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Y2 - HAEM > Blood Transfusion > Flashcards

Blood Transfusion Flashcards

1
Q

When should we give blood?

A
  • When no safer alternative
  • Massive bleeds - when fluids are insufficient
  • Anaemic patients - if iron / B12 / folate insufficient
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2
Q

Structurally, what does it mean to be of the A , B , O blood groups?

A
  • There is always a H stem on red cell membranes, in O group, there is only this. There is no sugar on the glycoprotein / fucose chain
  • There may be A and B stems too. These A and B antigens are formed by adding certain sugar molecules to the glycoprotein / fucose chain (the chain is common to all stems but the chain is the same essentially as the H stem)
  • A stem / antigen coding for N-acetyl galactosamine transfersase - so has N-acetyl galactosamine conjugated to the glycoprotein / fucose chain
  • B stem / antigen coding for galactose transferase so has galactose conjugated to the glycoprotein / fucose chain
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3
Q

How are the A, B, O blood groups coded for genetically?

A
  • Gene for A: encodes N-acetyl glucosamine transferase which conjuagates on N-acetyl glucosamine onto the glycoprotein / fucose chain stem
  • Gene for B: encodes glucosamine transferase which conjugates on glucosamine onto the glycoprotein / fucose chain stem
  • A and B genes are co-dominant
  • The O group is recessive
  • Some people carry O gene and A / B but because its recessive while A / B are dominant, they’ll be either A / B blood groups
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4
Q

Outline what the antibodies are against blood groups, which ones circulate in which people, antigen (blood group) and antibody interaction and so what would happen if you give the wrong blood group transfusion

A
  • IgM antibodies
  • We have antibodies against all the blood group antigens we don’t express e.g. if we’re blood group O, we have anti-A and anti-B antibodies
  • They would bind the antigens on the red cell membranes to activate the complement cascade and also cause red cell agglutination
  • If you give the wrong transfusion e.g. give group A to someone who is group O, the antibody-antigen interactions could be fatal
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5
Q

if you’re blood group O, what antigens do you have on the red cell?

A
  • None
  • You have the H stem but this isn’t an antigen
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6
Q

If you’re blood group AB, which blood antibodies will you have in the blood?

A
  • None
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7
Q

How to test what blood group someone is when we don’t know and how to test to see whether donor’s blood compatible / incompatible?

A
  • Either take the the patient’s serum and cells (whole blood) and add known anti-B / anti-A reagents and check for agglutination thereby telling us the blood group
  • OR
  • X-match: patient’s serum mixed with donor red cells – if we see agglutination, it is incompatible
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8
Q

Is the gene for RhD recessive or dominant?

A

Dominant

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9
Q

What type of antibodies are anti-RhD antibodies?

A

IgG

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10
Q

Discuss what / when ( RhD blood) antibodies are present in RhD negative patients

A
  • None normally
  • BUT when sensitised (upon exposure) to D positive (RhD+) blood, anti-D antibodies are formed
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11
Q

Complete the table

A
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12
Q

1) Discuss when you can get possible dangers with transfusions in RhD negative people, and why they may not be fatal to the patient
2) Then explain risks to the foetus - including the name of the complication, and why this may be fatal to the foetus

A

1)

  • If RhD- patients are exposed to D antigens in RhD+ blood (transfuse RhD+ blood in), then they create anti-D antibodies
  • Upon NEXT EXPOSURE, these anti-D antibodies will react against the RhD+ antibodies, however this is not fatal because the anti-D bodies are IgG so the whole complement cascade is not activated
  • The antibody-antigen reaction causes slow extravascular haemolysis → leading to anaemia due to haemolysis and jaundice due to high BR from haemolysis

2)

  • HDN = Haemolytic disease of the new-born
  • If RhD- mother is given RhD+ transfusion, she will create anti-D antibodies
  • If in her next pregnancy, the baby is RhD+, then these anti-D bodies will cross the placenta and there will be a antibody-antigen reaction which will cause haemolysis of red cells
  • If this haemolysis is severe, hydrops fetalis may occur….
  • Anaemia in the newborn and more importantly, jaundice so high BR due to haemolysis, baby cannot cope and BR crosses BBB, causing brain damage and death
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13
Q

What blood should we transfuse to avoid complictions in RhD- patients or when we are unsure of the Rh blood group?

