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Path - Immuno > Blood transfusion > Flashcards

Blood transfusion Flashcards

1
Q

how are ABO groups are determined?

A
  1. by the antigens (sugars) on the red cell membrane.

2. the naturally-occurring antibodies (IgM) in the plasma.

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2
Q

If you give an ABO incompatible blood transfusion it will cause _____ ?

A

massive INTRAVASCULR haemolysis and this is

potentially fatal

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3
Q

Blood test reveal an individual has A and B antibodies (Anti-A, Anti-B) present in the blood. what blood group are they?

A

Group O

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4
Q

Blood test reveal an individual has A antibodies (Anti-A, ) present in the blood. what blood group are they?

A

Group B

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5
Q

Blood test reveal an individual has no antigens present in the blood. what blood group are they?

A

Group O

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6
Q

85% of population are which rhesus group?

what does this mean for transfusions?

A

Rh +ve

Carry the RhD antigen

Patients can receive RhD negative (just a waste!)

Just give them RhD positive red cells because they can receive it!

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7
Q

True/False:

Immune anti-D antibodies cause direct agglutination of RBCs

A

False

they DO NOT

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8
Q

what are Immune anti-D antibodies notorious for?

A

Causing delayed haemolytic transfusion reaction:

form an antibody: antigen complex with the transfused red cells and this results in EXTRAVASCULAR HAEMOLYSIS in the spleen

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9
Q

Immune anti-D antibodies are what type of antibody?

A

Are IgG (so cross the placenta)

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10
Q

true/false

in emergency situations, you can use RhD-positive blood for the transfusion of RhD-negative patients

A

True

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11
Q

what are the risks of using RhD-positive blood for the transfusion of RhD-negative patients?

what does this mean for future transfusions

A

this does not cause acute problems
sometimes induces formation of anti-D*

will be picked up by the lab next time they need blood.

future transfusions:
RhD-negative blood would then be issued.

*especially an issue in pregnant women

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12
Q

In column agglutination tests , what do the following mean:

Agglutination (clumping)
Red cells stay suspended

A

Positive :
Agglutination (clumping)

Negative :
Red cells stay suspended

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13
Q

In column agglutination tests,
a patient has agglutination with Anti-A and anti-D and B cells.

No reaction with Anti-B or A cells

what does this mean?

A

They are blood group: A RhD +ve

had reaction with B RBCs (in reverse group testing) because group A will have Anti-B antibodies. these will react/agglutinate to B antigens, which the B RBCs will have.

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14
Q

reverse group is used to test for what?

A

checks blood group via reverse technique

checking antibodies - Anti-A or Anti-B already in the plasma

NOT checking for Immune antibodies

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15
Q

A woman is in labour and requires a blood transfusion. She had her blood group and group and screen done at booking. how do we proceed now?

A

Do another Group and Screen/save first

BLOOD GROUP is done before every transfusion, even if it has been done many times before

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16
Q

Immune RBC antibodies are _____?

ABO antibodies are ___

Rh antibodies are ___

A

IgG

IgM

IgG

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17
Q

How and when do we screen for antibodies in patient blood? what are the details?

A

using the INDIRECT ANTIGLOBULIN TECHNIQUE

ANTIBODY SCREEN is done before every transfusion

Checks for presence of immune antibodies eg made upon rhesus sensitisation (not normal anti-a/anti-b ones)

Uses anti-human IgG

+ve = clumping

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18
Q

donor RBCs are labelled with ___?

A

ABO & D TYPE
Kell
OTHER Rh ANTIGENS

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19
Q

what kell type should be given to women and why?

A

We give K-negative blood to women of childbearing potential because anti-K can cause HDFN.

85-90% of the population is K-negative - Hemolytic disease of the fetus and newborn

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20
Q

what is involved in a Serological Crossmatch?

A

donor cells were mixed with the patient’s plasma and incubated at 37C and then an antiglobulin reagent

agglutination/haemolysis = not compatible

not suitable in an emergency.

Another way is to mix donor cells and patients plasma in the same way but at room temperature and without incubation.

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21
Q

what negates the need for Serological Crossmatch after ABO and Rh testing?

A

ELECTRONIC ‘CROSSMATCH’ - done electronically

because usually ABO n Rh testing is insufficient, yuo have to check serology etc

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22
Q

how are red cells stored?

A

Stored at 40 C for 35 days.

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23
Q

how are red cells given / transfused

A

Transfuse 1 unit RBC over 2-3 hours

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24
Q

how are platelets stored and given?

issues?

A

Stored at 20 0 C for 7days

  • storing at room temp = risk of bacterial infections though rare

Transfuse 1 unit of platelets over 20-30 minutes

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25
Q

what compatibility is required to give platelets?

A

Should be Rh D compatible

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26
Q

what compatibility is required to give FFP & Cryoprecipitate ?

A

Give ABO compatible but D group does not matter

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27
Q

what is Maximum Surgical Blood Ordering Schedule (MSBOS)?

