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Kat's Pathology > Blood Transfusions 2 > Flashcards

Blood Transfusions 2 Flashcards

1
Q

What are the two categories of adverse reactions to transfusions (2)

A

Acute < 24 hours

Delayed >24 hours

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2
Q

What are some acute adverse reactions to transfusions (6)

A 
Acute haemolysis (ABO incompatible) 
Allergic/anaphylaxis
Infection (bacterial)
Febrile non-haemolytic
Respiratory (transfusion associated circulatory overload (TACO), acute lung injury (TRALI)
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3
Q

What are some delayed adverse reactions to transfusions (5)

A 
Delayed haemolytic transfusion reaction (antibodies) 
Infection (viral, malaria, vCJD)
TA-GvHD
Post transfusion purpura 
Iron overload
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4
Q

How are acute transfusion reactions picked up (3)

A

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)
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5
Q

What are FNHTR

A

Febrile Non-Haemolytic Transfusion Reaction.

During / soon after transfusion (blood or platelets), rise in temperature of 1C, chills, rigors
Common before blood was leucodepleted, now rarer

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6
Q

How are FNHTR treated (2)

A

Have to stop or slow transfusion - may need to treat with paracetamol

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7
Q

What is the MOA of FNHTR

A

White cells can release cytokines during storage

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8
Q

What are allergic transfusion reactions

A

Common especially with plasma

Mild urticarial or itchy rash sometimes with a wheeze. During or after transfusion.

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9
Q

How are allergic transfusion reactions treated (2)

A

Have to stop or slow down transfusion

IV antihistamines to treat (and prevent in future, if recurrent)

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10
Q

What causes allergic transfusion reactions (2)

A

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

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11
Q

What causes acute intravascular haemolyiss

A

WRONG BLOOD - IgM reaction

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12
Q

What are the symptoms of giving a patient the wrong blood

A

Restless, chest/ loin pain, fever, vomiting, flushing, collapse, haemoglobinuria (later);
Raised temperature
Raised heart rate
Low BP

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13
Q

What can be some reasons for wrong blood administered for transfusion (3)

A

Failure of bedside check giving blood
Wrongly labelled blood sample
Lab error

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14
Q

How is wrong blood given at transfusion managed (3)

A

Take samples for FBC, biochemistry, coagulation, repeat x-match and Direct Antiglobulin Test (DAT).

DISCUSS WITH HAEMATOLOGY ASAP

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15
Q

What are the symptoms of transfusion of bacterial contaminated blood

A

Restless, fever, vomiting, flushing, collapse

Low BP, high HR, high temp

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16
Q

What causes bacterial contamination of transfused blood (4)

A 
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)
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17
Q

How can we prevent contamination of donor blood (4)

A

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

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18
Q

What is post-transfusion anaphylaxis

A

Immediate reaction

Severe, life threatening reaction soon after start of transfusion

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19
Q

What are the signs of anaphylaxis post transfusion

A

Low BP and high HR (shock)
Very breathless with wheeze
Often laryngeal and/or facial oedema

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20
Q

What is the mechanism of anaphylaxis following blood transfusion

A

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:

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21
Q

What is TACO

A

Transfusion associated circulatory overload

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22
Q

What occurs in TACO

A

Pulmonary oedema/fluid overload

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23
Q

When does TACO occur

A

Often lack of attention to fluid balance, especially in cardiac failure, renal impairment, hypoalbuminaemia, very young and very old

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24
Q

What are the clinical features of TACO

A

SOB
Low O2 sats
high HR
High BP

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25
Q

What is seen on CXR in TACO (2)

A

Fluid overload

Cardiac failure

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26
Q

What is TRALI

A

Transfusion related acute lung injury

27
Q

What are the clinical features of TRALI

A

SOB
Low O2 sats
high HR
High BP

28
Q

What is seen on CXR in TRALI

A

Bilateral pulmonary infiltrates during/within 6 hours of transfusion due to circulatory overload or other likely causes

