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I need to learen > Blood Transfusion > Flashcards

Blood Transfusion Flashcards

1
Q

What are the sources of blood donations

A

Human

1 donor - 1 pint of blood every 4 months

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2
Q

When are blood donations used

A

When there is no safer alternative
e.g. Massive bleeding - plain fluid not sufficient
Anaemia - iron/B12/folate not appropriate

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3
Q

Describe molecular structure of the ABO blood groups

A

A and B antigens on red cells are formed by adding 1 or other sugar residue onto a common glycoprotein and fucose stem

Group O has neither A or B sugars (stem only)

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4
Q

Describe the genetics of the ABO blood groups

A

Antigens determined by corresponding genes
A-gene codes for enzyme which adds N-actyl galactosamine to common glycoprotein and fucose stem
B genes - enzyme adds galactose
A + B = co-dominant
O = recessive

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5
Q

Describe the antibodies against ABO antigens

A

Antibodies present for antigens not in the body

IgM is natural and activates fully the complement cascade for haemolysis of red cells

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6
Q

How is IgM used for cross matching

A

IgM antibodies interact with the corresponding antibodies -> agglutination
e.g. B has antibody A, so added to group A there will be clumping = incompatible

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7
Q

What are the proportions of ABO groups in the UK population

A

A - 42%
B - 8%
O - 47%
AB - 3%

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8
Q

Which antibodies are found in the plasma for the ABO groups

A

A - anti-B
B - anti-A
O - anti-B, anti-A
AB - none

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9
Q

What are the steps of finding a blood donor that matches the patient

A
  1. Patient blood sample (plasma + cells)
  2. ABO group (test with anti-A and B)
  3. Select donor unit of the same group
  4. Cross match - patient’s serum mixed with donor cells
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10
Q

Which RH group is most important and what are the types of this

A 
RhD 
RhD positive (D antigen) or RhD negative
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11
Q

What are the genes for RhD groups

A

D - codes for D antigen on RC membrane

d - codes for no antigens and is recessive

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12
Q

What proportion of the UK population are RhD positive

A

85%

15% negative

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13
Q

Describe the RhD antibodies

A

Those who lack RhD antigen can make anti-D antibodies after exposure to the antigen (transfusion or pregnancy with RhD positive foetus)
Anti-D antibodies = IgG

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14
Q

What are the implications of anti-D antibodies

A

Patient must have RhD -ve blood (otherwise anaemia, high bilirubin, jaundice)

Haemolytic disease of the newborn

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15
Q

Describe haemolytic disease of the newborn (HRN)

A

RhD -ve mother (anti-D), foetus is RhD +ve, mother’s IgG anti-D antibodies cross the placenta and causes severe haemolysis of fatal red cells

Severe - hydros fetalis, death

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16
Q

What is important in the treatment of RhD group patients

A

Avoid RhD -ve patients from making anti-D

- transfuse blood of the same RHD group

17
Q

Describe the other red cell groups (other than ABO, RhD)

A

C,c,E,e
Kell, Duffy, Kidd
8% of its transfused will form Ab to one or more of these antigens

18
Q

How do we know if the patient needs antigen negative blood

A

Before each transfusion episode the patient’s blood sample is tested for Ab
Therefore there is an antibody screen of plasma as well as ABO and RhD group testing

19
Q

Why would a patient need antigen negative blood

A

Patients who form Ab to other cell group antigens

Corresponding antigen-negative blood needed to reduce risk of delayed haemolytic reaction

20
Q

How is blood prepared from donation

A

Collected in a bag with anticoagulant
Red cells become concentrated as the plasma is removed (avoids overloading patients)
Centrifuge the whole bag for red cells to fall to the bottom, platelets middle and plasma top

21
Q

What are the advantages of not giving whole blood to patients

A

More efficient - less waste as patients do not need all the components
Some components degenerate quickly is stored as whole blood

22
Q

What are the 3 forms of plasma from blood donation

A

Fresh frozen plasma
Cryoprecipitate
Plasma for fractionation (not UK) -> albumin

23
Q

Describe the red cell component of blood donation

A

Plasma removed
Shelf life of 5 weeks at 4 degrees
Blood giving set used - filters clumps and debris
Rarely frozen cells needed

24
Q

Describe the fresh frozen plasma

A 
300ml = unit 
-30 degrees storage (frozen within 6hrs for coagulant factor preservation)
Shelf life 2 years
Thaw for 20-30 minutes 
12-15ml/kg dose (3 units)
Blood group is not required
25
Q

What are the indications for fresh frozen plasma

A
  1. If bleeding + abnormal coag test results (PT, APTT)
    • Monitor response - clinically and by coag tests
  2. Reversal of warfarin (anticoagulant) eg for urgent surgery (if PCC not available)
  3. Other conditions occasionally
26
Q

Describe cryoprecipitate

A

Made from frozen plasma thawed overnight
Contains fibrinogen and factor VIII
Stored at -30degrees for 2 years
Dose = 10 donors

27
Q

What are the indications of cryoprecipitate

A

If massive bleeding and fibrinogen very low

Rarely hypofibrinogenaemia

28
Q

Describe the platelet donation

A

1 pool = 4 donors
or 1 donor by aphaeresis
store at room temp. and constantly agitated
5 day shelf life (bacterial infection risk)
Blood group needed (no X-match)

29
Q

What are the indications for platelets

A

Mostly haematology patients with bone marrow failure (if platelets <10 x 109/L)
Massive bleeding or acute DIC
If very low platelets and patient needs surgery
If for cardiac bypass and patient on anti-platelet drugs

30
Q

What are the fractionated products

A

Factor VIII and IX

Immunoglobulins

31
Q

Describe the FVIII and FIX fractionated products

A

For haemophilia A and B (males)
Factor VIII for von Willebrand’s disease
Heat treated - viral inactivation
Recombinant factor VIII or IX alternatives increasingly used, but expensive

32
Q

Describe the immunoglobulin fractionated products

A

IM: Specific - tetanus; anti-D; rabies

IM: Normal globulin - broad mix in population (eg: HAV)

IVIg – pre-op in patients with ITP or AIHA

33
Q

When is albumin used

A

4.5% - burns, plasma exchange

20% - certain severe liver and kidney conditions

34
Q

How is blood from donors keep safe for the patient

A

Test for infection

Questioning for risk behaviour for exclusion

35
Q

Which infections are tested for in blood donors

A 
Hepatitis B 	- HBsAg, PCR
Hepatitis C	- anti-HCV, PCR             viruses
HIV		- anti-HIV, PCR
HTLV		- anti HTLV
Syphilis	- TPHA (spirochete)
Hepatitis E	- PCR
Some also tested for CMV (virus)
36
Q

Why can group O blood be given to anyone

A

No antigens present on the red cell (plasma taken away)

37
Q

Which blood group can be given when the blood type is unknown

A

O -ve used as emergency blood

38
Q

What is the PT and APTT test

A 
PT = prothrombin time 
APTT = activated partial thromboplastin time
39
Q

What is the significance of Variant Creutzfeldt–Jakob disease (vCJD) in blood transfusion

A

Can be transmitted by blood transfusion

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