Blood Transfusion

Question 1

why transfuse blood?

Answer 1

Low levels of blood:

• Mainly because of bleeding
• But also failure of production
• (excess rate of destruction)

Question 2

where do blood gorups arise from?

Answer 2

Arise from antigens (on surface of red cells)

= something that provokes an immune response

Question 3

blood groups:

Red cell antigens are expressed where?

Answer 3

on cell surface (proteins, sugars, lipids)

Question 4

blood groups can provoke what?

Answer 4

SCan provoke antibodies (if of different blood group from someone and get transfused or exposed to red cells of someone else)

Question 5

what are the different ABO phenotypes?

Answer 5

ABO on surface of red cells

Question 6

ABO Blood Group Antigens - what are they?

Answer 6

ABO gene encodes glycosyltransferase

Glycans added to proteins or lipids on Red Cells

A and B genes code for transferase enzymes

A antigen is N-acetyl-galactosamine

B antigen is galactose

‘O’ gene is non-functional allele

So A and B are (co-)dominant and O is recessive

A and B code for different transferase

O doesn’t put anything on

Question 7

If blood group A, have antibodies against….

Answer 7

B

Question 8

If blood group B, have antibodies against….

Answer 8

A

Question 9

If blood group O, have antibodies against….

Answer 9

A and B

Question 10

If blood group AB, have no antibodies against….

Answer 10

A and B

Question 11

what is Immune tolerance?

Answer 11

Self vs non-self

Body will develop tolerance and delete anything active against bodies own tissues unless you develop autoimmunity

Usually most antigens will only develop antibody against it if you develop it later in life

Question 12

IgM: anti-A/B naturally occurring

can it fix complement?

Answer 12

IgM can fix complement, therefore if your blood group A and come across B then it is a violent reaction because of the fixation of complement

Question 13

what is the thermal range of IgM

Answer 13

IgM antibodies only normally react at cold temperatures but ABO antigens go up to 37 degrees which is why you get such catastrophic reactions

Question 14

how common is each blood group?

Answer 14

Varies geographically:

• A 42%
• B 9%
• AB 3%
• O 46%

Question 15

what is the Red Cell Donor/Recipient Compatibility?

Answer 15

can give patient the same blood group as to what they are e.g. if patient is A then you can give them A blood

If donor is O then the blood doesn’t contain any A or B for the patient antibodies to react against. O are therefore called universal donors, can be transfused into anyone

AB are tolerant to both A and B antigen and can receive blood groups form any type

Question 16

what is the FFP (fresh frozen plasma) Donor/Recipient Compatibility?

Answer 16

Reverse is true for plasma (comapred to red cells)

Plasma contains antibodies

If patient is A then they will have A antigen on the surface of their red cells and the donor is B and therefore will have anti A in their plasma and you can get a reaction

Often a reverse to that of red cells

Reactions for plasma are much less severe than red cells

Can usually get away with crossing blood groups in plasma

Question 17

RhD blood group system

Answer 17

Each group can be either RhD positive or RhD negative, which means in total there are 8 blood groups.

Protein antigen

Very immunogenic protein

DD – positive for the RHD gene

dd – negative for the RHD gene

Question 18

what is Anti-RhD?

Answer 18

RhD negative individuals can make anti-D if exposed to RhD+ cells

(only in) Transfusion or pregnancy

Anti-D can cause transfusion reactions or haemolytic disease of the newborn

Question 19

what information is required form blood donors?

Answer 19

• Extensive ‘behavioural’ screening
• Sex, age, travel, tattoos…………
• Tested for ABO and Rh blood groups
• Screened for HepB/C/E, HIV, syphilis
• Variably screened for (if you travelled somewhere): HTLV1, malaria, West Nile virus, Zika virus…

Question 20

what is Apheresis donors?

Answer 20

Apheresis is a medical procedure that involves removing whole blood from a donor or patient and separating the blood into individual components so that one particular component can be removed. The remaining blood components then are re-introduced back into the bloodstream of the patient or donor

Question 21

what are the blood components and products?

Answer 21

Blood in processing centres is separated out in these 3 sections

Question 22

what are the Indications for red cell transfusion?

Answer 22

1. To correct severe acute anaemia, which might otherwise cause organ damage (Someone that is bleeding, road traffic accident or operation)
2. To improve quality of life in patient with otherwise uncorrectable anaemia
3. To prepare a patient for surgery or speed up recovery
4. To reverse damage caused by patient’s own red cells - Sickle Cell Disease

Question 23

how are RBCs stored and used?

Answer 23

Stored at 4oC

Transfuse over 2-4 hours

1 unit increments ~5 g/L

Question 24

how are platelets stored and used?

Answer 24

•1 dose platelets (=4 pooled or 1 apheresis donor) - 1 dose is from 4 donations

• increments 20-40.109/L
• Stored at ~22oC, shelf life 7 days
• Transfuse over 20-30 minutes

Room temp and short shelf life

Question 25

what are the uses of platelets?

