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Haematology > Week 1- blood transfusion > Flashcards

Week 1- blood transfusion Flashcards

1
Q

What are the main blood groups?

A

ABO- this can be A, B, AB or O

Rh(D) - can be positive or negative

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2
Q

What can a transfusion service supply?

A

Blood components- red cells, platelets, plasma, cryoprecipitate
Blood products- albumin, IV immunoglobulin, normal immunoglobulin, specific immunoglobulins, anti-D immunoglobulin, prothrombin complex concentrates.

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3
Q

What is the difference between blood components and blood products?

A

Blood components are made by centrifuging blood to split it into its components- red cells, Buffy coat and plasma. Blood components are from one donor whereas blood products can be from up to 20000 donors put together.

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4
Q

How would you go about identifying a blood component?

A

Quote the component label (e.g. red cells in additive solution) and the donation number.

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5
Q

How many blood donations do you need to make one standard dose of platelets?

A

You need 4 adult donors to make 1 unit of platelets.

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6
Q

If you give a patient blood products, how many donors are you exposing that patient too?

A

Thousands of donors.

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7
Q

What must a donor be checked for before giving blood?

A

Any signs of infection- e.g. sore throat, diarrhoea etc
Any risk of foreign infection e.g. malaria- recent travel to a foreign country
Exclude risk of transmitting disease e.g. neurological conditions such as MS, malignancy
Test the blood for HIV, Hepatitis, HCV, HBV, syphilis etc.

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8
Q

What is already in the bag before the blood is donated?

A

A measured unit of anticoagulant. This is why you need exactly 465mls of blood- to match the amount of anticoagulant present.

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9
Q

What occurs after the blood has been donated to it?

A

It gets centrifuged to split it into its components.

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10
Q

What occurs to the red cells to deplete them of their excess white cells after centrifusion?

A

They are run through a leucodepletion filter.

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11
Q

What temperature are red cells stored at?

A

4 degrees +/- 2

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12
Q

What temperature is plasma stored at?

A

-30 degrees (fresh frozen plasma- can be stored for up to 3 years)

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13
Q

What temperature are platelets stored at?

A

22 degrees with continual agitation.

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14
Q

What should happen to red cells that are removed from storage for more than 30 minutes?

A

They either need to be transfused within 4 hours or returned to the blood transfusion lab. They cannot be stored back in the fridge.

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15
Q

What is the window of time that you can transfuse the platelets within once removed from their environment?

A

1 hour.

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16
Q

What antigens does blood group A have on its surface?

A

A antigens

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17
Q

What antigens does blood group B have on its surface?

A

B antigens

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18
Q

What antigens does blood group AB have on its surface?

A

Both A and B antigens

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19
Q

What antigens does blood group O have on its surface?

A

Neither A nor B antigens.

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20
Q

What antibodies will someone with blood type A create?

A

Anti-B antibodies

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21
Q

What antibodies will someone with blood type B create?

A

Anti-A antibodies

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22
Q

What antibodies will someone with blood type AB create?

A

None.

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23
Q

What antibodies will someone with blood type O create?

A

Both antibodies for A and B because it recognises both as foreign.

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24
Q

What is the reaction called if you wrongly transfuse the wrong blood type into a patient?

A

Haemolytic reaction.

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25
Q

Why is group O called the universal donor?

A

Because they haven’t got any antigens on their cell surface meaning no reaction will occur.

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26
Q

What type of antibodies are anti A and anti B? What is the significance of this?

A

IgM

They are good at activating complement leading to red cell destruction.

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27
Q

What do the A and B genes code for?

A

A specific transferase enzyme which adds a sugar residue to a precursor H substance on the red cell membrane.

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28
Q

What are the dominant blood types in the ABO grouping?

A

A and B are both dominant over O.

A and B are co-dominent.

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29
Q

Where are the genes that determine our ABO blood group found?

A

On chromosome 9.

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30
Q

In order to inherit blood type O, you need to inherit one O from both parents. True or false?

A

True.

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31
Q

What does the presence of Rh(D) antigen on the RBC surface determine?

