Haem: Blood Tranfusions 2 Flashcards
What is the difference between acute and delayed transfusion reactions?
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 and TRALI)
List some causes of delayed transfusion reactions.
- Delayed haemolytic transfusion reaction
- Infection (viral, malaria, vCJD)
- TA-GvHD
- Post-transfusion purura
- Iron overload
What is the most common transfusion reaction?
Transplant-associated circulatory overload (TACO)
What are some early features that might be suggestive of acute transfusion reaction?
- Rise in temperature or pulse
- 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
- 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
NOTE: this used to be common before blood was leucodepleted
What causes febrile non-haemolytic transfusion reactions?
Release of cytokines from white cell during storage
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
How is an allergic transfusion reaction managed?
- Stop or slow the transfusion
- IV antihistamines
What usually causes allergic transfusion reactions?
Allergy to plasma protein in the donor
NOTE: it is more common in patients with a history of atopic disease and it may not recur
Which blood product is most likely to cause an allergic transfusion reaction?
Plasma
List some symptoms of an acute haemolytic transfusion reaction.
- Chest/loin pain
- Fever
- Vomiting
- Flushing
- Collapse
- Haemoglobinuria
- 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
How does bacterial contamination from donated blood products present?
Similarly to ABO mismatch
What causes bacterial infection from 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 a 4 degree fridge for 35 days
- If it is kept out for > 30 mins it cannot go back in the fridge
- 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 relase
Describe the clinical features you would expect to see in an anaphylactic reaction to blood products.
- Occurs soon after starting transfusion
- Drop in BP
- Rise in HR
- Very breathless with a wheeze
- Laryngeal or facial oedema
NOTE: it is caused by IgE-mediated mast cell degranulation
NOTE: most allergic reactions are not this severe
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)
What causes TACO and what are the main clinical features?
- Usually caused by a lack of attention to fluid balance (especially in cardiac failure, hypoalbuminaemia, extremes of age)
- Leads to pulmonary oedema
- SOB
- Low oxygen saturations
- High HR
- High BP
NOTE: this is very common
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 due to circuloatry overload and other causes.
Outline the mechanism of TRALI.
- Anti-WBC antibodies in donor blood interact with WBC in the patient
- Aggregates of WBCs get stuck to pulmonary capillaries resulting in the release of neutrophil proteolytic enzymes and toxic oxygen metabolites
- This leads to lung damage
What are the main differences between TACO and TRALI?
JVP is not raised and the patient will not respond to frusemide in TRALI
How can TRALI be avoided?
Using male donors (haven’t been pregnant) who haven’t had a transplant so they will not have produced antibodies against HLA
What is alloimmunisation?
The process of developing antibodies against an antigen
NOTE: 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?
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
- 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
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 anaeamis (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-assocaited Graft-versus-Host disease.
- 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 susceptible patients (very immunosuppressd), the lymphocytes are not destroyed
- They begin to recognise patient HLA as foreign and begins attacking it (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?
- Diarrhoea
- Liver failure
- Skin desquamation
- Bone marrow failure
- Death (weeks to months)
How can transfusion-associated Graft-versus-Host disease be prevented?
Irradiate blood components for very immunocompromised patients
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?
HPA-1a negative patients who have previously been immunised by pregnancy or transfusion
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. exjade)
What is haemolytic disease of the newborn?
Anaemia and high bilirubin in the newborn
NOTE: the bilirubin builds up in the newborn after birth because they no longer have a placenta to remove it
When should all women have a group and screen during pregnancy?
12 weeks
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
NOTE: anti-D is the most important antibody for causing haemolytic disease of the newborn
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
- IM anti-D immunoglobulin 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 devliery 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?
Usually 500 iU at 28 weeks and 34 weeks
NOTE: can also be 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)
