Blood Transfusions 2 Flashcards
What are the two categories of adverse reactions to transfusions (2)
Acute < 24 hours
Delayed >24 hours
What are some acute adverse reactions to transfusions (6)
Acute haemolysis (ABO incompatible) Allergic/anaphylaxis Infection (bacterial) Febrile non-haemolytic Respiratory (transfusion associated circulatory overload (TACO), acute lung injury (TRALI)
What are some delayed adverse reactions to transfusions (5)
Delayed haemolytic transfusion reaction (antibodies) Infection (viral, malaria, vCJD) TA-GvHD Post transfusion purpura Iron overload
How are acute transfusion reactions picked up (3)
Many acute reactions start as a rise in temp, or pulse, or fall in BP, even before patient feels symptoms
Symptoms: depends on cause, but can include:
Fever, rigors, flushing, vomiting, dyspnoea, pain at transfusion site, loin pain/ chest pain, urticaria, itching, headache, collapse etc
Monitoring may be the ONLY way to detect reaction if patient unconscious
- Baseline temp, pulse, respiratory rate, BP before transfusion starts
- Repeat after 15 mins (as most, but not all, reactions will start within 15 mins)
- Ideally repeat hourly and at end of transfusion (as occasionally reactions start after transfusion finished)
What are FNHTR
Febrile Non-Haemolytic Transfusion Reaction.
During / soon after transfusion (blood or platelets), rise in temperature of 1C, chills, rigors
Common before blood was leucodepleted, now rarer
How are FNHTR treated (2)
Have to stop or slow transfusion - may need to treat with paracetamol
What is the MOA of FNHTR
White cells can release cytokines during storage
What are allergic transfusion reactions
Common especially with plasma
Mild urticarial or itchy rash sometimes with a wheeze. During or after transfusion.
How are allergic transfusion reactions treated (2)
Have to stop or slow down transfusion
IV antihistamines to treat (and prevent in future, if recurrent)
What causes allergic transfusion reactions (2)
Allergy to a plasma protein in donor so may not recur again, depending on how common the allergen is
Commoner in recipients with other allergies and atopy
What causes acute intravascular haemolyiss
WRONG BLOOD - IgM reaction
What are the symptoms of giving a patient the wrong blood
Restless, chest/ loin pain, fever, vomiting, flushing, collapse, haemoglobinuria (later);
Raised temperature
Raised heart rate
Low BP
What can be some reasons for wrong blood administered for transfusion (3)
Failure of bedside check giving blood
Wrongly labelled blood sample
Lab error
How is wrong blood given at transfusion managed (3)
Take samples for FBC, biochemistry, coagulation, repeat x-match and Direct Antiglobulin Test (DAT).
DISCUSS WITH HAEMATOLOGY ASAP
What are the symptoms of transfusion of bacterial contaminated blood
Restless, fever, vomiting, flushing, collapse
Low BP, high HR, high temp
What causes bacterial contamination of transfused blood (4)
Bacterial growth can cause endotoxin production which causes immediate collapse From the donor (low grade GI, dental, skin infection) Introduced during processing (environmental or skin) Storage temperatures (platelets > red cells > frozen components)
How can we prevent contamination of donor blood (4)
Donor questioning + arm cleaning + diversion of first 20mL into a pouch (used for testing)
Red cells: Store always in controlled fridge 40C; shelf-life 35 days. If out for >½ hour, need to go back in fridge for 6 hours. Complete transfusion of blood within 4.5h of leaving fridge i.e. transfuse over 4hrs max
Platelets: stored at 220C; shelf-life 7 days (as now screened for bacteria before release)
All components: look for abnormalities e.g. clumps of discoloured debris; brown plasma etc
What is post-transfusion anaphylaxis
Immediate reaction
Severe, life threatening reaction soon after start of transfusion
What are the signs of anaphylaxis post transfusion
Low BP and high HR (shock)
Very breathless with wheeze
Often laryngeal and/or facial oedema
What is the mechanism of anaphylaxis following blood transfusion
IgE antibodies in patient cause mast cell release of granules & vasoactive substances. Most allergic reactions are not severe, but some can be e.g. in
IgA deficiency:
What is TACO
Transfusion associated circulatory overload
What occurs in TACO
Pulmonary oedema/fluid overload
When does TACO occur
Often lack of attention to fluid balance, especially in cardiac failure, renal impairment, hypoalbuminaemia, very young and very old
What are the clinical features of TACO
