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Blood > Haem 11 > Flashcards

Haem 11 Flashcards

1
Q

Where is blood from for donation

A

Human source - no synthetics yet (research) - not risk free

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2
Q

When is blood used

A

When no safer alternative

If massive bleeding - if ‘plain fluids’ not sufficient

If anaemic - if iron/ B12/ folate not appropriate

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3
Q

Outline the basis of blood group

A

All have common H antigen:

A has galnac added on
B has gal added on

AB has some with either, O just has H stem

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4
Q

What are antigens determined by

A

Antigens determined by corresponding genes

A gene codes for enzyme which adds N-acetyl galactosamine to common glycoprotein and fucose stem

B gene codes for enzyme which adds galactose

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5
Q

Inheritence of O

A

It is receissive, so must have 2 O groups if you are blood group O

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6
Q

Possible blood group for A

A

AA, or OA

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7
Q

Which antibodies do you have against antigens

A

Person has antibodies against any antigen NOT present on own red cells

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8
Q

What type of antibody is made against the blood cell antigens that you do not have

A

Naturally occurring (nearly from birth) - IgM: it is a ‘complete’ antibody, so:- fully activates complement cascade to cause haemolysis of red cells

(pentameric so it cross links, activates complemet, and causes MAC and punches holes in the red cell membranes, and cytokine storms)

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9
Q

Group A given to group O patient

A

blood group A given to patient who is group O - so has anti-A and anti-B - then antibody/ antigen interaction often fatal

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10
Q

What i shown in tests to determine blood group

A

In laboratory tests, IgM Abs interact with corresponding ag to cause agglutination eg: if patient is group B, he has anti-A antibody in plasma - when add to group A cells - agglutination seen (clump) - shows cells are incompatible

How is ABO blood group determined (slide 9)

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11
Q

Commonest blood group in UK

A

O, A, B and AB

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12
Q

Which antibodies for each blood group

A

A: anti B
B: Anti A
O: Anti A and Anti B
AB: none

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13
Q

What is the Cross match

A

Final check, adding patient’s plasma to the blood you are going to transfuse to ensure it doesnt agglutinate

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14
Q

What types of RH groups

A

RhD is most important

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15
Q

What are the types of RhD groups

A

RhD positive or RhD negative

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16
Q

What are the potential genotypes for RhD positive and RhD negative

A

RhD +ve: DD or Dd

RhD -ve: dd

Most RhD positive in UK

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17
Q

How are antibodies made against RhD in RhD negative people

A

RhD-ve people CAN make anti-D antibodies AFTER they are exposed to the RhD antigen - either by transfusion of RhD positive blood or in women, if they are pregnant with an RhD positive fetus

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18
Q

What type of antibodies made against RhD antigens

A

IgG antibodies

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19
Q

What is the consequence of IgG coating of the RhD antien

A

Not MAC, but complex recognised by spleen, and has membrane pinched out, leading to spherocytes and then are taken out second time around… causes delayed haemolytic transfusion reaction - anaemia; high bilirubin; jaundice etc

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20
Q

Implications of anti-D antibodies (antibodies aginst RhD postiive)

A
  1. Future transfusions
  2. Haemolytic disease of the newborn (HDN)…
    if RhD neg mother has anti-D - and in next pregnancy, fetus is RhD pos - mother’s IgG anti-D antibodies can cross placenta - causes haemolysis of fetal red cells - if severe: hydrops fetalis; death
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21
Q

Why isn’t RhD neg given to RhD positive people

A

no harm to give RhD neg to a pos patient - just wasteful

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22
Q

What blood group can be used for everyone

A

O neg used as emergency blood when patient’s blood group not known (NB only 6-7% of donors are O neg)
….

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23
Q

What other antigens can be present on red cells, do they matter

A

Don’t routinely match blood for all these, eg Rh group -C, c, E, e; others - Kell, Duffy, Kidd, etc

about 8% of patients transfused will form antibody to one or more of these antigens…..

