Haem: Blood Tranfusions 2 Flashcards
How are acute and delayed transfusion reactions defined?
Acute < 24 hours
Delayed > 24 hours
List some causes of acute transfusion reactions.
- Acute haemolytic (ABO incompatibility)
- Allergic/anaphylaxis
- Infection (bacterial)
- Febrile non-haemolytic
- Respiratory (TACO, TRALI)
TACO - Transfusion associated cardiovascular overload
TRALI - Transfusion related acute lung injury
List some causes of delayed transfusion reactions.
- Delayed haemolytic transfusion reaction
- Infection (viral, malaria, vCJD)
- TA-GvHD
- Post-transfusion purpura
- Iron overload
What are some early clinical signs that might be suggestive of acute transfusion reaction?
- Rise in temperature
- Tachycardia
- Fall in BP
NOTE: these can occur before the patient experiences any symptoms
List some symptoms of an acute transfusion reaction.
- Fever
- Rigors
- Flushing
- Vomiting
- Dyspnoea
- Pain at transfusion site
- Chest pain
- Urticaria and itching
- Collapse
If the patient is unconscious, how might you detect an early transfusion reaction?
- Baseline temperature, pulse, RR and BP before transfusion
- Repeat every 15 mins (most reactions start within 15 mins)
- Repeat hourly and at the end of the transfusion
What are the clinical features of a febrile non-haemolytic transfusion reaction?
- Occurs during/soon after transfusion (of blood or platelets)
- Rise in temperature, chills and rigors
Unpleasant, but not life-threatening
What causes febrile non-haemolytic transfusion reactions?
Release of cytokines from white cell during storage
NOTE: this used to be common before blood was leucodepleted
How is febrile non-haemolytic transfusion reaction treated?
Slow/stop the transfusion and treated with paracetamol
Describe the clinical features of an allergic transfusion reaction.
- Mild urticarial or itchy rash
- Sometimes causes a wheeze
Common especially with plasma transfusions
How is an allergic transfusion reaction managed?
- Stop or slow the transfusion
- IV antihistamines
What usually causes allergic transfusion reactions?
Allergy to donor plasma proteins
NOTE: it is more common in patients with a history of atopic disease and it may not recur
List some symptoms of an acute haemolytic transfusion reaction.
Symptoms
- Chest/loin pain
- Fever
- Vomiting
- Flushing
- Collapse
- Haemoglobinuria (later)
Obs
- Low BP
- High HR
- High Temp
In an acute haemolytic transfusion reaction, why is it important to take a blood sample?
Send for FBC, biochemistry, coagulation, repeat X-match and DAT
What is the cause of acute haemolytic transfusion reaction?
Tranfusion of wrong ABO blood group leading to IgM-mediated intravascular haemolysis
How does bacterial contamination from donated blood products present?
Similarly to sepsis/ABO mismatch
- Fever
- Vomiting
- Flushing
- Collapse
Obs (shock)
- Low BP
- Increased HR
- Increased temperature
What happens when bacteria infect donated blood products?
- Bacteria can produce an endotoxin that causes immediate collapse
- The bacteria could have come from the donor or from the processing of blood products
List blood products in order of likelihood of getting contaminated?
- Platelets (most likely)
- RBCs
- Plasma (least likely)
What measures can be taken to reduce the likelihood of bacterial contamination?
- Donor questioning
- Arm cleaning
- Diversion of first 20 mL into a pouch
Describe the storage and shelf-life of RBCs.
- Stored in 4 degree fridge for 35 days
- If kept out for >30 mins -> cannot be re-stored
- Complete transfusion must take place within 4.5 hours of leaving the fridge
Describe the storage and shelf-life of platelets.
Stored at 22 degrees for 7 days
NOTE: they are screened for bacteria before release
What are clincial features of anaphylactic reaction to blood products.
Severe and life-threatening reaction that starts soon after start of transfusion
- Occurs within seconds/minutes
- Drop in BP
- Rise in HR
- Very breathless with a wheeze
- Laryngeal or facial oedema
NOTE: most allergic reactions to blood products are not this severe
What is the mechanism of anaphylactic reaction to blood products?
Caused by IgE-mediated mast cell degranulation
Which patient group is more likely to have severe allergic reactions to blood products?
IgA deficient patients - anti-IgA antibodies may develop in response to exposure to IgA in donor’s blood
Most likely to occur with plasma transfusion
What are the signs of transfusion associated circulatory overload (TACO)? When does it present?
Signs are due to pulmonary oedema/fluid overload
- SoB
- Low oxygen saturations
- High HR
- High BP
- Raised JVP
Usually caused by a lack of attention to fluid balance (especially in cardiac failure, hypoalbuminaemia, extremes of age)
Presents within 6 hours of transfusion
NOTE: this is the most common pulmonary complication to transfuson
What are the CXR features of TACO?