29
Q

What is the MOA of TRALI

A

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

30
Q

How can TRALI be prevented

A

Male donors for plasma and platelets (no pregnancy or transfusion, so no HLA/HNA antibodies)

31
Q

What are the two steps involved in delayed haemolytic transfusion reactions

A 
Allommunisation 
Extravascular haemolysis (as IgG) so takes 5-10 days
32
Q

What is allommunisation

A

1-3% of all patients transfused develop an immune antibody to a RBC antigen they lack

33
Q

What is extravascular haemolysis

A

If the patient has another transfusion with RBCs expressing the same antigen (that they just became allomminised against), antibodies cause RBC destruction

34
Q

What is seen in biochemistry tests in delayed haemolytic transfusion reaction

A 
Raised Bilirubin 
Low Hb
High retics 
Haemoglobinuria over a few days 
U&amp;Es have to be tested - as can cause renal failure
35
Q

What infections can be transferred via blood transfusion (3)

A

Malaria
Viral infection
Variant CJD

36
Q

What are the features of infections from blood transfusions

A

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

37
Q

What is the risk of CMV from blood transfusion

A

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.

38
Q

What is the risk of parvovirus from blood transfusion

A

causes temporary red cell aplasia - affects fetuses and patients with haemolytic anaemias eg: sickle cell; hereditary spherocytosis

39
Q

What is the risk of vCJD from blood transfusion.

A

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

40
Q

What are the features of transfusion associated graft-versus-host disease

A

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

41
Q

How can transfusion associated graft versus host disease be prevented (2)

A

Irradiate blood components for very immunocompromised or patients having HLA matched components

42
Q

What is post transfusion purpura

A

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)

43
Q

How is post transfusion purpura treated

A

IVIG

44
Q

What causes the purpura in post-transfusion purpura

A

Very low platelets of <20

45
Q

What is a risk in immune modulation post blood transfusion

A

Can increase risk of infections post-op and increased recurrence of cancers

46
Q

What are the features of iron overload following transfusion

A

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

47
Q

How can anti-D be formed (2)

A

By receiving blood transfusion

In pregnancy - by foetal red cells entering mother’s circulation at delivery or during pregnancy

48
Q

MOA of RhD sensitisation during the first pregnancy and foetal red cell destruction during the second pregnancy with a RhD positive foetus

A

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.

49
Q

What are the clinical features of haemolytic disease of the newborn

A

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.

50
Q

How is a pregnancy managed when the mother already has red cell antibody.

A

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

51
Q

What are the points where intra uterine transfusion can be given to the foetus (3)

A

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

52
Q

What is the most important antibody is HDFN

A

Anti-D

53
Q

How can sensitisation to anti-D be prevented

A

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

54
Q

How does prophylactic anti-D immunoglobulin work

A

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

55
Q

When is anti-D immunoglobulin effective

A

Must give anti-D injection within 72 hours of the sensitising event

56
Q

When is anti-D immunoglobulin not effective

A

If the mother has already been sensitised in the past

57
Q

Management: Delivery of RhD positive baby

A

Give anti-D to mother at delivery

58
Q

When should you give anti-D to the mother (2)

A

At delivery if baby is RhD positive

For sensitising events during pregnancy (where HDFN if most likely to occur)

59
Q

What are some sensitising events for anti-D during pregnancy (5)

A

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

60
Q

What is the dose of anti-D given (3)

A

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

61
Q

What dose of anti-D can prevent sensitisation from a 1mL FMH

A

125iu

62
Q

What is RAADP

A

Routine antenatal anti-D prophylxis

63
Q

Whe is anti-D routinely given

A

3rd trimester
Usually, dose of 1500iu anti-D Ig at 28-30 weeks.

Can prevent MOST RhD negative women from becoming sensitised

64
Q

What are the antibodies that can affect the baby during pregnancy (5)

A

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)

Kat's Pathology (105 decks)

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