Haem: Blood Tranfusions Pt.5

Question 1

How can transfusion-associated graft-versus-host disease be prevented?

Answer 1

Irradiate blood components for very immunocompromised patients
(or HLA matched blood components)

Question 2

At what point after transfusion does post-transfusion purpura happen?

Answer 2

7-10 days after transfusion of platelets or red blood cells

NOTE: it usually resolves in 1-4 weeks but can cause life-threatening bleeding

Question 3

Which patient group tends to be affected by post-transfusion purpura (PTP)?

Answer 3

• HPA-1a negative patients who have previously been immunised by pregnancy or transfusion
• These patients produce anti-HPA-1a antibodies
• These then attack donor AND patient platelets

Question 4

How is post-transfusion purpura treated?

Answer 4

IVIG

Question 5

How much iron is there in a unit of blood?

Answer 5

200-250 mg

Question 6

How can iron overload be prevented?

Answer 6

Iron chelators (e.g. desferrioxamine)

Used when once ferritin >1000

Question 7

What are the consequences of iron overload?

Answer 7

End organ damage affectin heart, liver, endocrine organs

Question 8

What is haemolytic disease of the foetus and newborn?

Answer 8

Anaemia and high bilirubin in the newborn caused by delayed haemolytic reaction from maternal antibodies

NOTE: anti-D is the most important antibody for causing haemolytic disease of the newborn

Question 9

What are some complication haemolytic diease of foetus and newborn?

Answer 9

• Severe foetal anaemia
• Hydrops fetalis
• Kernicterus

Question 10

When should all women have a group and screen during pregnancy?

Answer 10

• 12 weeks (booking)
• 28 weeks

Question 11

If anti-D antibodies are detected in a pregnant women, what further steps should be taken?

Answer 11

• Check if the father has the antigen
• Monitor the level of antibody
• Check cffDNA
• Monitor foetus for signs of anaemia (MCA doppler ultrasound)
• Deliver the baby early because it gets a lot worse around term

Question 12

What intervention may be performed if the foetus is found to be very anaemic?

Answer 12

Intrauterine transfusion into the umbilical vein

Question 13

How can haemolytic disease of the newborn be prevented?

Answer 13

• If an RhD-negative woman of childbearing age needs a blood transfusion, always use RhD-negative blood
• Prophylactic anti-D given 28 and 34 weeks gestation
• IM anti-D can be given at times of possible sensitising events

NOTE: for anti-D immunoglobulin to be effective, it needs to be given within 72 hours of a sensitising event and it does not work if the mother has already developing anti-D antibodies

Question 14

Outline the mechanism of action of anti-D immunoglobulin.

Answer 14

• RhD-positive cells of the foetus get coated by exogenous anti-D
• These will then be removed by the mother’s reticuloendothelial system (spleen) before they can sensitise the mother’s immune system

Question 15

List some occasions in which anti-D immunoglobulin should be given.

Answer 15

• At delivery if the baby is found to be RhD-positive
• Spontaneous miscarriages if surgical evacuation was needed
• Surgical termination of pregnancy
• Amniocentesis and chorionic villous sampling
• Abdominal trauma
• External cephalic version
• Stillbirth or intrauterine death

Question 16

What doses of anti-D tend to be given?

Answer 16

Less than 20 weeks = 250 iU

More than 20 weeks = 500 iU

Question 17

Which test is done if a sensitising event occurs >20 weeks to determine if more anti-D is needed?

Answer 17

Kleihauer test

Question 18

When should anti-D be routinely given to RhD-negative women?

Answer 18

500 iU at 28 weeks and 34 weeks
OR
1500 iU at 28-30 weeks

Question 19

List some other antibodies (aside from RhD) that can cause haemolytic disease of the newborn.

Answer 19

• Anti-c and anti-Kell can cause severe HDN (less severe than RhD)
• Anti-Kell causes haemolysis and reticulocytopaenia in the foetus
• IgG anti-A and anti-B can cause mild HDN in group O mothers (usually treated with phototherapy)