SOB
Low O2 sats
high HR
High BP
What is seen on CXR in TACO (2)
Fluid overload
Cardiac failure
What is TRALI
Transfusion related acute lung injury
What are the clinical features of TRALI
SOB
Low O2 sats
high HR
High BP
What is seen on CXR in TRALI
Bilateral pulmonary infiltrates during/within 6 hours of transfusion due to circulatory overload or other likely causes
What is the MOA of TRALI
Anti-wbc antibodies (HLA or neutrophil Abs) in donor
Interact with corresponding ag on patient’s wbc’s
Aggregates of wbc’s get stuck in pulmonary capillaries → release neutrophil proteolytic enzymes & toxic O2 metabolites → lung damage
How can TRALI be prevented
Male donors for plasma and platelets (no pregnancy or transfusion, so no HLA/HNA antibodies)
What are the two steps involved in delayed haemolytic transfusion reactions
Allommunisation Extravascular haemolysis (as IgG) so takes 5-10 days
What is allommunisation
1-3% of all patients transfused develop an immune antibody to a RBC antigen they lack
What is extravascular haemolysis
If the patient has another transfusion with RBCs expressing the same antigen (that they just became allomminised against), antibodies cause RBC destruction
What is seen in biochemistry tests in delayed haemolytic transfusion reaction
Raised Bilirubin Low Hb High retics Haemoglobinuria over a few days U&Es have to be tested - as can cause renal failure
What infections can be transferred via blood transfusion (3)
Malaria
Viral infection
Variant CJD
What are the features of infections from blood transfusions
Symptoms months or years after
Rely on questioning donors about wellbeing
Never zero risk – so don’t transfuse unnecessarily!
Current estimates of getting viral infection from a donation: hepatitis B – 1 in 1.3 million, HIV – 1 in 6.5 million, hepatitis C – 1: 28 million
What is the risk of CMV from blood transfusion
Very immunosuppressed (stem cell transplant) patients can get fatal CMV disease, but leucodepletion removes CMV (in wbc’s). Only give CMV- now for pregnant women (fetus) & neonates.
What is the risk of parvovirus from blood transfusion
causes temporary red cell aplasia - affects fetuses and patients with haemolytic anaemias eg: sickle cell; hereditary spherocytosis
What is the risk of vCJD from blood transfusion.
no test. Only 4 cases. but blood services exclude transfused patients as donors, as precaution. Also obtain plasma for those born after 01.01.1996, from outside the UK
What are the features of transfusion associated graft-versus-host disease
Rare, but always fatal
Donor’s blood contains some lymphocytes (able to divide)
Normally, patient’s immune system recognises donor’s lymphocytes as ‘foreign’ and destroys them
In ‘susceptible’ patients (eg.. very IS) - lymphocytes not destroyed
Lymphocytes recognise patient’s tissue HLA antigens as ‘foreign’ – so attack patient’s gut, liver, skin and bone marrow -
Causes severe diarrhoea, liver failure, skin desquamation, bone marrow failure death weeks to months post transfusion
How can transfusion associated graft versus host disease be prevented (2)
Irradiate blood components for very immunocompromised or patients having HLA matched components
What is post transfusion purpura
Purpura appears 7-10 days after transfusion of blood or platelets and usually resolves in 1 to 4 weeks but can cause life threatening bleeding
Affects HPA -1a negative patients - previously immunised by pregnancy or transfusion (anti-HPA-1a antibody)
How is post transfusion purpura treated
IVIG
What causes the purpura in post-transfusion purpura
Very low platelets of <20
What is a risk in immune modulation post blood transfusion
Can increase risk of infections post-op and increased recurrence of cancers
What are the features of iron overload following transfusion
If lots of transfusion (eg:>50) over time accumulate iron (not excreted); 200-250mg of iron per unit of blood
Can cause organ damage - liver, heart, endocrine etc
Prevent by iron chelation (exjade) with transfusions once ferritin >1000 eg: used in Thalassaemics - monthly transfusions
How can anti-D be formed (2)
By receiving blood transfusion
In pregnancy - by foetal red cells entering mother’s circulation at delivery or during pregnancy
MOA of RhD sensitisation during the first pregnancy and foetal red cell destruction during the second pregnancy with a RhD positive foetus
1st pregnancy: Foetal RhD positive red cells cross the placenta mainly during delivery. AntiD forms in the mother approximately 6 months later.