A

is based agreement between surgeons and transfusion lab about
predictable blood loss for ‘routine’ planned surgery.

helps them know how much blood might bee needed based on which type of surgery

28
Q

what are the 2 routes of MSBOS in ELECTIVE SURGERY?

A
  1. GROUP AND SCREEN
    - if no antibodies present -> put in fridge
    - then issue blood by electronic issue
  2. CROSSMATCH
    - must do this if antibodies present or prev reaction
    - identifying which antibody is present to give antigen negative blood
29
Q

what are the indications and thresholds for transfusion ?

A

Major Blood Loss
- if >30% Blood volume lost

Peri-Op, Critical Care
- Hb <70g/L vs 80g/L

Post Chemo
- Hb <80g/L

Symptomatic anaemia – ischaemic heart disease, breathless, ECG changes

30
Q

1 unit RBC gives a Hb increment of — ?

A

10g/L in a 70-80 kg patient

31
Q

Transfusion to above ____- is rarely required, unless symptomatic or severe cardiac/respiratory disease etc.

A

100g/L

32
Q

what are the indications for platelet transfusion?

A

Massive transfusion
Aim Plts >75 x109/L

Prevent bleeding (post chemo)
If < 10 x109/L (<20 if sepsis)
Prevent bleeding (surgery) - keep platelet above these figures:
< 50 x109/L (<100 if critical site: eye, CNS, polytrauma)

Platelet dysfunction or immune cause – only if active bleeding

33
Q

what are the contra-indications for platelet transfusion?

A

Heparin-induced Thrombocytopenia Thrombosis (HiTT)

Thrombotic Thrombocytopenic Purpura (TTP)

34
Q

One unit of platelets is an adult treatment dose: usually raises platelet count by ____ ?

A

30-40 x109/L

35
Q

What are the indications for FFP? dosage?

A

Replacement of single coagulation factor deficiency, e.g. factor V.

DIC - if patient is bleeding and abnormal coagulation results.

Thrombotic thrombocytopenic purpura (TTP)

Massive transfusion

dosage - 4 units in 70kg man

36
Q

what does cryoprecipitate contain?

A 
Fibrinogen
vWF & FVIII
FXIII
Fibronectin
IgA
Albumin
Platelet Microparticles
37
Q

when are these special types of blood indicated:

CMV negative blood -
Irradiated blood -
Washed -

A

CMV negative blood - only required for intra-uterine /neonatal transfusions and for elective transfusion in pregnant women (baby in-utero is exposed to maternal transfusion)

Irradiated blood - required for highly immunosuppressed patients, who cannot destroy incoming donor lymphocytes: which can cause (fatal) transfusion associated graft versus host disease (TA-GvHD)

Washed - red cells and platelets are only given to patients who have severe allergic reactions to some donors’ plasma proteins

38
Q

what is the ABO Frequency in Donors from most to least common?

A

O -> A -> B -> AB

Rh positive is always more common than negative
so O positiive i most common 33%

39
Q

what are the 2 ways Red cells are cross matched ?

A

serologically or electronically

40
Q

what are the acute <24hrs ADVERSE REACTIONS TO TRANSFUSION?

A 
Acute haemolytic (ABO incompatible)
Allergic/anaphylaxis

Infection (bacterial)
Febrile non-haemolytic

Respiratory

  • Transfusion associated circulatory overload (TACO)
  • Acute lung injury (TRALI)
41
Q

what are the delayed >24hrs ADVERSE REACTIONS TO TRANSFUSION?

A

Delayed haemolytic transfusion reaction (antibodies)
Infection
viral - HIV, CMV, HBV, HCV, Parvovirus
malaria, vCJD

TA-GvHD
Post transfusion purpura
Iron overload

42
Q

what would an ACUTE REACTION to transfusion look like?

A

rise in temp or pulse
or fall in BP

Fever, rigors, flushing, vomiting, dyspnoea, pain at transfusion site, loin pain/ chest pain, urticaria, itching, headache, collapse etc

43
Q

how does a FEBRILE NON-HAEMOLYTIC TRANSFUSION REACTION (FNHTR) present, cause and how is it treated?

A

‘MILD/MODERATE’ reaction

During / soon after transfusion (blood or platelets),
Fever- rise in temperature of 10C, chills, rigors

Common before blood was leucodepleted, now rarer

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

Cause: White cells can release cytokines during storage

44
Q

how does an ALLERGIC TRANSFUSION REACTION present, cause, and how is it treated?

A

‘MILD/MODERATE’ reaction

Common especially with plasma
Mild urticarial or itchy rash sometimes with a wheeze
During or after transfusion

Usually have to stop or slow transfusion
IV antihistamines to treat (and prevent in future if recurrent)

Cause:
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

45
Q

what is the consequences of giving the wrong blood?

how is it treated?