Answer 25

• Massive haemorrhage - Keep platelet count above 75x109/l
• Bone marrow failure - platelet count <10-15 × 109/litre, or <20 × 109/litre if additional risk, e.g. sepsis
• Prophylaxis for surgery - Minor procedures 50x109/l;, More major surgery 80x109/l; CNS or eye surgery 100x109/l
• Cardiopulmonary bypass - use only if bleeding

Question 26

whata re the plasma ocmponents - how is it stored an used?

Answer 26

1 unit from 1 unit of blood

Stored frozen, allow 30 minutes to thaw

1 unit of FFP for 1 bag of red cells

Question 27

what are the indicationsf or fresh froen plasma?

Answer 27

massive haemorrhage (use in 1:1 ratio?)

DIC with bleeding

‘prophylactic’ (if expected to bleed)

Question 28

what is crypoprecipitate?

Answer 28

Cryoprecipitate, also called cryo for short, is a frozen blood product prepared from blood plasma. To create cryoprecipitate, fresh frozen plasma thawed to 1–6 °C is then centrifuged and the precipitate is collected.

1-2 pools if fib <1.0g/dl (1.5g/dl)

Stored frozen; allow 20 minutes to thaw

Cryoprecipitate – prescribe less, made from gradually thawing FFP, fibrinogen concentrate

Question 29

choosing ocmpatibel blood - Dealing with Blood Bank

how is it done?

Answer 29

Blood sample (EDTA)

Two sample policy (need to samples to avoid ABO mistakes)

Group and Screen/Save

Cross matching

Question 30

what is ‘Group and Screening’?

Answer 30

(Lab check) ABO and RhD type

Checked against historical records

Screen for allo-antibodies in serum

If patient is A, if you add anti-A monoclonal antibodies to them the red cells clump together meaning there is A antigen on surface of red cells

If you add B as seen in the next column, red cells still dispersed and no reaction

In anti-AB you see the red cells are all clumped together

You also do a reverse group where you add the patients serum to the cells

When you add the serum form that patient to A cells, it doesn’t contain anti-A and there is no agglutination

But when you add the patients serum to B cells the patient does have anti-B and there is agglutination

Question 31

what is Coombs Test?

Answer 31

Trying to detect antibodies on the surface of red cells

Blood grouping is IgM antibodies – they are multivalent

If IgG on surface of red cells then they wont clump together

Because it is bivalent it will link the red cells together and cause a agglutination so the test can pick up IgG on the surface of red cells

Positive = antibody on surface of red cells

Question 32

Coombs Test – what is direct vs indirect?

Answer 32

Direct:

• autoimmune haemolytic anaemia
• passive anti-D
• haemolytic transfusion reactions

Indirect:

• Cross matching

Indirect coombs test = when you are adding an external antibody to see it binds the red cells which you then cross link and we use this in cross matching

Question 33

what is Antibody Screening?

Answer 33

Finally we screen sample you sent in blood bank for alloantibodies

They are quite rare

If reaction, like in this case, against cells 1, 2, 3 and 8 then you can say this patient has an anti-D and you should choose D negative cells to transfuse

Question 34

whhat is the process of Development of maternal Anti D antibodies (sensitisation)?

Answer 34

Mother can develop antibodies against foreign antigens that are carried by their babies that have been encoded by paternal alleles

RHD system is the most important

15% of mothers are RDH- and if the father is RDH+ which most men are, then they are at risk of developing the disease

If red cells leak across the placenta in pregnancy or particularly at birth then the mother will pick up the foreign cells and form an antibody

It’s a protein and usually an IgG and IgG crosses the placenta

The IgG in subsequent pregnancies can cross the placenta and cause alloimmune haemolysis in the baby, the baby then become anaemic and can get cardiac failure and die

Question 35

what is anti D?

Answer 35

Anti-D immunoglobulin after birth

The injection will destroy any RhD positive blood cells that may have crossed over into your bloodstream during the delivery. This means your blood won’t have a chance to produce antibodies and will significantly decrease the risk of your next baby having rhesus disease.

Question 36

how is RhD delt with in pregnancy?

Answer 36

All RhD mother are screened throughout pregnancy for the development of antiD

At around 28 weeks of pregnancy of pregnancy, all RhD negative mothers are injected with antiD so in the latter stages of pregnancy there is less chances of developing antiD subsequently and likewise at birth every mother should be picked up that is RhD negative and if they have a RhD positive baby they should have further antiD to prevent problems in future pregnancies

Question 37

Haemolytic disease of the newborn (HDN) - how do you prevent it and how do you treat it?

Answer 37

Prevention using prophylactic anti-D:

• Sensitising events
• Routine at 28/40

Treatment by careful monitoring:

• Antibody titres
• Doppler ultrasound
• Intrauterine transfusions

Neonatal alloimmune thrombocytopenia (NAIT) similar process for platelets - If baby born with low platelet count at birth, one of the first things to think about is there is an antibody present that we can pick up on our tests​