A

Whether you are Rh(D) positive (have the antigen) or negative (don’t have the antigen)

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32
Q

What are the majority of the population in regards to Rh(D) positive or negative?

A

85% are Rh (D) positive.

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33
Q

Do any bacteria carry a substance that resembles RhD?

A

No.

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34
Q

What happens if you are RhD negative and are exposed to RhD positive RBCs?

A

You will develop antibodies against the RhD antigen. Called anti-D

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35
Q

How do you determine a patients blood group (what is the phenomenon known as?)

A

Agglutination phenomenon.

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36
Q

Why don’t we give all the population who need blood O blood?

A

Only 47% of the population have O blood so we would run out.

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37
Q

Describe how agglutination works?

A

If you add a known antibody to a red cell sample, e.g. known anti-A antibody, if the blood type contains A it will agglutinate (group together and form a clump). If it doesn’t contain A, there will be no agglutination.

38
Q

What occurs if you add anti-A antibody to group B blood cells?

A

No agglutination occurs.

39
Q

What occurs if you add anti-A antibody to group AB blood cells?

A

Agglutination will occur because the A antigen is present (along with a B antigen).

40
Q

What occurs if you add anti-A antibody or anti-B antibody to group O cells?

A

Nothing occurs because neither antigen is present.

41
Q

How do we obtain anti-A antibodies and anti-B antibodies that are used for agglutination?

A

Used to be from plasma however now manufactured using hibridoma cell lines.

42
Q

When there is no agglutination to both anti-A antibody, anti-B antibody and anti-AB antibody, the blood type must be O. How would you check this?

A

You take known A red cells and known B red cells and add it to the patients plasma. Now you should get agglutination because the plasma will attack the foreign blood types.

43
Q

What is the process for obtaining a blood sample for crossmatch?

A 
Ask the patient their name and DOB
Check this is the correct patient
Complete request form
Once sample is taken, ask patient their details again and fill in the side of the bottle (no stickers)
Send sample and form to transfusion lab
Prepare patient for transfusion
44
Q

What occurs at the transfusion lab once they receive a sample?

A

Sample is centrifuged to split into components.

45
Q

What occurs at the transfusion lab once they receive a sample?

A

Sample is centrifuged to split into components.
ABO and Rh(D) group are determined.
Screen for irregular red cell antibodies

46
Q

On a blood report, what does + denote and what does 0 denote?

A

+ denotes agglutination

0 denotes no agglutination

47
Q

When would you screen for irregular antibodies?

A

These are not naturally occurring so only will come if they have had previous exposure e.g. previous transfusion or pregnancy.

48
Q

What type of antibodies are irregular antibodies?

A

IgG

Therefore they don’t agglutinate.

49
Q

What type of antibodies are irregular antibodies?

A

IgG

50
Q

What type of testing is used for irregular antibodies?

What is this technique called?

A

Agglutination testing again. You use O red cells from three donors that between them have all the types of the red cell antigens present. you then add the patients plasma to them to see if agglutination occurs. However agglutination on these antibodies doesn’t cause cross linking (because they are IgG), therefore you need something that binds the antibodies together to make it visible (anti-human immunoglobulin).
Called indirect anti globulin test

51
Q

Once the units have been issued to the blood fridge, if thy are not required for the patient, what happens to them?

A

If not used within 24 hours, they are returned to the transfusion laboratory.

52
Q

How many units should be retrieved from the fridge at any one time?

A

1 unit at a time.

53
Q

What do nursing staff have to check for before giving the blood transfusion?

A

Check integrity of the bag- look for clots, gas bubbles, haemolysis etc.
Check expiry date
Check patient details.
Must record pre-transfusion obs before hand.

54
Q

What are the indications for carrying out a red cell transfusion?

A

Anaemia- however look at Hb level AND symptoms. Some patients may function on 90g/L of haemoglobin quite normally, however others may have serious symptoms. Consider if the diagnosis is secure? Is there an alternative to red cell transfusion? Is red cell transfusion justified?

Acute blood loss

55
Q

What symptoms will you get with acute blood loss? Describe 10%, 20%, 30%, >30% and >50%.

