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2A week 1 - anaemia, RBC metabolism etc. > the dilemmas of blood transfusion > Flashcards

the dilemmas of blood transfusion Flashcards

1
Q

what is a group and screen test

A

a blood group and antibody screen - conducted in the lab to identify a patient’s ABO and RhD blood group and then to screen the pt’s serum for antibodies against red blood cells

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2
Q

if a pt is blood group A what antibodies will they have in their serum

A

B antibodies

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3
Q

what does the serum screen look for

A

AB antibodies and non-AB antibodies -> there are 300 red cell antigens but only few are clinically significant

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4
Q

how long is the serum sample saved for after antibody screening

A

7 days

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5
Q

when are anti-A and anti-B antibodies produced and in response to what

A

produce in early childhood (18mo); in response to food antigens and bacteria in the environment

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6
Q

why is ABO incompatibility rarely a problem in pregnancy

A

Anti-A/B antibodies are IgM antibodies and so very large -> cannot cross the placenta

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7
Q

how do labs test for serum antibodies

A

by placing the serum in a centrifuge with RBCs of a known antigen and seeing whether agglutination occurs -> antibodies to the specific RBC will cause them to agglutinate, these will stay at the top of the sample as they are too big to spin down through the pores in the gel

i.e. type A RBCs are put in a serum with anti-A antibodies and so will agglutinate, this will not happen in a serum with anti-B antibodies only

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8
Q

blood groups and what antigens are on their RBC

A

group A - A
group B - B
group AB - A + B
group O - small H (too small to trigger antibody formation)

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9
Q

blood groups and what antibodies are present in their serum

A

group A - antiB
group B - antiA
group AB - none
group 0 - A + B

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10
Q

as well as ABO grouping, what is tested for in the blood grouping test

A

Rh D status - also tested for via centrifuge

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11
Q

what is cross-check and who is it not used in

A

a check using a reverse group which compares the pt’s blood against a known sample -> shows the pt’s serum contains expected antibodies

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12
Q

what is an electronic crossmatch/issue and what must be done prior to its use

A

the use of a computer to choose suitable units without performing a physical crossmatch in the lab as any unit of ABO + RhD compatible blood can be issued - done after further antibody screening against RBC panels with specific clinically important antigens

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13
Q

what is done if the RBC panel identifies agglutination with clinically significant antibodies

A

screen against a larger panel to pinpoint the antobody

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14
Q

in pts with RBC antibodies (clinically significant antibodies) what must be done before blood is issued to them

A

check there is no agglutination reaction in the lab between the pt’s serum and a small quantity of rbcs from the unit wanting to be transfused

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15
Q

how is safety ensured with blood transfusions? (3)

A

2 group and screen sample records required in the blood bank before ABO-matched blood can be issued; only correctly labeled samples accepted; barcodes and electronic pt identification checked against eachother

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16
Q

what is done in emergency transfusions situations where there are no/only one group and screen records

A

group O blood is given

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17
Q

what are examples of alternatives to blood transfusion (2)

A
  1. increasing RBC production using erythropeitin (EPO), anabolic steroids (e.g. danazol) - may also improve Hb;
  2. supporting haematopoesis with extra haemantinics (B12, folate, iron)
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18
Q

by how much does Hb typically rise with 1 unit of RBCs

A

10g/L

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19
Q

what else should be checked prior to transfusion and why

A

ferritin levels - prevent iron overload

20
Q

what components is whole blood split up into before it can be transfused

A

red cells; platelets; plasma; plasma derivatives (non-UK plasma source)
all blood is leucodepleted

21
Q

process of blood fractionation (6)

A
  1. blood is donated;
  2. blood tested for diseases e.g. HIV, Hep B, syphilis etc.
  3. filtered to remove leukocytes (leucodepletion);
  4. platelets removed by plateletpheresis
  5. fractionated into components -> red cells, pooled platelets, plasma + cyroprecipitate
  6. components stored for use
22
Q

how are the components of blood stored and how long is each one useable for

A

red cells: 4°C, 35 days;
platelets: 22°C kept in an agitator, 5 days;
plasma : -25°C, 36 months

23
Q

which blood component is usually given in an emergecny and why

A

red cells - they can be used straight away (no need for thawing)

24
Q

what should be considered if a massive red cell transfusion is given

A

pt bleeds out all components and so will need other components of blood too - esp platelets and plasma as this is an important source of clotting factors

25
Q

what may be triggered in a pt who is bleeding and unstable

A

massive blood loss protocol

26
Q

what is given by the blood bank in the massive blood loss protocol

A
  1. “packs” of fresh frozen plasma with red cells in set ratios;
  2. cryoprecipitate and platelets in the second pack if bleeding continues
27
Q

what will 1 unit of platelets raise the count by

A

20-30 x10^9/L (not normal level)

28
Q

do platelets need to be ABO/D identical?

A

no, but need to be compatible

29
Q

what is the universal plasma donor group and why

A

AB - there are no antibodies present

30
Q

why are people more susceptible to reacting to platelet transfusions

A

allergic reactions to plasma proteins; bacterial contamination (due to them being kept at room temp)

31
Q

what pts may need platelet transfusions

A

pts w a low count who need procedures; are bleeding; are having chemotherapy; thrombocytopenia due to bone marrow failure; abnormal platelet function; multifactorial thrombocytopaenia

32
Q

what does cryoprecipitate contain

A

concentrated levels of fibrinogen and factor VIII

33
Q

what is used in pts who need large amounts of plasma

A

octaplas -> inactivates any pathogens in large pools of plasma that are made from a large number of blood donors

34
Q

what factor deficiency is plasma transfusion still used for

A

rare conditions such as factor V

35
Q

on average how much plasma is given to a pt

A

3-4 pools; calculated by their weight

36
Q

when is fresh frozen plasma used (5)

A

DIC (disseminated intravascular coagulation) with bleeding; massive transfusion; plasma exchange in thrombotic thrombocytopenic purpura (octaplas); liver disease with abnormal clotting; rare factor deficiencies where factor concentrate is not available

37
Q

when might somone make antibodies for non-ABO or RhD antigens that they don’t express on their own red cells

A

after exposure during pregnancy or transfusion

38
Q

what is an alloantibody

A

immune antibodies that are only produced following exposure to foreign red blood cell antigens - IgG

39
Q

what time period must a group and screen sample be taken within to be used in someone who has had a transfusion or been pregnant in the last 3 months

A

72hrs

40
Q

what might occur if a pt if transfused w blood containing an antigen for a red cell antibody they have

A

delayed haemolytic transfusion

41
Q

consequences of IgG antibody mismatch in pregnancy

A

I gG antibodies are smaller and so can cross the placenta -> cause haemolyisis of fetal cells -> cause serious haemolytic disease of the fetus/newborn

42
Q

what can delayed haemolytic transfusion reactions cause (3)

A

jaundice; fever; poor haemoglobin rise

43
Q

what can cause transfusion reactions (3)

A

allergy to foreign plasma proteins; bacterial contamination; incompatible blood transfusion

44
Q

what can be used to raise Hb levels in renal impairment/myelodysplastic syndrome

A

erythropoeitin

45
Q

what drugs should be avoided in pts w thrombocytopenia and why

A

NSAIDs - impair the function of the remaining platelets

46
Q

What is haptoglobin

A

Binds to and transports free Hb

47
Q

Why do schistocytes form

A

RBI’s sliced by fibrin strands

2A week 1 - anaemia, RBC metabolism etc. (5 decks)

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