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Haematology > Transfusion > Flashcards

Transfusion Flashcards

1
Q

minimum criteria for being a blood donor?

A

haemoglobin
- 135 g/L in men
- 125 g/L in women
50kg weight

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2
Q

what happens to donated blood once received?

A

whole blood is centrifuged to separate into component parts

samples then undergo microbiological testing

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3
Q

what microbiological tests are done on donated blood?

A 
HIV
Hep B
Hep C
Hep E
HTLV
syphilis
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4
Q

how are blood components stored?

A

red cells = 4 degrees for 35 days
FFP = stored at -30 degrees for 3 years
platelets = stored at 22 degrees for 7 days with agitation

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5
Q

what products are available from transfusion labs

A 
blood components (red cells, FFP, platelets, cryoprecipitate)
blood products (anti-D, prothrombin complex concentrate)
blood products from pharmacy (IV Ig, human albumin, specific Ig)
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6
Q

what determines the blood type?

A

antigens on red cell surface

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7
Q

describe the ABO system of blood typing

A

found on chromosome 9

A and B genes encode for transferases which modify precursor called H substance on red cell membrane

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8
Q

how do A, B and O interact?

A

A and B are both dominant over O
and B are codominant
O is silent

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9
Q

which ABO types are most common?

A 
O = 47% 
A = 42%
B = 8%
AB = 3%
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10
Q

which antigens are present on red cell surface in each blood group?

A 
A = A antigens
B = B antigens
AB = A and B
O = neither
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11
Q

phenotype vs genotype?

A

phenotype = which antigens are detected
genotype = which genes are present
e.g
- phenotype = group O, genotype = OO
- phenotype = group A, genotype = AA or AO
- phenotype = group B, genotype = BB or BO
- phenotype = group AB, genotype = AB

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12
Q

how is ABO inherited?

A

one ABO gene from each parent

eg - mother = AO, father = BO - children can be AB, AO, BO or OO

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13
Q

what is Landsteiner’s law?

A

when an individual lacks the A or B antigen, the corresponding antibody is produced in their plasma
naturally occurring antibodies cause haemolysis of red cells expressing the specific antigen
this makes ABO the most clinically significant blood group system

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14
Q

which antibodies are present in each blood type?

A 
A = anti B
B = anti A
AB = neither
O = anti A and anti B
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15
Q

who can group O donate to/receive from?

A

can donate to everyone

can only receive from group O

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16
Q

who can group A donate to/receive from?

A

can donate to A

can receive from O and A

17
Q

who can group B donate to/receive from?

A

can donate to A and AB

can receive from B and O

18
Q

who can group AB donate to/receive from?

A

can donate to AB

can receive from all groups

19
Q

what is the 2nd most important antigen present on RBCs after A/B?

A

RhD

85% of people are RhD positive

20
Q

describe RhD antigens?

A 
2 alleles - D and d
- D is dominant, d is silent
inherit one from each parent
RhD +ve = DD or Dd
RhD -ve = dd
21
Q

clinical significance of RhD antigen?

A

very immunogenic
anti-D antibody can cause transfusion reactions and haemolytic disease of the newborn
should avoid exposing RhD negative people to D antigen through transfusion

22
Q

how can individuals be sensitised to exposure to foreign antigens?

A

pregnancy
transfusion
(repeat exposure may result in transfusion reaction)

23
Q

what are the aims of pre-transfusion testing?

A

identify ABO and RhD group of patient
identify presence of clinically significant red cell antibodies
allow selection of appropriate blood for transfusion

24
Q

how can ABO group be determined?

A

test patient’s red cells with anti-A, anti-B and anti-D antisera (identifies antigens on red cells via direct agglutination with IgM)
or
test patients plasma against reagent red cells of group A and group B (identifies antibodies in the plasma)

25
Q

how do antibodies and antigens on red cells interact?

A

cause agglutination

26
Q

how can antibody screening be done in blood?

A

test patient’s plasma against several reagent red cells which express a known range of antigens

  • identifies antibodies in the plasma
  • use the direct anti-globin test
27
Q

what is the indirect anti-globulin test?

A

addition of anti-human globulin (AHG) to plasma/red cell suspension facilitates red cell agglutination

28
Q

what is the indirect anti-globulin test?

A

reagent red cells expressing known antigen(s)
patient plasma is added
anti-human globulin is added
look for agglutination (indicates presence of an antibody)

29
Q

how is blood selected for transfusion?

A

matched for, or compatible with, patient’s ABO and RhD group
consider presence of RBC antibodies
perform crossmatch to check donor cells are compatible with patient plasma

30
Q

how is an IAT crossmatch performed?

A 
donor red cells in test tube
patient plasma is added
anti-human globulin is added
look for agglutination 
- agglutination = donor cells are incompatible with patient plasma
- no agglutination = compatible
31
Q

indications for RBC transfusion (rather than tablets)?

A

symptomatic anaemia with Hb <70g/L (80g/L if cardiac disease also present)
major bleeding
transfuse a single unit of RBCs and then reassess

32
Q

indications for platelet transfusion?

A

prophylaxis in patients with bone marrow failure and very low platelets
treatment of bleeding in thrombocytopenic patient
prophylaxis prior to surgery/procedure in thrombocytopenic patient

33
Q

indications for fresh frozen plasma (FFP) transfusion?

A

treatment of bleeding in patient with coagulopathy (PT ratio >1.5)
prophylaxis prior to surgery or procedure in patient with coagulopathy (PT ratio >1.5)
management of massive haemorrhage (trauma)
not in absence of bleeding/planned procedure

34
Q

how is a transfusion requested?

A 
multi-step process
correct labelling of sample
- name, ward, gender, DOB, date and time of sampling, CHI number, signature
document consent for transfusion
blood authorisation document
document transfusion and return to lab
35
Q

how is transfusion monitored?

A

observations before blood is commenced
observations at 15 mins
observations within 60 mins of completion

Haematology (26 decks)

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