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Kat's Pathology > Blood Transfusions 1 > Flashcards

Blood Transfusions 1 Flashcards

1
Q

What determines ABO blood groups (2)

A

Antigens on the red cell membrane (these antigens are sugars)
The naturally-occuring antibodies in the plasma (these antibodies are IgM)

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2
Q

What does ABO incompatible blood transfusion cause

A

Massive intravascular haemolysis - potentially fatal

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3
Q

Group A antibodies present

A

Anti-B

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4
Q

Group B antibodies present

A

Anti-A

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5
Q

Group AB antibodies present

A

None

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6
Q

Group O antibodies present

A

Anti-A and Anti-B

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7
Q

Group A antigens present

A

A antigen

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8
Q

Group B antigens present

A

Group B

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9
Q

Group AB antigens present

A

A and B antigens

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10
Q

Group O antigens present

A

None

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11
Q

Red cells which carry the RhD antigen

A

RhD positive

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12
Q

What do RhD negative patients lack

A

RhD antigen

These patients make immune anti-D if exposed to RhD positive red cells
Immune anti-D antibodies are IgG, which do not cause direct agglutination of RBCs - no immediate haemolysis and death, but delayed haemolytic transfusion reaction

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13
Q

Who can get RhD negative blood

A

Anyone

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14
Q

What can occur if RhD positive blood is given to a RhD negative patient

A

Form anti-D - RhD negative blood would be an issue in any future transfusions

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15
Q

Why is RhD antigen relevant

A

Immune Anti-D made by a Rh negative mother exposed to Rh positive blood, can cause haemolytic disease of the newborn or severe fetal anaemia and heart-failure (hydrops fetalis) in RhD-negative females of child bearing potential.

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16
Q

What percentage of the population are RhD positive

A

85% are RhD positive

15% are RhD negative

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17
Q

What is tested before transfusion (2)

A

ABO and RhD group

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18
Q

What Ig are immune antibodies

A

IgG

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19
Q

How many RBC antigens are there

A

100s, but the most important are A, B and D

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20
Q

How are RBC antibodies created (2)

A

As a result of transfusion and/or pregnancy

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21
Q

Why must we identify clinically significant RBC antibodies and transfuse RBCs that are negative for that antigen

A

To prevent a delayed haemolytic transfusion reaction

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22
Q

Where does a delayed haemolytic transfusion reaction occur

A

Spleen

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23
Q

Where are RBC antigens present

A

Expressed on RBC membrane

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24
Q

How are patients plasmas screen for IgG antibodies

A

By mixing with 2 or 3 reagent cells that, between them, express all the important red cell antigens. These reagent red cells are blood group O.

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25
Q

What technique is used for antibody screening for plasma

A

Indirect antiglobulin technique

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26
Q

What is IAT (indirect antiglobulin technique)

A

Low ionic strength saline brings the cells closer together and the mixture is incubated at 37 degrees.

Bridges red cells coated by IgG which cannot themselves bridge 2 red cells - to form a visible clump - takes 30mins incubation at 37 degrees.

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27
Q

When is an antibody screen done

A

Before every transfusion, even if it has been done before

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28
Q

What is G&S

A

Group and Screen

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29
Q

What will happen if there is an immune antibody during the antibody screen

A

The red cells will clump - positive screen.

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30
Q

How is blood grouping and antibody screening automated (6)

A

Bar coded samples (id correct throughout – no mix up)
Computer interfaces
Robotic sample and reagent handling
Liquid level sensors (? failed to add reagent)
Reading of results by image analysis
Interpretation of results
Download to patient record

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31
Q

Why is automation of blood grouping and antibody screen good

A

No manual steps = safer and quicker

32
Q

What cell panels are used to identify RBC antibodies

A

10 cell panel

33
Q

What is donor blood labelled with (4)

A

ABO and D type

Other Rh antigens and K

34
Q

Who is given K negative blood for transfusion

A

Females of childbearing potential

35
Q

What is HDFN

A

Haemolytic disease of the foetus and newborn

36
Q

Why is it important to given females of childbearing age K negative blood

A

Anti-K can cause haemolytic disease of the newborn

37
Q

What proportion of the population is K negative

A

85-90%

38
Q

What is the next step after ABO and Rh status is matched

A

Serological crossmatch

39
Q

What is the serological cross match for

A

Detects any antibody:antigen reactions between the donor and recipient blood

40
Q

What are the two forms of serological crossmatch and what is involved in each.

