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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
What are the fractions of blood and what can they be used for?
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
How are red cells stored?
Stored at 4 degrees C | Shelf life 35 days
27
What are the indications for red cell transfusion?
Anaemia Surgery e.g. obstetric, trauma Medical e.g. GI haemorrhage, bone marrow failure, chemotherapy Other e.g. HDN, sickle cell anaemia, thalassaemia
28
What is the dose of platelets?
1 unit platelets
29
How are platelets stored?
At ambient temperature, around 22 degrees C | Shelf life 5 days
30
Over what time are red cells transfused?
2-4 hours
31
Over what time are platelets transfused?
20-60 minutes
32
What are the indications for platelet transfusion?
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
What are the features of practical blood banking?
``` 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
What are most near-miss incidents with blood transfusion due to?
Clinical errors
35
What is involved in blood grouping and antibody screening?
``` ABO and RhD type Checked against historical records Screen for allo-antibodies in serum Tubes then gel columns automation ```
36
What is Coombs test?
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
What red cells are transfused in minutes, urgent and non-urgent situations?
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
What are the key principles of the massive haemorrhage policy?
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
What are the risks of transfusion?
Death or harm TACO - transfusion associated circulatory overload TRALI - transfusion related acute lung injury ATR - acute transfusion reaction Febrile/allergic vCJD risk
40
What should the decision to transfuse be based on?
Careful assessment of a patient's clinical state and must be justified as essential to prevent major morbidity or mortality
41
What are the minor reactions to blood transfusion?
Fever, usually < 38 degrees C, urticarial rash | Consider paracetamol/antihistamine
42
What are the major reactions to transfusion?
``` Fever Urticaria Respiratory distress Hypotension Tachycardia Oliguria Bleeding Collapse ```
43
What is the management of transfusion reactions?
Stop transfusion Check patient identity against component label Consider - anaphylaxis, circulatory overload, acute haemolytic transfusion reaction, bacterial infection, lung injury etc.
44
What percentage of transfusions result in transfusion associated circulatory overload?
1%
45
What is the treatment of TACO?
Slow rate IV diuretic Oxygen
46
What are the features of ABO haemolytic reaction?
Usually catastrophic within 10-20ml of blood transfused Immediate complement-mediated lysis Shock, high fever, renal failure
47
What is the management of ABO haemolytic reaction?
``` O2 IV fluids Diuretics Inotropes Dialysis ``` Notify blood service to investigate
48
What are the features of delayed haemolytic reaction?
Anaemia and jaundice 7-10 days post-transfusion Positive direct antiglobulin test Due to development of antibody
49
What is the management of bacterial infection due to blood transfusion?
IV antibiotics Oxygen Fluids Notify blood service
50
What is the management of TRALI?
O2/respiratory support IV fluids Notify blood service to investigate/initiate recalls
51
What steps were taken to reduce risk of potential transmission of new variant CJD from blood transfusion?
Leucodepletion 1998 UK plasma not used for fractionation Imported FFP for all patients born after 1996
52
What are the features of haemolytic disease of the foetus and newborn?
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
What are the features of HDN?
HPA1A platelet antigen Much rarer than HDFN Suspect when isolated thrombocytopenia and bleeding in newborn a few days after birth
54
What is the prevention of HDN?
Prophylactic anti-D - sensitising events - routine at 28/40
55
What is the treatment of HDN?
Careful monitoring - antibody titres - Doppler ultrasound - intrauterine transfusions
56
What are the cellular therapies?
Leucapheresis - bone marrow harvest - donor lymphocyte infusions Other banks - bone, milk, tendons, heart valves, faecal - islet cells, mesenchymal stem cells Gene therapies
57
What are the features of TRALI?
Transfused anti-leucocyte antibodies in donor plasma interact with patient's WBC Bilateral pulmonary infiltrate Supportive management, ventilation
58
What are the features of post-transfusion purpura?
Rare 7-10 days after transfusion HPA1 negative patient forms antibodies after transfusion or pregnancy After further transfusion, destruction of own platelets
59
What are the features of transfusion associated graft versus host disease?
``` 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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