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Year 2 - MCD Haem > Blood Transfusions > Flashcards

Blood Transfusions Flashcards

1
Q

What is our only source for blood and what is important about it?

A

Humans!

NO synthetic source yet that is risk-free

It is a SCARCE resource so needs to be used carefully

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2
Q

When is blood transfusion normally used?

A

Only use when NO other safer alternative is available
e.g. massive bleeding - ‘plain fluids’ not enough
anaemia - iron/B12/folate not appropriate

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3
Q

What is the most important of all blood groups?

A

ABO blood groups

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4
Q

Describe the ABO blood groups

A
  1. Groups A & B have an EXTRA SUGAR RESIDUE attached (to the common glycoprotein & fructose stem)

o ‘A’ gene codes for N-acetyl galactosamine
o ‘B’ gene codes for galactose

  1. Group O has NO EXTRA SUGAR

o just the fructose stem

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5
Q

What is unique about the ‘A’ , ‘B’ and O genes?

A

‘A’ & ‘B’ genes are CO-DOMINANT

O gene is RECESSIVE

i.e. Blood group A - genes could be AA or OA

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6
Q

Which blood group is the universal DONOR?

A

OO-

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7
Q

Which blood group is the universal RECIEVER?

A

AB+

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8
Q

Why are ABO Group antigens and Abs so important?

A

Person has Abs AGAINST any antigen NOT present on own RBC

i.e. patient w. Group A will have Abs AGAINST Group B blood

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9
Q

Which Ab reacts against mis-matched blood?

A

IgM

A 'complete' Ab so if activated:
 o causes a COMPLETE complement cascade
 o haemolysis of RBCs
 o Agglutination of RBCs
 o FATAL!
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10
Q

Antigens and Abs for Blood Group A?

A

Blood Group - A

Antigens of RBCs - A

Abs in plasma - Anti-B

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11
Q

Antigens and Abs for Blood Group B?

A

Blood group - B

Antigens of RBCs - B

Abs in plasma - Anti-A

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12
Q

Antigens and Abs for Blood Group O?

A

Blood group - O

Antigens of RBCs - N/A (so can be donor!)

Abs in plasma - Anti-A & anti-B

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13
Q

Antigens and Abs for Blood Group AB?

A

Blood group - AB

Antigens of RBCs - A & B

Abs in plasma - N/A (so can receive any!)

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14
Q

How are blood groups tested for matching?

A

Patient’s blood tested by reacting it with known anti-A & anti-B reagents

A donor is then selected
The blood is cross-matched to be sure (x-match) - check for agglutination

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15
Q

RH blood groups?

A

RhD is the most important!

RhD+ = have D-antigen (on RBC)
RhD- = NO D-antigen (on RBC)
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16
Q

Genetic profile of RhD gene?

A

Co-dominant!

e.g. dd = NO D-antigen
Dd/DD = D-antigen present

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17
Q

% of people in each blood group?

A

A - 42%
B - 8%
O - 47%
AB - 47%

85% are RhD+
15% are RhD-

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18
Q

How are blood grouped named?

A

Usually shortened

i. e. ABO (ABO blood group) +/- (RhD status)
e. g. AB+ (AB blood group) (RhD+)

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19
Q

What can happen to RhD- people however?

A

Can make D-Abs AFTER exposure to RhD antigen!

i.e. by transfusion of RhD+ blood OR in women if pregnant with RhD+ child

20
Q

What is different about anti-D Abs in comparison to the ABO Abs?

A

It is IgG Abs!

SO not as bad as IgM

21
Q

Antigens and Abs for RhD+?

A

Antigen = D +

Abs = N/A

22
Q

Antigens and Abs for RhD-?

A

Antigen = N/A

Abs = CAN make anti-D if sensitised

23
Q

What are the implications for RH blood groups due to the possibility of anti-B sensitisation?

A
  1. Future transfusions

After receiving a RhD+ transfusion (if patient is RhD-):
o patient MUST have RhD- blood
OTHERWISE
the anti-D Abs they had made from the first transfusion would react!

Would cause DELAYED HAEMOLYTIC TRANSFUSION REACTION causing anaemia, high bilirubin, jaundice etc.

  1. HDN - haemolytic disease of the newborn

RhD- mother had anti-D Abs made post-transfusion
o then if in her NEXT pregnancy has a child that is RhD+, the mothers IgG Abs will cross the placenta and attack the child’s RBCs

24
Q

What is important about RhD Group in terms of anti-D Abs?

A

AVOID RhD- patients making anti-D Abs

25
Q

How can you avoid the issue w. RhD group and anti-D Abs?

A
  1. Transfuse blood of the same RhD Group as the patient

o Remember - can give RhD- to ANY patient as no antigens!

  1. O- blood is used in an emergency

o as it CANNOT react with any combination in the patient (no antigens!)

26
Q

What are the other blood groups?

A

Other antigens on RBCs that we DO NOT routinely match

e.g. RhC, c, E, e and others e.g. Kell, Duffy, Kidd

27
Q

What is a risk regarding the other blood groups?

A

About 8% of patients transfused form Abs to the other blood group antigens!