It is important….
Once have formed antibody must use corresponding antigen negative blood; or else risk of delayed haemolytic reaction (can be severe)

24
Q

What is done to avoid the delayed haemolysis associated with these other antibodues

A

as well as testing their ABO and RhD group BEFORE each transfusion episode, test patient’s blood sample for red cell antibodies

you need to do a new one each time

25
Q

Questions on slide 16

A

Cannot be AB or O

26
Q

Components of blood

How much is collected from each donor

Why is blood not kept as whole blood

Why is red cells + plasma not given to patients needing RBC

What layers appear after centrifugation of blood

A

1 unit (‘pint’) blood collected into a bag containing anticoagulant

Whole blood not given:

  • more efficient, less waste
  • some components degenerate if stored as whole blood

Red cells – concentrated, as plasma
removed; also avoids fluid overloading patients

Split one unit of blood by centrifuging whole bag (red cells bottom, platelets + leukocytes middle (=buffy coat), plasma top) then squeeze each layer into satellite bags and cut free (closed system)

27
Q

What can whole blood be used to make

A
  1. Red cells
  2. Platelets
  3. Plasma
28
Q

Why would you use cryoprecipitate

A

it’s fibrinogen rich

29
Q

What can you do with plasma

A

-into fresh frozen plasma (FFP) or cryopreciptate, or plasma for fractionation, in which you pool thousands…

30
Q

What can plasma for fractionation be used for

A

Can take out albumin, factor VIII, IX immunoglobulins, anti-D etc.

31
Q

Shelf life of the red cells

A

Shelf life 5 weeks; stored at 4oC (fridge)

1 unit from 1 donor - ‘packed cells’ (fluid plasma removed)

32
Q

How are red cells given

A

Give through a ‘blood giving set’ - has filter to remove clumps/debris

33
Q

What are frozen red cells needed for

A

for rare groups/ antibodies - poor recovery on thawing, rare… but you lose some red blood cells

34
Q

Fresh frozen plasma how much from each donor

A

1 unit from 1 donor (300ml) can get small packs for children

35
Q

How is FFP stores and shelf life

A

Stored at -30oC (frozen within 6h of donation to preserve coag factors)

Must thaw approx 20-30 mins before use (if too hot, proteins cook)

36
Q

What dose of FFP needed

A

Dose 12-15ml/kg = usually 3 units

37
Q

What is needed to match FFP

A

Need to know blood group - no x-match, just choose same group (as contains ABO antibodies from donor, which could cause a bit of haemolysis with receipient cells

38
Q

When is FFP needed

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= Prothrombin complex concentrate, also known as factor IX complex, is a medication made up of blood clotting factors II, IX, and X. Some versions also contain factor VII. It is used to treat and prevent bleeding in hemophilia B if pure factor IX is not available.. )
  3. Other conditions occasionally
39
Q

Cryoprecipitate storage

A

Same as FFP - store at -30oC for 2 yrs

40
Q

Standard cryoprecipitate dose

A

Standard dose = from 10 donors (can split into 5 in each pack and give two bags)

41
Q

Important feature of cryoprecipitate

A

Contains fibrinogen and factor VIII

42
Q

Indication for cryoprecipiate

A

If massive bleeding and fibrinogen very low

Rarely hypofibrinogenaemia

43
Q

How many donors needed for a pool of platelets

A

4 donors

or from 1 donor by apheresis (cell separator machine)

44
Q

Shelf life of platelets

A

Shelf life 5 days only - (risk of bacterial infection)

45
Q

What info is needed for platelet

A

Blood group:

No cross-match, just choose same group (as platelets have low levels of ABO antigens on, so wrong group platelets would be destroyed quickly) - and can cause RhD sensitisation, as some red cell contamination

46
Q

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

47
Q

How much plateltet is needed usually

A

1 pool

48
Q

Which cotting factors affected by warfarin

A

2, 7, 9 and 10

49
Q

How does fractionated plasma work

A

Fractionated (like oil)

50
Q

What can be gleaned from fractionated plasma ..

A

Factor VIII and IX,

Immunoglobulins and albumin

51
Q

When is factor VIII and IX needed from fractionated products

A

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

52
Q

When are immunoglobulins needed from 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

53
Q

When is albumin needed and at what dose

A

4.5%
Useful in burns, plasma exchanges, etc
Probably overused (not indicated in malnutrition)
20% (salt poor)
For certain severe liver and kidney conditions only

54
Q

WHat does cross matching involve

A

X-match: patient’s serum mixed with donor red cells - should not react

55
Q

WHat proportion of people have RhD negative and which proportion RhD positive blood

A

85% of people are RhD positive; 15% are RhD negative

Blood (12 decks)

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