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Haematology > Blood Transfusion > Flashcards

Blood Transfusion Flashcards

1
Q

What are the reasons for blood transfusion?

A

Mainly due to bleeding

Also due to failure of production

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2
Q

What do blood groups arise from?

A

Antigens

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3
Q

What antigens are expressed on cell surfaces?

A

Red cell antigens

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4
Q

Where can different blood groups be seen?

A

On red blood cells

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5
Q

What blood group has no antigens present on the cell surfaces?

A

Type O

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6
Q

What does the ABO gene encode?

A

Glycosyltransferase

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7
Q

What do A and B genes code for?

A

Transferase enzymes

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8
Q

What is the A antigen?

A

N-acetylgalactosamine

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9
Q

What is the B antigen?

A

Galactose

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10
Q

What kind of allele is the O gene?

A

Non-functional allele

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11
Q

If you are born with blood group A, what will you not form antibodies against?

A

A antigens

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12
Q

What IgM antibodies are naturally occurring?

A

Anti-A/B

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13
Q

What percentage of people are blood group A, B, AB and O?

A

A - 42%
B - 9%
AB - 3%
O - 46%

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14
Q

What is the most common blood group in Europe?

A

O

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15
Q

When is compatibility between red cell donor and recipient fine?

A

When donor is the same blood group as the recipient

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16
Q

What blood type can be given to any blood group and why?

A

Group O can be given to any blood group due to lack of surface antigens

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17
Q

What blood group is the universal recipient for red cells?

A

Group AB - can receive blood from any blood group donor

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18
Q

What blood group is the universal donor for fresh frozen plasma?

A

Group AB

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19
Q

What genotypes in the RhD blood group system are highly homonymous?

A

DD, Dd, dd genotypes

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20
Q

What percentage of the European population will not have the D gene?

A

15%

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21
Q

What genotype is RhD negative?

A

dd

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22
Q

If RhD negative individuals are exposed to RhD positive cells, what can they make?

A

Anti-D

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23
Q

What can anti-D cause?

A

Transfusion reactions or haemolytic disease of the newborn

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24
Q

What is the approach to blood donors?

A 
Extensive behavioural screening 
Age, sex, location 
Tested for ABO and Rh blood groups 
Screened for Hep B, Hep C, HIV and syphilis 
Variably screened for 
- HTLV1
- Hep E 
- West Nile Virus

Apheresis donor
Careful skin cleansing done before

25
Q

What are the fractions of blood and what can they be used for?

A

Plasma - fresh frozen plasma e.g. if you need specific clotting factors, can be transfused directly

Plasma - cryoprecipitate, rich in factor 8 and fibrinogen, used for patients with extensive bleeding to replace fibrinogen in a relatively small volume

Plasma can be further fractionated into factor concentrates e.g. FVIII, FIX

Whole blood - red cells, platelets and plasma

26
Q

How are red cells stored?

A

Stored at 4 degrees C

Shelf life 35 days

27
Q

What are the indications for red cell transfusion?

A

Anaemia
Surgery e.g. obstetric, trauma
Medical e.g. GI haemorrhage, bone marrow failure, chemotherapy
Other e.g. HDN, sickle cell anaemia, thalassaemia

28
Q

What is the dose of platelets?

A

1 unit platelets

29
Q

How are platelets stored?

A

At ambient temperature, around 22 degrees C

Shelf life 5 days

30
Q

Over what time are red cells transfused?

A

2-4 hours

31
Q

Over what time are platelets transfused?

A

20-60 minutes

32
Q

What are the indications for platelet transfusion?

A

Massive haemorrhage - keep platelet count above 75 x 10^9/L

Bone marrow failure - keep platelet count below 10-15 x 10^9 or < 20 x 10^9/L if additional risk e.g. sepsis

Prophylaxis for surgery - minor procedures 50 x 10^9/L, more major surgery 80 x 10^9/L

CNS or eye surgery 100 x 10^9/L

Cardiopulmonary bypass - platelets should be readily available but only used if active bleeding

33
Q

What are the features of practical blood banking?

A 
Blood sent to lab 
Second sample now implemented
Group and save 
Cross match 
Samples kept for 7 days but only valid for 2 days if recent transfusion
34
Q

What are most near-miss incidents with blood transfusion due to?

A

Clinical errors

35
Q

What is involved in blood grouping and antibody screening?

A 
ABO and RhD type 
Checked against historical records
Screen for allo-antibodies in serum 
Tubes then gel columns 
automation
36
Q

What is Coombs test?