A

‘severe or fatal’ reaction

Symptoms and signs of acute intravascular haemolysis- IgM

Restless, chest/ loin pain, fever, vomiting, flushing, collapse, haemoglobinuria (later);
↓BP & ↑HR (shock), ↑Temp

Stop transfusion – check patient / component
Take samples for FBC, biochemistry, coagulation,
Repeat x-match and Direct Antiglobulin Test (DAT)
Discuss with haematology doctor ASAP

46
Q

what are the categories of reasons why transfusoin reactions occur?

A

Errors - 84%
Anti-D, handling errors

Not preventable occurrences - 10%
eg allergic reactions

Possibly preventable occurrences - 5%
eg TACO, haemolytic rxns

47
Q

bacterial infections are most common in which transfusion types in order and why?

A

Platelets >red cells > frozen components (storage temp)

48
Q

how can bacterial contamination of blood products occur?

how does it present in the recipient?

A

From the donor (low grade GI, dental, skin infection)
Introduced during processing (environmental or skin)

presentation: similar to that of receiving wrong blood:

Restless, fever, vomiting, flushing, collapse.

↓BP & ↑HR (shock), ↑Temp

49
Q

transfusion related anaphylaxis occurs how?

A

immediate reaction

50
Q

what are the
RESPIRATORY COMPLICATIONS OF TRANSFUSION ?

which is the most common pulmonary complication?

A

Transfusion Associated Circulatory Overload (TACO) - most common

Transfusion Related Acute Lung Injury (TRALI)
Transfusion Associated Dyspnoea (TAD)

51
Q

How does TACO present and what are the clnical features. and ivx?

A

Pulmonary oedema / fluid overload;
Often lack of attention to fluid balance, especially in cardiac failure, renal impairment, hypo-albuminaemia, those on fluid replacement, very young, very small eg weight <50kg and very old.

Clinical features: SOB, ↓SAO2 , ↑HR, ↑BP
CXR: fluid overload / cardiac failure

52
Q

what is the TACO checklist?

A

the list of conditions that patients are assessed for prior to transfusion to determine risk of TACO

if yes to anything on list - transfuse 1 unit - reassess anaemia. consdider not transfusing. consider prophylactic diuretics etc

53
Q

whats the difference between TRANSFUSION RELATED ACUTE LUNG INJURY (TRALI) and TACO on ivix?

A

TRALI:

CXR: bilateral pulmonary infiltrates during/within 6 hr of transfusion, not due to circulatory overload or other likely causes

54
Q

what is the MOA behind 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

55
Q

when do infections present post transfusion?

A

months - years

56
Q

CMV infection can be fatal in which individuals? solution?

A

Very immunosuppressed (stem cell transplant) patients can get fatal CMV disease,

but leucodepletion removes CMV (in wbc’s)

57
Q

parvovirus infection is a worry in which patients?

A

foetuses and patients with haemolytic anaemias e.g. sickle cell; hereditary spherocytosis

58
Q

what is the MOA behind DELAYED HAEMOLYTIC TRANSFUSION REACTION?

A

develop an ‘immune’ antibody to a RBC antigen they lack
ALLOMMUNISATION

If the patient has another transfusion with RBCs expressing the same antigen, antibodies cause RBC destruction. EXTRAVASCULAR HAEMOLYSIS (as IgG) so takes 5-10 days

59
Q

what results would be seen on ivx

A

Increased:
Bilirubin
LDH
Retics

Decreased:
Hb

DAT (positive)
Haemoglobinuria over few days
Test U&Es – as can cause renal failure

60
Q

what is the prognosis of Transfusion Associated Graft-Versus-Host Disease (TaGVHD)?

A

Rare but ALWAYS fatal - WEEKS -> MONTHS

61
Q

what is the cause of Transfusion Associated Graft-Versus-Host Disease (TaGVHD)

presentation?
prevention?

A

Cause:
Donor Lymphocytes recognise patient’s tissue HLA antigens as ‘foreign’ – so attack patient’s gut, liver, skin and bone marrow

presentation:
severe diarrhoea, liver failure, skin desquamation,
bone marrow failure

prevention:
irradiate blood components for very immunosuppressed; or patients having HLA matched components

62
Q

what is the threshold for iron chelation?

A

once ferritin >1000

63
Q

how is Post Transfusion Purpura treated?

aetiology?

A

infusion of IVIG

aetiology: Low platelets in HPA -1a negative patients

64
Q

when can you start doing kleihaeur test for FMH?

before then?

A

(Kleihauer test) is always done if > 20 weeks pregnant

before this:
250 iu - for events before 20 weeks of pregnancy

65
Q

what is the Mechanism of action of prophylactic anti-D Immunoglobulin?

A

RhD positive (foetal) red cells get coated with anti-D Ig and then they get removed by the mother’s reticulo-endothelial system (spleen) before they can sensitise the mother to produce anti-D antibodies

Path - Immuno (11 decks)

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