A

Full crossmatch - indirect antiglobulin technique. Patient plasma is incubated for 30-40 mins, will pick up antibody antigen reaction that could cause destruction of the red cells and cause extravascular haemolysis
Add antiglobin reagent.

Immediate spin (saline, room temperature) - incubate patient plasma and donor red cells for 5 mins only and spin, will detect ABO incompatibility only

41
Q

What are the drawbacks of immediate spin for serological testing

A

Will only detect ABO incompatibility and used in an emergency to detect if the right ABO group has been selected.

This prevents an immediate, but not delayed haemolytic transfusion reaction.

42
Q

What is electronic crossmatching of blood

A

If we have tested the patient’s blood group twice (and it is the same) and the recent antibody screen is negative we can select blood without doing any mixing.

43
Q

What are the benefits of electronic crossmatching of blood (5)

A

This only takes a few minutes
There has to be a computer algorithm in place and it should be set up to prevent incompatible blood being issued
Blood is only issued when it is needed and it is quicker. It also means that all the blood is in the stock fridge, not assigned to a patient. We can even release blood from a fridge on another site – this is called remote issue.

44
Q

When might electronic crossmatching be unsuitable (3)

A

Some patients are not suitable for electronic crossmatching – those with anomalous blood groups, those with red cell antibodies and those who have only had a blood group tested once.

45
Q

What approach is used in clinical transfusion practice

A

Patient blood management is the modern approach to clinical transfusion practice.
You should remember this whenever you consider whether transfusion is needed.
It is the same as any other treatment decision. And must involve the patient.

46
Q

What needs to be considered when deciding whether a patient needs a blood transfusion (6)

A 
Is the patient bleeding? 
What are the blood results? 
Is the patient symptomatic? 
Will a transfusion solve the problem? 
What are the risks of transfusion? 
Are there alternative treatments?
47
Q

What is the importance of patient consent with blood transfusions (4)

A

‘Valid’ consent is required for transfusion (verbal)#
Alternatives should be offered if appropriate
If transfused in an emergency, patient must be informed afterwards
Involve patients in the process to ensure they get the right blood and the right ‘special requirements’

48
Q

What is the lifespan of red cells for transfusion (3)

A

Stored at 4 degrees for 35 days.
Must be transfused within 4 hours of leaving fridge
Transfer 1 unit RBC over 2-3 hours

49
Q

What is the lifespan of platelets for transfusion (2)

A

Stored at 22 degrees for 7 days

Transfuse 1 unit of platelets over 20-30 minutes

50
Q

What is the lifespan of plasma for transfusion (2)

A

No need to crossmatch, but does need 30-40mins to thaw

Transfuse 1 unit over 20-30 mins.

51
Q

What warrants RBC transfusions (4)

A

Major blood loss - if >30% blood volume lost
Per-op, critical care - Hb <70g/L versus 80g/L
Post chemo: Hb<80g/L
Symptomatic anaemia - ischaemic heart disease, breathlessness, ECG changes

52
Q

How often should the Hb be checked when transfusing RBCs

A

Pre transfusion and after every 1-2 units

Transfusion to above 100g/L is rarely required, unless symptomatic or severe cardiac/respiratory disease, etc…

53
Q

What effect does 1 unit of RBC have on Hb

A

1 unit RBC gives a Hb increment of 10g/L in a 70-80kg patient

54
Q

What is the maximum surgical blood ordering schedule (MSBOS)