A

Test for whether there are antibodies stuck to the surface of RBCs
Used to detect presence of autoantibodies
Direct test - autoimmune haemolytic anaemia, passive anti-D, haemolytic transfusion reactions
Indirect test - used for cross matching

37
Q

What red cells are transfused in minutes, urgent and non-urgent situations?

A

Minutes - O RhD negative red cells, AB plasma

Urgent - type-specific

Non-urgent - full crossmatch, select correct ABO/RhD type, if allo-antibodies choose antigen negative blood

38
Q

What are the key principles of the massive haemorrhage policy?

A

Good communication between all teams is essential
Definitive management - rapid control of bleeding; obstetric intervention, surgery, interventional radiology etc.
Immediate supply of
- 6 units red cells
- 4 units FFP
- 1 unit platelets

39
Q

What are the risks of transfusion?

A

Death or harm
TACO - transfusion associated circulatory overload
TRALI - transfusion related acute lung injury
ATR - acute transfusion reaction
Febrile/allergic
vCJD risk

40
Q

What should the decision to transfuse be based on?

A

Careful assessment of a patient’s clinical state and must be justified as essential to prevent major morbidity or mortality

41
Q

What are the minor reactions to blood transfusion?

A

Fever, usually < 38 degrees C, urticarial rash

Consider paracetamol/antihistamine

42
Q

What are the major reactions to transfusion?

A 
Fever
Urticaria 
Respiratory distress
Hypotension 
Tachycardia 
Oliguria 
Bleeding 
Collapse
43
Q

What is the management of transfusion reactions?

A

Stop transfusion
Check patient identity against component label
Consider - anaphylaxis, circulatory overload, acute haemolytic transfusion reaction, bacterial infection, lung injury etc.

44
Q

What percentage of transfusions result in transfusion associated circulatory overload?

A

1%

45
Q

What is the treatment of TACO?

A

Slow rate
IV diuretic
Oxygen

46
Q

What are the features of ABO haemolytic reaction?

A

Usually catastrophic within 10-20ml of blood transfused
Immediate complement-mediated lysis
Shock, high fever, renal failure

47
Q

What is the management of ABO haemolytic reaction?

A 
O2
IV fluids 
Diuretics
Inotropes
Dialysis

Notify blood service to investigate

48
Q

What are the features of delayed haemolytic reaction?

A

Anaemia and jaundice 7-10 days post-transfusion
Positive direct antiglobulin test
Due to development of antibody

49
Q

What is the management of bacterial infection due to blood transfusion?

A

IV antibiotics
Oxygen
Fluids
Notify blood service

50
Q

What is the management of TRALI?

A

O2/respiratory support
IV fluids
Notify blood service to investigate/initiate recalls

51
Q

What steps were taken to reduce risk of potential transmission of new variant CJD from blood transfusion?

A

Leucodepletion 1998
UK plasma not used for fractionation
Imported FFP for all patients born after 1996

52
Q

What are the features of haemolytic disease of the foetus and newborn?

A

Development of maternal anti-D antibodies
80% chance of having a baby who is RhD positive, possible for these RhD positive cells to cross into the maternal blood
IgG crosses placenta in subsequent pregnancies causing haemolytic anaemia in the foetus
RhD most immunogenic, also c, K, other Rh antigens, Jka and ABO (less immunogenic)
Positive DAT at birth, anaemia and jaundice

53
Q

What are the features of HDN?

A

HPA1A platelet antigen
Much rarer than HDFN
Suspect when isolated thrombocytopenia and bleeding in newborn a few days after birth

54
Q

What is the prevention of HDN?

A

Prophylactic anti-D

  • sensitising events
  • routine at 28/40
55
Q

What is the treatment of HDN?

A

Careful monitoring

  • antibody titres
  • Doppler ultrasound
  • intrauterine transfusions
56
Q

What are the cellular therapies?

A

Leucapheresis

  • bone marrow harvest
  • donor lymphocyte infusions

Other banks

  • bone, milk, tendons, heart valves, faecal
  • islet cells, mesenchymal stem cells

Gene therapies

57
Q

What are the features of TRALI?

A

Transfused anti-leucocyte antibodies in donor plasma interact with patient’s WBC
Bilateral pulmonary infiltrate
Supportive management, ventilation

58
Q

What are the features of post-transfusion purpura?

A

Rare
7-10 days after transfusion
HPA1 negative patient forms antibodies after transfusion or pregnancy
After further transfusion, destruction of own platelets

59
Q

What are the features of transfusion associated graft versus host disease?

A 
Rare but always fatal 
Graft of lymphocytes in donor blood 
- transfused to immunocompromised host 
- homozygosity of donor's HLA type 
Can be prevented by irradiation of blood

Haematology (11 decks)

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