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Haematology > Transfusions > Flashcards

Transfusions Flashcards

1
Q

What is the minimum criteria that blood donors must meet?

A

Hb 135g/l in men and 125g/l in women

Weight at least 50kg

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2
Q

How is the safety of blood donations ensured?

A

Donor selection questionnaire

Take contact details in case donor becomes unwell after donation

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3
Q

Where are all the blood donations taken in Scotland processed?

A

SNBTS headquarters in Edinburgh

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4
Q

How is blood processed when it is taken to the blood labs?

A

Bag of whole blood centrifuged to separate into component parts
Undergo microbiological testing = HIV, Hep B/C/E, HTLV, syphilis

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5
Q

What components is blood separated into?

A

Red cell = stored at 4 degrees for 35 days
FFP = stored at -30 degrees for 3 years
Platelets = stored at 22 degrees for 7 days with agitation (shaken gently)

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6
Q

What blood products are available from the transfusion lab?

A

Blood components = red cells, FFP, platelets, cryoprecipitate
Blood products = anti-D Ig, prothrombin complex concentrate
Pharmacy products = IV Ig, human albumin, specific Ig

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7
Q

What determines blood groups?

A

Red cell antigens = contained within cell membrane

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8
Q

What are the two most important blood group systems?

A

ABO system = encoded by ABO gene

Rh system = encoded by RhD and RhCE genes

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9
Q

Where is the ABO gene located?

A

On chromosome 9

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10
Q

What is the inheritance of the ABO gene?

A

Receive one from each parent

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11
Q

What do A and B genes code for?

A

Transferases = modify precursor called H substance on the red cell membrane

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12
Q

What does inheritance of a B gene cause?

A

Expression of a B antigen

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13
Q

What is the expression of different ABO groups?

A

A and B are dominant over O but are co-dominant with each other
O is silent = no O antigen (merely lack of A or B)

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14
Q

What is the phenotype of a blood group?

A

Which antigens are expressed (e.g group A)

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15
Q

What is the genotype of a blood group?

A

Which genes are present (e.g AA or AO)

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16
Q

What genotypes are the different ABO phenotypes?

A

Group O = OO
Group A = AA or AO
Group B = BB or BO
Group AB = AB

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17
Q

What is Landsteiner’s law?

A

When an individual lacks A or B antigen the corresponding antibody is produced in their plasma

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18
Q

What does Landsteiner’s law cause in practice?

A

Naturally occurring antibodies cause haemolysis of red cells expressing the specific antigen

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19
Q

What are the antibodies associated with different ABO blood groups?

A

Group A = anti-B antibody
Group B = anti-A antibody
Group AB = neither
Group O = anti-A and anti-B antibodies

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20
Q

If a blood donor is group O, which recipient blood groups will it be compatible with?

A

Groups O, A, B and AB

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21
Q

What is the only blood group that a donor sample that is blood group AB will be compatible with?

A

Group AB

22
Q

What are blood groups will a donor sample that is group A be compatible with?

A

Groups A and AB (group B is compatible with B and AB)

23
Q

How common is RhD+ status in the population?

A

Occurs in 85% of the population

24
Q

What are the alleles of the Rhesus system?

A

2 alleles = D and d
One inherited from each parent
d is silent

25
Q

What are the genotypes associated with the different Rh system phenotypes?

A 
Rh+ = DD or Dd
Rh- = dd
26
Q

Why is the Rh system important?

A

RhD antigen is very immunogenic

27
Q

What is the clinical relevance of anti-D antibody?

A

Can cause transfusion reactions and haemolytic disease of the newborn

28
Q

What kind of blood should RhD- patients receive?

A

RhD- blood = must avoid exposing them to D antigens

29
Q

What are the aims of pre-transfusion testing?

A

Identify ABO and RhD group of patient

Identify presence of clinically significant red cell antibodies

30
Q

How is ABO grouping carried out?

A

Using forward and reverse testing

31
Q

What occurs in forward ABO grouping?

A

Reagents called antisera with known specific antibody used to identify antigens present on red cells

32
Q

What occurs in reverse ABO grouping?

A

Reagent red cells with known antigen specificity used to identify antibodies present in plasma

33
Q

How are the antigens present on red cells identified?

A

Test patient’s red cells using anti-A, B and D antisera = IgM reagents cause direct agglutination

34
Q

How are the antigens present in plasma identified?

A

Test patient’s plasma against reagent red cells of groups A and B

35
Q

How is a patient’s blood group defined?

A

By identifying the red cell and plasma antigens present

36
Q

How are antibodies screened for in blood?

A

Test patient’s plasma against several reagent red cells which express a known range of antigens

37
Q

What test is used to screen for antibodies in blood?

A

Indirect anti-globulin test = anti-human globulin added to plasma to facilitate red cell agglutination

38
Q

What does agglutination in the indirect anti-globulin test indicate?

A

Presence of an antibody

39
Q

How is blood selected for transfusion?

A

Blood is match, or compatible, with patient’s ABO and RhD group and donor cells are compatible with patient plasma

40
Q

How is the compatibility of donor cells with patient plasma checked?

A

By performing a cross match

41
Q

What occurs in an IAT crossmatch?

A

Patient plasma and anti-human globulin are added to donor cells = agglutination means donor cells are incompatible

42
Q

What are the indications for red cell transfusion?

A

Symptomatic anaemia = Hb <70g/l or <80g/l if cardiac disease
Major bleeding

43
Q

How are patients assessed during a red cell transfusion?

A

Transfuse single unit of red cells then reassess patient

44
Q

What are the indications for platelet transfusion?

A

Prophylaxis in bone marrow failure + very low platelets
Treatment of bleeding in thrombocytopenic patient
Surgery prophylaxis in thrombocytopenic patient

45
Q

What are the indications for FFP transfusion?

A

Treatment of bleeding in coagulopathy ( PT ratio >1.5)
Surgery prophylaxis in coagulopathy (PT ratio >1.5)
Management of massive haemorrhage

46
Q

How should FFP transfusions be used?

A

Transfuse early in trauma

Never use in absence of bleeding or planned procedure

47
Q

How must blood sample labels be filled in?

A

Fill in at bedside and must be done correctly with no corrections

48
Q

When are observations taken during a transfusion?

A

Before blood is commenced, at 15 minutes into transfusion and within 60 minutes of completion

49
Q

What is the full transfusion procedure?

A

Request - sample - sample receipt - testing - component selection - labelling - collection - prescription - administration

50
Q

What steps of the transfusion procedure take place in the lab?

A

Sample receipt - testing - component selection - labelling

Haematology (24 decks)

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