Blood Products

Question 1

What is a blood product?

Answer 1

A blood product is any part of the blood that is collected from a donor for use in a blood transfusion.

Question 2

Briefly describe the NICE current guidelines on blood cell transfusions

Answer 2

Current NICE guidelines recommend a restrictive haemoglobin concentration threshold of 70 g/L for those who need red blood cell transfusions (without any major haemorrhage or acute coronary syndrome) and a haemoglobin concentration target of 70-90 g/L after transfusion.

Question 3

What are the 2 important blood groups for blood transfusions?

Answer 3

In blood transfusions, there are two important blood groups, the ABO blood system and the group D of the rhesus system.

Question 4

Briefly describe ‘Rhesus D (RhD) Group’

Answer 4

A patient’s blood group can initially be classified as ‘RhD+’ or ‘RhD-‘: this refers the presence or absence of Rhesus D surface antigens on the red blood cells (RBC). Approximately 85% of the population is RhD+ (they have RhD antigens present) and 15% are RhD– (RhD antigens are absent).

A RhD- patient will make RhD antibody if they are given RhD+ blood. Clearly, this will not matter for the patient; a RhD- patient, who is given RhD+ blood, and therefore makes anti-D, cannot then go on to attack their own red blood cells as they do not have RhD present on their RBC membrane.

Question 5

Briefly describe haemolytic disease of the newborn (HTN)

Answer 5

RHD grouping can cause potential problems during pregnancy as anti-D antibodies can cross the placenta, such as may occur in the following example:

• A woman is born with RhD- blood. Her partner is RhD+ and she becomes pregnant with a fetus that is also RhD+. During childbirth, she comes into contact with the foetal (Rh+ve) blood and develops antibodies to it.
• She later becomes pregnant with a second child that is also Rh +ve.
• The woman’s anti-D antibodies cross the placenta during this pregnancy and enter the foetal circulation, which contains RhD+ blood, and bind to the foetus’ RhD antigens on its RBC surface membranes.
• This causes the foetal immune system to attack and destroy its own RBCs, leading to foetal anaemia. This is termed haemolytic disease of the newborn (HDN).

We therefore give RhD specific blood to women in order to avoid HDN. In men, this is clearly not a concern so, although it is preferable to give correctly cross-matched blood, it is possible to give a RhD- male some RhD+ blood if that is all that is available in an emergency setting.