A
  • Transfuse blood of the same RhD group (there is no harm giving RhD negative blood to a positive patient)
  • O negative used as an emergency blood when patient’s blood group not known
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14
Q

Once have formed antibody must use ….. ….. ….. ….. ; or else risk of delayed haemolytic reaction (can be severe)

A

corresponding antigen negative blood

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15
Q

How do we know if patient will need antigen negative blood? Apart from testing blood group

A
  • Do an ‘antibody screen’ to see what antibodies are present
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16
Q

How is the donated blood split up, and into what?

A
  • Centrifugation then different components rae extracted into satellite bags
  1. Red cells
  2. Plasma (antibodies and coagulation factors)
  3. Buffy coat (WBCs and platelets)
17
Q

How much blood is taken from donors?

A
  • 1 unit
18
Q

What apparatus is used to deliver blood and what does it contain for safety?

A
  • Blood giving set
  • Filter to remove clumps / debris from storage
19
Q

We rarely use frozen red cells. Give a weakness of using them

A
  • Poor recovery on thawing
  • Every time you freeze and thaw, you lose up to half the dose
20
Q

Why must fresh frozen plasma be frozen?

A

To preserve the coagulation factors

21
Q

What dose of FFP (fresh frozen plasma) do we give?

A
  • 12-15 ml / kg
  • Usually 3 units
22
Q

1) When do we give FFP?
2) For what do we NOT give FFP?

A

1)

  • Patients bleeding due to abnormal coagulation factors - abnormal coagulation test results PT, APPT
  • To reverse warfarin anticoagulant e.g. for surgery when PCC is unavailable

2)

  • NOT for just volume replacement
23
Q

What is PCC and why is it preferable to use PCC than FFP (fresh frozen plasma) to reverse warfarin e.g. prior to surgery?

A
  • Prothrombin complex concentrate
  • Smaller volume needed so it can enter the patient more rapidly - more rapid effect
  • It must be fractionated and so it must be subject to heat treatment and viral inactivation - thereby making it safer in that there is a lower risk of viral infection than with FFP
24
Q

1) How is cryoprecipitate formed / what is it formed from?
2) What does cryoprecipitate contain ?

A

1)

  • When FFP (fresh frozen plasma) is thawed slowly
  • There is precipitate at the bottom, and liquid on top – the precipitate is cryoprecipitate

2)

  • Fibrinogen and FVIII
25
Q

When is cryoprecipitate used aka what are its indications?

A
  • In massive bleeding events, where fibrinogen is very low
  • Can be used when fibrinogen is very low e.g. in hypofibrinogenaemia
26
Q

Why must we give the same group platelets as well when giving platelets?

A
  • Because even platelets have a very low level of A,B,O blood antigens so they would be destroyed if attacked
  • Also can cause RhD sensitisation due to RBC contamination
27
Q

When do we provide platelets therapeutically?

A
  • Bone marrow failure
  • Massive bleeding
  • Acute DIC
  • Before surgery if low platelets
  • If cardiac surgery and the patient is on anti-platelets
28
Q

What are the various fractionation products (large pool)?

A
  • FVIII, FIX
  • Immunoglobulins
  • Albumin
29
Q

Why are FVIII, FIX as part of the fractionated products useful - i.e. when is their use indicated?

A
  • FVIII / FIX or haemophilia A / B respectively
  • FVIII for vWF
30
Q

Why are immunoglobulins, as part of the fractionated products useful and how are they administered?

A
  • IM: Specific: tetanus, anti-D, rabies
  • IM: Normal globulin: broad mix of antibodies from the population (e.g. Hep. A Virus)
  • IV Ig: broad mix of antibodies, pre-operative in patients with ITP or AIHA (autoimmune disease)
31
Q

Why is albumin as part of the fractionated products useful, as in what is it indicated for, and at what concs?

A

4.5%

  • Burns where there’s loss of fluid
  • Plasma exchanges

20% - salt poor

  • Certain liver and kidney problems
  • The kidneys become porous → proteins excreted → poor oncotic pressure. SO, albumin prevents this poor oncotic pressure
32
Q

What infections should you check for in prospective donors which would mean they can’t donate?

A

* Hep. B – HbsAg, PCR

* Hep. C – anti-HCV, PCR

* HIV, anti-HIV, PCR

* HTLX, anti-HTLV

* Syphilis – TPHA (spirochete)

* Hep. E – PCR

* Some also tests for CMV virus – often harmless but risky for babies and foetuses

33
Q

Why can you sometimes not be completely sure if the prospective donor is clear of infection

A
  • Time window idea for when you can test and find signs of infection
34
Q

What does leucodepleted mean and why might all blood components be leucodepleted in some transfusions?

A
  • Free of WBCs
  • In case you can trasmit infection e.g. variant prion CJD via WBCs

Y2 - HAEM (11 decks)

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