Blood Transfusion

Question 1

Why is the ABO system so important?

Answer 1

We have naturally occurring antibodies against any antigen NOT present on our own cells
The antibodies are reactive at 37degrees and can cause potentially fatal haemolysis

Question 2

How are A and B antigens formed?

Answer 2

Adding a sugar residue onto a common glycoprotein and fucose stem (H antigen) on the red cell membrane

Question 3

What does groups O consist of?

Answer 3

H stem only

Neither A or B sugars

Question 4

How are antigens determined?

Answer 4

Corresponding genes

Question 5

What does the A gene code for?

Answer 5

An enzyme the adds N-acetyl galactosamine to the common H antigen
Co-dominant

Question 6

What does the B gene code for?

Answer 6

An enzyme that adds galactose

Co-dominant

Question 7

Why is group O safe to give in an emergency?

Answer 7

No ABO antigens

Question 8

What are the features of the Rh system?

Answer 8

Most important antigen is D

Blood groups: RhD positive (have the D antigen) or RhD negative

Question 9

What are the genes for the RhD group?

Answer 9

D gene oceans for D antigen on red cell membrane

d gene codes for no antigen and is recessive (no actual antigen)

Question 10

What are the possible genotypes for RhD?

Answer 10

Positive- DD or Dd

Negative- dd

Question 11

When is it possible for RhD negative people to make anti-D antibodies?

Answer 11

After exposure to the RhD antigen
Either by transfusion of RhD positive blood
Or if a woman is pregnant with a RhD positive foetus

Question 12

What are the implication of anti-D antibodies?

Answer 12

Future transfusion must have RhD negative blood

Can cause HDN (haemolytic disease of the newborn)

Question 13

How is HDN caused?

Answer 13

If a RhD negative mother has anti-D from first pregnancy
In next pregnancy, if the foetus is RhD positive, the mothers anti-D antibodies can cross the placenta
Attach to the RhD positive red cells and cause haemolysis of foetal red cells

Question 14

What can severe HDN cause?

Answer 14

Hydrops fetalis and death

Question 15

What can less-severe HDN cause?

Answer 15

The baby survives but after both the high bilirubin levels can cause brain damage or death

Question 16

How can sensitisation of RhD negative patients be avoided?

Answer 16

Transfuse blood of same RhD group

Group o-neg (RhD negative) used as emergency blood when a patients blood group not known

Question 17

What percentage of donors are O-neg?

Answer 17

6-7%

Question 18

Are there other red cell antigens present?

Answer 18

There are dozens e.g. Rh group-C,c,E,e; Kell, Duffy, Kidd etc.
Do not routinely match for all of them
8% patients transfused will form an antibody to one or more antigens
Once antigen is formed corresponding antigen negative blood must be used

Question 19

Who is blood collected from?

Answer 19

Volunteer
Unpaid
17-70 year olds

Question 20

What would exclude someone from donating?

Answer 20

Diseases that would make giving blood hazardous for them e.g. Cardiovascular or Neurological

If blood would be hazardous for recipient e.g. risks of viral, bacterial or parasitic infections.

Question 21

What are the tests undertaken on donating blood?

Answer 21

Group and Screening

Infection test

Question 22

What is the most important step in maintaining a safe blood supply?

Answer 22

Self-exclusion of individuals at high risk of transmitting blood-borne agents.
Since no test can pick up all infections especially early ones

Question 23

What is prion disease?

Answer 23

A disease caused by prion proteins of variant Creutzfeldt-Jacob disease.
4 cases where donors who were entirely well donated bt developed the disease years later.
No test yet

Question 24

How much blood is collected from a donor?

Answer 24

450ml

Question 25

Why is is not effective to use ‘whole blood’?

Answer 25

Most patients need only one of the component of blood

Allows for more efficient use of donations and less waste

Question 26

What is 1 unit?

Answer 26

Whole blood or blood products derived from one single blood donation

Question 27

What are the main features of red cells?

Answer 27

Cells packages in SAGM nutrients, fluid plasma remover
Shelf life 5 week
Stored at 4 degrees
Given through a blood giving set that has a filter to remove clumps/debris
Rarely need frozen cells

Question 28

What are the main features of fresh frozen plasma?

Answer 28

Stored at -30 degrees frozen within 6h of donation
Shelf lefe 3years
Must thaw 20-30 mins before use
Give ASAP within an hour or coagulation factors degenerate
Dose 12-15ml/kg
Need to know blood group

Question 29

What are the main features of cryoprecipitate?

Answer 29

From frozen plasma thawed at 4-8 degrees overnight, residue remains
Contains fibrinogen and factor VIII
Storage and shelf life same as FFP
Standard dose from 10 donors

Question 30

What are the two forms of Platelet concentrates?

Answer 30

Pooled platelets- from 4 donation pooled to constitute a single adult dose
From a single donor on a cell separator machine- equivalent to 4 single donations

Question 31

What are the main features of platelet concentrates?

Answer 31

Stored at 22 degress
Constantly agitated
Shelf life 7 days
Need to know blood group

Question 32

What are the main features of blood products by fractionation of plasma?

Answer 32

Large pool of plasma from 1000s of donors fractionated

Question 33

What can be gained from fractionation of plasma?

Answer 33

Factor VIII and IX
-For haemophilia A and B

Immunoglobulins

• intramuscular, specific, fractionated from plasm from selected donor who have a high titre of specific antibody
• intramuscular, normal, broad mix in population e.g. to protect against hep A
• intravenous, can be used in some autoimmune disorders

Albumin

• 4.5% useful in burns, plasma exchanges
• 20% for certain severe liver and kidney conditions