A

10%- asymptomatic
20%- tachycardia, postural hypotension, weak, thirsty
30%- These can be tolerated if fit
>30%- confusion, restlessness, oliguria, coma
>50%- Prompt resus is mandatory.

56
Q

What is the normal circulating blood volume?

A

70ml/kg

57
Q

What is the body’s physiological response to losing blood?

A

Increased HR and contractile force
Vasoconstriction
Protection of brain, heart and adrenal cortex
Pulmonary hyperventilation
Fluid shift from ECF to intravascular space
Renal conservation of sodium and water.

58
Q

How would you approach acute blood loss?

A

1- Arrest bleeding
2- gain IV access
3-Send samples for cross-matching
4-Restore and maintain blood volume using saline, albumin, gelofusin
5-ABO and Rh(D) with irregular antibody screening takes 1 hour.
ABO and Rh(D) screening- 20 mins
Emergency O group- immediately available
6- aim to maintain normal pulse rate, BP, consciousness, urine output >30ml/hr, hb>100g/L

59
Q

What temperature are platelets stored at?

A

22 degrees Celsius

60
Q

Do you need to crossmatch platelets?

A

No crossmatch procedure is required, however need to take into account the patients ABO and Rh(D) groups.

61
Q

How many donors make up one unit of platelets?

A

4 donors mixed together form one unit of platelets.

However there is a technique where you have a single donors platelets- using a cell separator machine.

62
Q

In what situations is a platelet transfusion indicated?

A

Low platelet count (5-10x 10^9) normal is (150-400x10^9)
However if the patient has a fever, prophylactic platelet transfusion is given at a higher threshold (20-30)
Symptoms of bleeding
congenital platelet functional defects (thrombocytopenia)

63
Q

What temperature is fresh frozen plasma stored at?

A

-30 degrees celsius.

64
Q

How long can you store fresh frozen plasma for?

A

3 years.

65
Q

Once it has been removed from the fridge, how long do you have to use it?

A

4 hours from it being thawed.

66
Q

What are the indications for fresh frozen plasma?

A

Bleeding or surgery in liver disease with impaired coagulation.
Coagulopathy following massive transfusion- the plasma becomes diluted so much.
Disseminated intravascular coagulation (small blood clots form throughout the bloodstream- depleting platelets and clotting factors.

67
Q

What would occur if Group A blood was transfused into a group O patient? What is this reaction called?

A

The group A blood would bind with the anti-A antibodies in the group O blood. This activates complement
Immediate haemolytic transfusion reaction.

68
Q

What does complement activation cause on the red cell membrane of incompatible blood cells?

A

Results immediately in rupture of the membrane. Disrupted red cells release thromboplastins that indiscriminately activate the complement cascade. Some of the activated complement components act on blood vessels to cause leakage and dilatation, so fluid begins to leak out of the vessels, decreasing bp (also because of dilatation the bp drops further).

69
Q

Which complement components are activated? What is their function?

A

C3a and C5a.
They increase vascular permeability and dilate blood vessels.
Cause the release of serotonin and histamine- which cause fever, chills, hypotension and shock.
Formation of the membrane attack complex leads to rupture of the red blood cells.

70
Q

What occurs in the coagulation pathway in an immediate heamolytic transfusion reaction?

A

Thromboplastic material from haemolysed red cells leads to indiscriminate activation of the coagulation system. Causing disseminated intravascular coagulation.

71
Q

What activates the Kinin system?

A

Activated factor VII

72
Q

What occurs in the kinin system in an immediate haemolytic transfusion reaction?

A

Formation of bradykinin- causes arteriolar dilatation and increased vascular permeability.
This leads to hypotension which in turn leads to the release of catecholamines- leading to vasoconstriction within the kidneys and other organs.

73
Q

NET effect of all three systems (kinin, complement and coagulation) on patients?

A

Leads to systemic hypotension, disseminated intravascular coagulation, renal vasoconstriction, formation of renal intravascular thrombi, shock, renal failure.
Often it is fatal.

74
Q

What symptoms will a patient with immediate haemolytic transfusion reaction have?