A

Red cells often allocated to a patient but, if not used, are taken
back into stock…repeatedly, may expire.
So, MSBOS is based on negotiation between surgeons and
transfusion lab about predictable blood loss for ‘routine’ planned
Surgery.
Some operations rarely need blood - eg: gall bladder op
Some operations always need blood – eg: aortic aneurysm repair
Junior doctors / nurses doing pre-admission clinics have some idea
what is normal. Have to be flexible if non-standard surgery or
special patient requirements (eg: bleeding disorder)

55
Q

What steps are required RE blood preparation pre elective procedures (2)

A

Group and Screen (and save) - then if no antibodies present, do not cross-match blood, but just save sample in the fridge (if unexpected need for blood, can provide it within 10mins (by electronic issue, as no anti bodies present)

Always crossmatch up front if RBC antibodies are present

56
Q

How is a patients own blood used during surgery (3)

A

Cannot use pre-operative autologous deposit (i.e. donate own blood before operation)

Intra-operative cell salvage - collect blood lost during surgery, centrifuge, filter, wash and re-infuse it. Used in most surgical and obstetrics units
Post-operative cell salvage - collect blood lost post-op into wound drain, filter and re-infuse. mainly used in orthopaedic surgery (i.e. knee)

57
Q

What is in cell salvage blood

A

All coagulation factors and platelets are removed

58
Q

Autologous

A

Own

59
Q

Allogeneic

A

Donor

60
Q

When is CMV negative blood required

A

Only required for intra-uterine and neonatal transfusions (new guidance 2012). Also for elective transfusion in pregnant women (baby in-utero is exposed to maternal transfusion)

61
Q

What are some special requirements for blood transfusion (3)

A

CMV negative
Irradiated blood
Washed

62
Q

When is irradiated blood required for transfusion

A

Required for highly immunosupressed patients, who cannot destroy incoming donor lymphocytes: which can cause (fatal) transfusion associated graft versus host disease (TA-GvHD)

63
Q

When is washed blood required for transfusion

A

Red cells and platelets are only given to patients who have severe allergic reactions to some donors’ plasma proteins

64
Q

When is platelet transfusion contra-indicated (2)

A

Platelet transfusion is contraindicated in heparin-induced thrombocytopenia (HIT) and TTP (can worsen)

65
Q

By how much does 1 unit of platelets raise platelet count

A

30-40 x 10^9/L

66
Q

What is the indication for a massive platelet transfusion

A

Aim for platelets >75 x 10^9/L

67
Q

When are platelets transfused post-chemo

A

If <10x 10^9/L (or <20 if sepsis)

68
Q

When are platelets transfused to prevent surgical bleeding

A

<50 x 10^9/L (of <100 if critical site such as CNS or eyes)

69
Q

When are platelets indicated in platelet dysfunction or immune causes

A

Only if there is active bleeding

70
Q

What is FFP

A

Fresh frozen plasma containing all clotting factors

71
Q

What is the adult dose of FFP

A

15mL/kg

1 unit FFP contails 250ml = adult dose is 4-6 un its.

72
Q

What is the treatment of choice to reverse warfarin

A

PCC (prothrombin complex concentrate)

73
Q

When is platelet transfusion indicated (4)

A

Massive transfusion
Prevent bleeding post-chemo
Prevent bleeding - surgery
Platelet dysfunction or immune cause

74
Q

What are the FFP transfusion indications (4)

A

Massive transfusion
Disseminated intravascular coagulopathy (DIC)
Liver disease and risk
Rarely for coagulation factor replacement where factor concentrate not available

75
Q

When is a massive FFP transfusion indicated

A

Blood loss >150ml/min

76
Q

When should you give FFP in DIC

A

WITH active bleeding

77
Q

When should you give FFP in liver disease

A

PT ratio >1.5 x normal

Kat's Pathology (105 decks)

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