Fluid overload
Cardiac failure
What are the main clinical features of TRALI?
Looks like ARDS
- SoB
- Drop in oxygen saturation
- Rise in HR
- Rise in BP
What CXR features would you expect to see in TRALI?
Bilateral pulmonary infiltrates within 6 hours of transfusion, NOT due to circulatory overload and other causes.
Outline the mechanism of TRALI.
- Anti-WBC antibodies (HLA or neutrophil) in donor blood interact with WBC in the patient
- Results in release of neutrophil proteolytic enzymes and toxic oxygen metabolites in the pulmonary vasculature
- This leads to lung damage
Mechanism actually not fully understood
What are the main differences between TACO and TRALI?
JVP - raised in TACO, not in TRALI
Furosemide - response in TACO, not in TRALI
How can TRALI be avoided?
Using male donors (haven’t been pregnant) who haven’t had a transplant or transfusion so they will not have produced antibodies against HLA
What is alloimmunisation?
- The process of developing antibodies against an antigen
- 1-3% of people receiving transfusions will develop antibodies against an RBC antigen that they lack
What are the consequences of alloimmunisation with regards to blood transfusions?
Delayed haemolytic transfusion reaction
- Repeat transfusion with blood containing the antigen will lead to extravascular haemolysis
- This is IgG mediated so will take 5-10 days
What are the typical blood test results you expect to see during a haemolytic episode?
- High bilirubin
- Low haemoglobin
- High reticulocytes
- High LDH
- Positive DAT
- Haemoglobinuria (for a few days until haemolysis stops)
NOTE: U&E should be tested to check for renal failure. Also group and screen should be repeated to check for the development of new antibodies
In which patient groups is CMV dangerous?
- Very immunosuppressed (e.g. SCT)
- Pregnant women
- Neonates
Usually removed by routine leukodepletion
What is the dangerous effect of parvovirus infection?
Causes temporary red cell aplasia
Which patients are most affected by parvovirus infection?
- Foetuses
- Patients with haemolytic anaemia (e.g. sickle cell disease)
What precaution can be made by blood donation services to prevent transmission of vCJD?
Blood services exclude people who have had transfusions in the past as donors.
Describe the mechanism of transfusion-associated GvHD
- Donor blood will contain some lymphocytes that are capable of dividing
- Normally, the patient’s immune system will recognise and destroy these foreign lymphocytes
- In the very immunosuppressed patients, the donor lymphocytes are not destroyed
- They begin to recognise patient HLA as foreign and begins attacking it
- This damages the gut, liver, skin and bone marrow
NOTE: this is always fatal
What are the clinical manifestations of transfusion-associated Graft-versus-Host disease?
- Severe diarrhoea
- Liver failure
- Skin desquamation
- Bone marrow failure
Death then occurs within weeks to months
How can transfusion-associated graft-versus-host disease be prevented?
Irradiate blood components for very immunocompromised patients
(or HLA matched blood components)
At what point after transfusion does post-transfusion purpura happen?
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
Which patient group tends to be affected by post-transfusion purpura (PTP)?
- 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
How is post-transfusion purpura treated?
IVIG
How much iron is there in a unit of blood?
200-250 mg
How can iron overload be prevented?
Iron chelators (e.g. desferrioxamine)
Used when once ferritin >1000
What are the consequences of iron overload?
End organ damage affectin heart, liver, endocrine organs
What is haemolytic disease of the foetus and newborn?
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
What are some complication haemolytic diease of foetus and newborn?
- Severe foetal anaemia
- Hydrops fetalis
- Kernicterus
When should all women have a group and screen during pregnancy?
- 12 weeks (booking)
- 28 weeks
If anti-D antibodies are detected in a pregnant women, what further steps should be taken?
- 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
What intervention may be performed if the foetus is found to be very anaemic?
Intrauterine transfusion into the umbilical vein
How can haemolytic disease of the newborn be prevented?
- 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
Outline the mechanism of action of anti-D immunoglobulin.
- 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
List some occasions in which anti-D immunoglobulin should be given.
- 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
What doses of anti-D tend to be given?
Less than 20 weeks = 250 iU
More than 20 weeks = 500 iU
Which test is done if a sensitising event occurs >20 weeks to determine if more anti-D is needed?
Kleihauer test
When should anti-D be routinely given to RhD-negative women?
500 iU at 28 weeks and 34 weeks
OR
1500 iU at 28-30 weeks
List some other antibodies (aside from RhD) that can cause haemolytic disease of the newborn.
- 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)