So once the patient has formed these Ab, must use corresponding antigen -ve blood
OR
risk of delayed haemolytic reaction

28
Q

How do we know if a patient will need antigen -ve blood?

A

BEFORE each transfusion, test the patient’s blood sample for RBC Abs

Therefore, as well as testing their ABO and RhD groups, must also do an:

ANTIBODY SCREEN of their plasma

29
Q

A woman is O positive; her partner is AB positive. Which of these cannot be a child of theirs?

A

AB+

&

O+

30
Q

A patient is B positive. Which of the following blood could kill them?
A positive
O positive
B negative

A

A+

31
Q

How is blood given to a patient and why?

A

Give patients what they need of the component of blood - this is to:

o stop waste
o certain components degenerate quickly is stored as whole blood
o NOT fluid overload patients

SO centrifuge the blood to form:
o TOP = plasma
o MIDDLE = platelets
o BOTTOM = RBCs

32
Q

Characteristics of RBCs?

A

1 unit/donor

o stores for 5 weeks at 4oC
o given via blood giving set - has filter to remove clumps/debris

o NOT normally given frozen (only for rare groups)
- as poor recovery upon thawing

33
Q

FFP?

A

Fresh frozen plasma

34
Q

Characteristics of FFP?

A

1 unit/donor (dose is 3 units)

o store for 2years at -30oC

  • thaw 20-30mins before use (give ASAP or coag factors degenerate at room temp)
  • NO x-matching needed BUT need blood group (as contains ABO Abs so could cause haemolysis)
35
Q

What are some indications when FFP needs to be used?

A

Need to use:

  1. If BLEEDING & abnormal coag test results (PT, APTT)
    o monitor response clinically & w. coag tests
  2. Reverse effect of Warfarin (anticoagulant)
    o e.g. for urgent surgery (if PCC not available - prothrombin complex concentrates)
36
Q

Cyroprecipitate?

A

Formed from FFP thaw residue! (1 dose from 10 donors)

Stored at -30oc for 2 years

Contains
 o Fibrinogen
 o F8
SO
given for massive bleeding & very low fibrinogen (rarely for hypofibrinogenaemia)
37
Q

How is platelets given as blood donation?

A

1 pool from 4 donors
OR
1 donor by apheresis (cell separator machine)

Stored at 22oC (but constantly agitated) for 5 days only as risk of bacterial infection!

Need to be given in plasma suspension as if not, platelets would agglutinate

38
Q

What do you need to know before giving platelets?

A

Blood-group BUT x-match NOT necessary

Platelets have LOW LEVELS of ABO antigens
SO
wrong platelet group would be destroyed quickly

Can cause RhD sensitisation however as some RBC contamination

39
Q

What are some indications when platelets needs to be used?

A

o Bone marrow failure
o massive bleeding (or DIC)
o surgery (patient has LOW platelet levels)
o Cardiac bypass (patient on anti-platelet drugs)

40
Q

If a patient is bleeding post surgery, what components does he need if:

a) His platelet count is normal and his coagulation test (PT and APTT) are prolonged?
b) His PT and APTT are long and his fibrinogen is low?

A

A - needs FFP

Because his PT and APTT are both prolonged suggesting that there are problems in the EXTRINSIC & INTRINSIC pathways
SO
MORE THAN ONE factor is missing

B - need FFP & Cryoprecipitate

Cryoprecipitate only has fibrinogen & F8 and so will solve the low fibrinogen problem
BUT
the FFP will supplement the other coagulation factors

41
Q

What are fractioned products?

A

Taken from a large pool (1000s) of donors, mixed and fractioned off (like oil)

42
Q

What are potential products from Fractioned products?

A
  1. F8 and F9

o for haemophilia A & B
AND
o F8 for vWD

  • It is heat treated to inactivate viruses
  • Recombinant F8 and F9 alternatives increasingly used but £££
  1. Igs (to treat specific illnesses)

o IM-Ig - specific e.g. tetanus, anti-D, rabies
o IM-Ig - normal globulin (broad mix in population e.g. HAV)
o IV-Ig - Pre-op patients with ITP or AIHA (autoimmune haemolytic anaemia)

  1. Albumin

o 4.5% - for burns, plasma exchange etc.
o 20% - severe liver & kidney conditions

43
Q

Protocol in place for donors?

A
  1. Blood kept safe for patient by
    o testing for infections
    o exclusion of donots by a questionnaire
  2. Donors also kept safe by
    o exclusion of risky donors e.g. if have heart problems
44
Q

Infection that all blood bust be tested for?

A

Includes:

o Hep B and C
o HIV
o HLTV (Human T-lymphocyte Virus)
o Suphilis
o CMV or HEV
45
Q

Impact of ‘window period’ and donors?

A

‘Window period’ of infections!

When levels are TOO LOW to detect in system so will go by undetected

SO cannot only rely on testing

46
Q

Some infections could also be transmitted via. blood transfusion - include?

A

Prion disease - VCJD

As a precaution, all plasma pooled to make fractioned products is obtained from USA (UK plasma used for FFP, rest thrown away)

AND

all blood components have WBCs filtered out (WBC essential for uptake of vCJD prion into brain)

Year 2 - MCD Haem (11 decks)

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