A 
Pyrexia/rigors
Faintness/dizziness
Tachycardia/tachyopneoa/hypotension
Pallor/sweating
Headaches/chest or lumbar pain
Local pain at infusion site
Cyanosis
75
Q

How much blood needs to be transferred for it to occur?

A

Could occur with just 1ml of blood transferred

76
Q

What do you do if an immediate haemolytic reaction is occurring?

A

Stop the transfusion
Give IV fluids to maintain BP and urine output
Obtain blood samples for- transfusion lab, FBC and blood film, coagulation screen, biochemistry, blood cultures, serum haptoglobin.
DO NOT REMOVE THE CANNULA FROM THE PATIENTS VEIN.

77
Q

What does the transfusion lab do on the samples given after/during an immediate haemolytic transfusion reaction?

A

They test pre transfusion and post transfusion samples for the ABO grouping and Rh (D) grouping. They also test it on transfused and untransfused units.
Direct anti-globulin test on pre and post transfused samples
Determine whether or not the units are compatible
Bacteriological culture on remains.

78
Q

What is a delayed haemolytic transfusion reaction?

A

Haemolysis occurs 5-10 days after transfusion.

79
Q

How does a delayed haemolytic transfusion reaction present?

A

Symptoms variable, however similar to IHTR but less acute.
Unexplained fall in Hb as transfused red cells are destroyed
Appearance of jaundice, renal failure or biochemical features associated with IHTR.
Detection of positive DAGT or irregular antibodies in post transfusion blood samples.

80
Q

What occurs in a delayed haemolytic transfusion reaction? In the example of someone being Kell negative being transfused with Kell positive blood?

A

The body produces anti-kell antibodies and forms complexes with the red blood cells. However complement is not activated (as is the case with most irregular antibodies), therefore there is no red cell destruction. However when the blood goes through the spleen, macrophages attack them resulting in red cell destruction. If some of them escape this, they go back into the circulation in the shape of a sphere (due to their membrane damage- called spherocytes). The Hb released from the damaged red cells is eventually metabolised to bilirubin, so the patient may be jaundiced.

81
Q

How would you test the blood for delayed haemolytic transfusion reactions?

A

Add anti-human globulin and it will result in agglutination.

82
Q

What will the lab results of someone with delayed haemolytic transfusion reaction look like?

A

Positive agglutination on addition. of anti-human globulin
Anaemia, spherocytic red cells on blood film
Elevated bilirubin and LDH

83
Q

Why does a febrile non-haemolytic transfusion reaction occur?

A

They occur either because the recipient has anti-HLA antibodies that bind to white cells or as a result of vasoactive and pyrogenic substances being released from the white cells in the blood during storage of blood components.

84
Q

How does a febrile non-haemolytic reaction present?

A

Rapid temperature rise of 1-2 degrees, chills, rigors
Antibodies to contaminating white cells
Release of cytokines and vasoactive substances during storage

85
Q

What would investigations into febrile non-haemolytic reaction show?

A

HLA antibodies

no evidence of red cell incompatibility.

86
Q

Who do febrile non-haemolytic reactions occur in?

A

Usually occur in people who get blood transfusions a lot.

87
Q

How can you stop febrile non-haemolytic reactions?

A

Prevent with anti-paretics (paracetamol)

Leucodepleting blood components.

88
Q

What is an urticarial reaction?

How does it present?

A

IgE and mast cell response to infused plasma proteins

Presents as a rash/weals within a few minutes of starting the transfusion.

89
Q

How do you stop an urticarial reaction?

A

Slow the transfusion

Consider anti-histamines.

90
Q

NOTE- be wary of circulatory overload.

A

Can cause pulmonary oedema. Problems can be avoided by reducing transfusion rate or by administering diuretics.

91
Q

What would transfusion of bacterial infection result in?

How would you respond?

A

A response similar to that of IHTR.
Immediate response should be exactly the same as in IHTR. Once the lab has confirmed your patient has not had an ABO transfusion reaction you can treat with broad spectrum antibiotics

Haematology (26 decks)

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