blood transfusions

Question 1

• What is the difference in the formation of antigens in group A, B and O?

Answer 1

O - H antigen (H stem only)

A - N-acetyl galactosamine (type of sugar residue) added to glycoprotein (fuc) of H stem

B - Galactose added to glycoprotein (fuc) of H stem

Question 2

• How does a mother being RhD negative affect the foetus during pregnancy?

Answer 2

If foetus is RhD positive, then the mother’s anti-D will cross placenta and attach to RhD positive red cells of foetus

Can cause haemolysis of foetal red cells

If severe: hydrops fetalis and death

If less severe: baby survives but after birth, high bilirubin levels can cause brain damage or death

Question 3

• What two things should be tested when trying to provide compatible blood for a patient needing a blood transfusion?

Answer 3

ABO and RhD blood groups on patient’s red cells

Antibody screen on patient's plasma

Question 4

• How does the compatibility testing before transfusing patients occur?

Answer 4

ABO group - test patient’s red cells with known anti-A and anti-B reagents

RhD group - test patient's red cells with known anti-D and reagent

Select donor blood of same ABO & RhD group

Antibody screen +/- antibody panel, to identify antibody(ies)

Cross match - patient's serum mixed with chosen donor red cells and if it agglutinates then they are incompatible

Question 5

• After centrifuging a unit of whole blood, what are the three components that are separated and how are these arranged?

Answer 5

Top - Plasma

Middle - Platelets

Bottom - Red Cells

Question 6

What does FFP contain?

what does transfusions of FFP treat?

how many units of FFP is obtained from one whole blood donor/ apheresis ?

Answer 6

FFP contains all the coagulation factors.

Transfusions of FFP are required for treatment of bleeding or to reduce the risk of bleeding in patients with coagulopathies (multiple clotting factor deficiencies resulting in prolonged PT, APTT or both).

1 unit of FFP is obtained from whole blood donation or by apheresis.
The standard adult dose of FFP 12-15mls/kg (each unit is approximately 270mls).

Question 7

what does cryoprecipitate contain?

what is it used to treat?

what treatment has replaced cryoprecipitate in treatment of patients with haemophilia A or VWF disease?

Answer 7

Cryoprecipitate contains fibrinogen, Factor VIII, von Willebrand factor and Factor XIII.

can be given to treat bleeding or to reduce the risk of bleeding when the fibrinogen level is low, which is usually as a result of major haemorrhage or disseminated intravascular coagulation

The availability of single factor concentrates for FVIII and VWF has replaced cryoprecipitate in the treatment of patients with haemophilia A and von Willebrand disease

Question 8

what are red blood cell transfusions used for?

how many units from whole blood donation?

how many units from apheresis?

Answer 8

Red cell transfusions are required to increase the haemoglobin and thus restore the oxygen carrying capacity of blood in patients with anaemia (low haemoglobin) or blood loss.

1 unit of packed red cells can be collected from a single whole blood donation. In some cases, an apheresis donor may be able to donate 2 units of packed red cells in one session.

Question 9

how much does a unit inc the haemoglobin conc by?

what is their shelf life and storage temperature?

Answer 9

1 unit of red cells usually results in an increase in the haemoglobin by 10g/L in an average adult (weighing 70kg).

Packed red cells have a shelf-life of 35 days and must be stored in a fridge at 4oC.

Question 10

what are platelet transfusions used for ?

what are the two methods to produce platelets?

Answer 10

Platelet transfusions are required for the treatment of bleeding or to reduce the risk of bleeding in patients with low platelet counts (thrombocytopenia) or platelet dysfunction (e.g. due to certain drugs such as antiplatelet medication)

There are 2 methods for producing platelets for transfusion:
1. Pooled platelets – this is where platelets separated from 4 whole blood donations are pooled together to make up 1 unit of platelets

2. Apheresis platelets – this is where a single donor donates 1 unit of platelets through apheresis



Question 11

what does one unit of platelets increase the platelet count by?

what should you check for post transfusion?

what is a platelets shelf life and temperature of storage?

Answer 11

1 unit of platelets usually results in an increase in the platelet count by more than 10 x 10^9/L. It is important to check for response to the transfusion both clinically, and by checking the platelet count post-transfusion.

