood groups expressed?

A

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

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14
Q

What is anti-D?

A

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.

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15
Q

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

A

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.

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16
Q

What is haemolytic disease of the newborn?

A

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.

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17
Q

Which blood group is used in an emergency?

A

O- blood

18
Q

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

A

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.

19
Q

What is hydrops fetalis?

A

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

20
Q

What are some other red cell groups?

What must be ensured following transfusion with an opposite AB?

A
  • 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”
21
Q

Why are blood components transfused?

A

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

22
Q

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

A

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

23
Q

How are red cells stored and given?

A
  • 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
24
Q

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

A
  • 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
25
Q

How is blood collected?

A

Collected in a bag containing anticoagulant

26
Q

When is FFP given?

A
  • Bleeding and abnormal coagulation test results (PT and APTT)
  • Reversal of warfarin (anticoagulant) for urgent surgery
27
Q

What is cryoprecipitate?

A
  • 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
28
Q

How is cryoprecipitate stored and what is the dose?

A
  • Same as FFP: store at -30oC for 2 years

- Standard dose = from 10 donors (5 in a pack)

29
Q

When is cryoprecipitate used?

A
  • 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)
30
Q

What is the adult standard dose of platelets?

A

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

31
Q

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

A
  • 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
32
Q

When are platelets given?

A
  • Bone marrow failure
  • Massive bleeding (or DIC)
  • Surgery (patient has low platelets) or cardiac bypass (patient on anti-platelet drugs)
33
Q

What are fractionated products?

A

The fractioned products are taken from a large pool (1000s) of donors and mixed and then fractioned off.

  • Factor 8 and 9
  • Immunoglobulins
  • Albumin
34
Q

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

A
  • 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
35
Q

When are immunoglobulins used?

A

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)

36
Q

When is albumin used?

A

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)

37
Q

How are patients protected from dangerous blood?

A
  • 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
38
Q

What is all blood tested for?

A
  • Hepatitis B and C
  • HIV
  • HTLV – Human T-Lymphotropic Virus
  • Syphilis
  • CMV or HEV
39
Q

What is the window period?

A

“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.

40
Q

How is the window period dealt with?

A

Exclude high-risk donors and use voluntary, unpaid donors

41
Q

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

A
  • The abnormal folding of the prion proteins leads to brain damage
  • Can be transmitted by blood transfusion
42
Q

What precautions are taken to avoid vCJD?

A

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).

Haematology (11 decks)

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