Indications and contraindications for transfusion in inherited red cell disorders Flashcards
When is a sickle cell patient transfused?
Episodic: Crisis management if Hb is falling
Chronic: Stroke prevention
What are the types of transfusion for the sickle cell patient?
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
What are the problems with exchange transfusion?
Expensive and needs specialised equipment
What can happen to spleen sequestration during trasnfusion? What must be done to facilitate this?
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
When else do you transfuse in sickle cell?
Acute Chest Crisis
Stroke prevention
Perioperative
Pregnancy
How is an acute chest managed?
Transfusion within 48 hours increases the prognosis
Mild/moderate - simple top up
Severe - O2 sats <90% - exchange transfusion
How does transfusion improve stroke outcome?
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
How does transfusion affect perioperative management?
Transfusion alternatives perioperatively(TAPS trial) in SCD
Transfusing to 100g/L reduces surgical complications when general anaesthesia is used
What are the benefits of exchange transfusion?
- Increase the normal Hb
- Permitting transfusion of increased volumes of donor RBCs without increasing haematocrit
- Reduces the net transfused volume -> reduced iron overloading
What are the risks of exchange transfusion?
- Increased donor unit exposure and increase risk of alloimmunisation
- Higher costs
- Need specialised equipment
- Frequent need for permanent venous access
What happens with transfusion in beta thal?
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
What happens with transfusion and alpha thal?
HbH - episodic transfusion, often never need
Alpha trait - microcytic but not anaemia don’t need to transfuse
What are the common inherited haemolytic anaemias?
G6pd deficiency, PKD, HS, HE
Do inherited haemolytic anaemias required transfusion?
Episodic only when there is a severe haemolytic crisis
transfuse only if the anaemia is clinically significant
Which bone marrow failure syndrome requires transfusion?
Diamond-Blackfan
Describe the acute adverse reactions that occur with transfusions
Severe:
ABO mismatch - severe haemolysis
Anaphylaxis
Bacterial contamination
Moderate/Mild
TACO - transfusion associated circulatory overload
Fever
Allergic reactions
Describe the delayed adverse reactions
Delayed haemolytic transfusion reaction Alloimmunisation GVHD - 95% fatal Infection Iron Overload
Why are transfusions needed?
- increase Hb to relieve sever anaemia
- Replace poor quality RBCs with non sickle RBCs
- Suppress extramedullary haemopoiesis e.g. betal thal major
What types of matching is there for blood groups?
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
What is the process for production of alloantibodies?
Initial exposure - slow response
Subsequent - Rapid antibody production and haemolysis
Why is alloantibody production higher in SCD patients?
Because the donor pools are unlikely to share the same ethnic origin so less matching
Explain the clinicopathological features of immediate transfusion reactions. Give an example antibody and its effect (4 marks?)
-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
Explain the DAT (Direct antiglobulin test/ Coomb’s test)
- 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
Explain the delayed haemolytic transfusion reaction. Will DAT be positive? (Coombs)
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