Platelets have a shelf-life of 7 days only and are stored at room temperature ( 22oC). Platelets require constant agitation to ensure the platelets are continuously oxygenated within their gas permeable containers

Question 12

what are the plasma-derived medicinal products derived by fractionation from multiple plasma donations?

Answer 12

Human albumin solution
Immunoglobulins
Clotting factor concentrates

Question 13

what are the two types of antibodies against RBC antigens?

how is each one formed?

Answer 13

Naturally occurring

• IgM antibodies
• Their production is stimulated when the immune system encounters the ‘missing’ ABO blood group in foods or in microorganisms.

Acquired alloantibodies

• IgG antibodies.
• formed as a result of active immunisation (alloimmunisation) to ‘non-self’ RBC antigens following exposure to RBCs from another individual.

Question 14

What kind of haemolytic transfusion reactions can IgM and IgG antibodies result in?

Answer 14

• IgM ABO antibodies can cause acute HTRs through activation of the complement system resulting in massive intravascular haemolysis. However, they cannot cross the placenta to cause HDFN
• IgG antibodies generally do not cause massive intravascular haemolysis and death but do still cause haemolysis (mainly extravascular) resulting in delayed HTRs. IgG antibodies are also able to cross the placenta and cause HDFN.

Question 15

How come IgG ABO antibodies can cross the placenta but it does not usually cause HDFN?

Answer 15

Fetal red cells have poorly developed ABO antigens which are unable to support binding of the IgG antibodies

ABO antigens are found on numerous other cells (not just red cells) so any IgG ABO antibodies that have crossed the placenta can be ‘mopped-up’ by these cells

The rare cases of ABO HDFN usually occur in mothers who have especially high levels (‘high-titre’) of IgG anti-A and anti-B antibodies.
Any maternal IgG anti-A or anti-B antibodies present at birth in a baby’s plasma will disappear within a few months as the baby starts to develop their own IgM anti-A and anti-B antibodies

Question 16

what is the purpose of antibody screening?

Answer 16

to detect the presence of any acquired alloantibodies the patient may have developed.

The patient’s serum is tested against panels of RBCs which together are known to express all of the clinically relevant RBC antigens.

if there is an interaction between an antibody(ies) in the patient’s serum and an antigen(s) on the RBCs, agglutination will occur (i.e. antibody screen positive).

requires the addition of another reagent (anti-human globulin) before it can be seen.

Question 17

What are the uses of human albumin solution

Answer 17

replace plasma volume loss eg due to burns or trauma

induce dialysis in patients with low albumin level eg kidney or liver failure

replace plasma in plasma exchange eg treating autoimmune disorders

Question 18

what is the use of immunoglobulins

what are the two types used

Answer 18

provide passive immunity

normal immunoglobin- antibodies to common virus eg hep as measles or rubella

specific donors- from donors with a specifically high level of antibodies for a certain pathogen eg tetanus and hep B

Question 19

what are examples of single clotting factor concentrates

Answer 19

factor 8
factor 9
PCCs- prothrombin complex concentrates - factors 2, 7, 9, 10 (essentially the vitamin K factors)
fibrinogen concentrates

Question 20

what are factor 8 and 9 concentrates used for

Answer 20

haemophilia A (factor 8 deficiency)

Haemophilia B (factor 9 deficiency)

Question 21

what are PCCs used for

Answer 21

used to reverse the effect of warfarin
rapid replacement of coagulation factors eg for dilutional coagulopathy (takes less time than obtaining and thawing FFPs)

Question 22

there a few IgG ABO antibodies that can cross the placenta but not cause HFDN. Why?

Answer 22

foetal red cells have poorly defined ABO antigens which are unable to support binding of ABO antibodies

ABO antigens are found on other cells which “mop up” the IgG antibodies

only occurs when mothers have exceptionally high IgG anti A or Anti B antibodies

IgG antibodies from mother will disappear when baby develops their own IgM ones

Question 23

why are platelets of the same ABO group selected

what is the universal plasma donor

Answer 23

reduce of reaction due to anti A or B antibodies in patient plasma
reduce risk of reaction due to anti A or B antibodies in donor plasma

if no other option platelets of other blood groups can be used as long as it is high titre negative

Group AB

Question 24

which allele for RhD is dominant and recessive

Answer 24

D is dominant and codes for D antigen

d is recessive and codes for no D antigen