Indications and contraindications for transfusion in inherited red cell disorders

Question 1

When is a sickle cell patient transfused?

Answer 1

Episodic: Crisis management if Hb is falling
Chronic: Stroke prevention

Question 2

What are the types of transfusion for the sickle cell patient?

Answer 2

Simple: to relieve anaemia/complications, they’re used in crisis only when the Hb rapidly falls by 30g/L e.g. splenic sequestration
Exchange - isovolumetric exchange to remove sicklecells
reduce iron overload and prevent overtransfusion

Question 3

What are the problems with exchange transfusion?

Answer 3

Expensive and needs specialised equipment

Question 4

What can happen to spleen sequestration during trasnfusion? What must be done to facilitate this?

Answer 4

The spleen can release the Hb into the blood

Transfusion should be halted at 50% to check the Hb as over transfusion can lead to sharp increase in viscosity

Question 5

When else do you transfuse in sickle cell?

Answer 5

Acute Chest Crisis
Stroke prevention
Perioperative
Pregnancy

Question 6

How is an acute chest managed?

Answer 6

Transfusion within 48 hours increases the prognosis
Mild/moderate - simple top up
Severe - O2 sats <90% - exchange transfusion

Question 7

How does transfusion improve stroke outcome?

Answer 7

STOP I (1995-97) Regular transfusions reduce stroke risk by 90% in children with abnormal transcranial dopplers
STOP II (2000) Evidence also showed that stopping transfusions once TCD normalises may lead to a reversion to previous risk

Question 8

How does transfusion affect perioperative management?

Answer 8

Transfusion alternatives perioperatively(TAPS trial) in SCD

Transfusing to 100g/L reduces surgical complications when general anaesthesia is used

Question 9

What are the benefits of exchange transfusion?

Answer 9

1. Increase the normal Hb
2. Permitting transfusion of increased volumes of donor RBCs without increasing haematocrit
3. Reduces the net transfused volume -> reduced iron overloading

Question 10

What are the risks of exchange transfusion?

Answer 10

1. Increased donor unit exposure and increase risk of alloimmunisation
2. Higher costs
3. Need specialised equipment
4. Frequent need for permanent venous access

Question 11

What happens with transfusion in beta thal?

Answer 11

Trait - mild anaemia only no need to transfuse
B+intermedia - may need episode transfusion when pt undergoes stress
B0major - lifelong transfusion needed 1/month for survival

Question 12

What happens with transfusion and alpha thal?

Answer 12

HbH - episodic transfusion, often never need

Alpha trait - microcytic but not anaemia don’t need to transfuse

Question 13

What are the common inherited haemolytic anaemias?

Answer 13

G6pd deficiency, PKD, HS, HE

Question 14

Do inherited haemolytic anaemias required transfusion?

Answer 14

Episodic only when there is a severe haemolytic crisis

transfuse only if the anaemia is clinically significant

Question 15

Which bone marrow failure syndrome requires transfusion?

Answer 15

Diamond-Blackfan

Question 16

Describe the acute adverse reactions that occur with transfusions

Answer 16

Severe:
ABO mismatch - severe haemolysis
Anaphylaxis
Bacterial contamination

Moderate/Mild
TACO - transfusion associated circulatory overload
Fever
Allergic reactions

Question 17

Describe the delayed adverse reactions

Answer 17

Delayed haemolytic transfusion reaction
Alloimmunisation
GVHD - 95% fatal 
Infection
Iron Overload

Question 18

Why are transfusions needed?

Answer 18

1. increase Hb to relieve sever anaemia
2. Replace poor quality RBCs with non sickle RBCs
3. Suppress extramedullary haemopoiesis e.g. betal thal major

Question 19

What types of matching is there for blood groups?

Answer 19

Standard - ABO and Rh
Phenotype - Above and absence of alloantibodies
Extended - Match for ABO, Rh, Kell. This is with the aim to prevent alloantibody generation

Question 20

What is the process for production of alloantibodies?

Answer 20

Initial exposure - slow response

Subsequent - Rapid antibody production and haemolysis

Question 21

Why is alloantibody production higher in SCD patients?

Answer 21

Because the donor pools are unlikely to share the same ethnic origin so less matching

Question 22

Explain the clinicopathological features of immediate transfusion reactions. Give an example antibody and its effect (4 marks?)

Answer 22

-Intravascular haemolysis
-Most often caused by ABO incompatability
-features include: abrupt onset of fever, chills, back pain, pain at infusion site, hypotension, DIC
//-Anaphylaxis is another kind of reaction

Question 23

Explain the DAT (Direct antiglobulin test/ Coomb’s test)

Answer 23

• Antigen and antibody reaction test to detect the presence of anti RBC antibodies, using coomb’s reagent
• Is used to test for a possible acute or delayed heamolytic transfusion reaction
• ie is used clinically when immune-mediated heamolytic anemia (antibody-mediated destruction of RBCs) is suspected

Question 24

Explain the delayed haemolytic transfusion reaction. Will DAT be positive? (Coombs)

Answer 24

These reactions occur in patients who have been alloimmunized to minor RBC antigens during previous transfusions and/or pregnancies; pretransfusion testing fails to detect these alloantibodies due to their low titer. -Following re-exposure to antigen positive RBCs, a response occurs, with a rapid rise in antibodies.
-This leads to extravascular haemolysis (Taken up by spleen), a fever and a falling haematocrit
DAT is positive due to the presence of antobodies