2nd pregnancy: RhD positive foetus. Maternal antiD crosses the placenta and coats the foetal RhD positive red cells and destroys them in the foetal spleen and liver.
What are the clinical features of haemolytic disease of the newborn
Only IgG antibodies can cross the placenta.
If mother has high levels of IgG antibody - it can destroy fetal red cells, if they are positive for the corresponding antigen: Fetal anaemia (haemolytic), Haemolytic disease of newborn (anaemia plus high bilirubin - which builds up after birth as no longer removed by placenta)
Sequelae include hydrops fetalis, kernicterus.
How is a pregnancy managed when the mother already has red cell antibody.
All pregnant women have G&S at around 12 weeks (booking) and again at 28 weeks to check for RBC antibodies.
If antibody present:
Check if father has the antigen (so baby could inherit it)
Monitor level of antibody (high or rising - more likely to affect fetus)
Check ffDNA sample
Monitor fetus for anaemia – MCA Doppler ultrasound
Deliver baby early, as HDN gets a lot worse in last few weeks of pregnancy
If necessary, intra-uterine transfusion can be given to the foetus
What are the points where intra uterine transfusion can be given to the foetus (3)
Specialised centres, highly skilled - needle in umbilical vein
At delivery - monitor baby’s Hb and bilirubin for several days as HDN can get worse for few days
Can give exchange transfusion to baby if needed to lower bilirubin and raise Hb; plus phototherapy to lower bilirubin
What is the most important antibody is HDFN
Anti-D
How can sensitisation to anti-D be prevented
Always transfuse RhD negative females of child bearing
potential with RhD negative blood. Can give intra-muscular
injection of anti-D immunoglobulin, at times when mother
is at risk of a fetomaternal bleed e.g. at delivery
How does prophylactic anti-D immunoglobulin work
RhD positive (fetal) red cells get coated with anti-D Ig and then they get removed by the mother’s reticuloendothelial system (spleen) before they can sensitise the mother to produce anti-D antibodies
When is anti-D immunoglobulin effective
Must give anti-D injection within 72 hours of the sensitising event
When is anti-D immunoglobulin not effective
If the mother has already been sensitised in the past
Management: Delivery of RhD positive baby
Give anti-D to mother at delivery
When should you give anti-D to the mother (2)
At delivery if baby is RhD positive
For sensitising events during pregnancy (where HDFN if most likely to occur)
What are some sensitising events for anti-D during pregnancy (5)
Spontaneous miscarriages if surgical evacuation needed and therapeutic terminations
Amniocentesis and chorionic villous sampling
Abdominal trauma (falls and car accidents)
External cephalic version (turning the fetus)
Stillbirth or intrauterine death
What is the dose of anti-D given (3)
At least 250 iu - for events before 20 weeks of pregnancy
At least 500 iu - for events any time after 20 weeks of pregnancy (including delivery)
Sometimes a larger dose is needed for larger bleeds, so an FMH test (Kleihauer test) is always done if > 20 weeks pregnant and at delivery, to determine if more anti-D is needed than the standard dose, if the fetal bleed is large
What dose of anti-D can prevent sensitisation from a 1mL FMH
125iu
What is RAADP
Routine antenatal anti-D prophylxis
Whe is anti-D routinely given
3rd trimester
Usually, dose of 1500iu anti-D Ig at 28-30 weeks.
Can prevent MOST RhD negative women from becoming sensitised
What are the antibodies that can affect the baby during pregnancy (5)
Anti-D, Anti-C, anti-Kell cause severe HDN (anti-D is the worst, Kell causes reticulocytopenia in the foetus as well as haemolysis)
IgG anti-A and anti-B antibodies from Group O mothers can cause mild HDN (usually not severe - phototherapy)
