Blood Transfusion

Question 1

what makes a blood group a specific blood group?

Answer 1

presence or absence of antigens on surface of red cell membrane

Question 2

what defines type of antibodies on red cell membrane?

Answer 2

inherited from both parents

Question 3

blood grouping system?

Answer 3

ABO system

Question 4

types of blood group?

Answer 4

A (2nd most common)
B (3rd most common)
AB (least common)
O (most common)

Question 5

which antibodies are present in the plasma in people with each blood type?

Answer 5

A = anti-B antibodies
B = anti-A antibodies
AB = neither
O = anti-A and anti-B antibodies

Question 6

what happens if someone someone is given wrong blood type?

Answer 6

acute haemolytic transfusion reaction
i.e person with group A is given group B blood > group B blood contains anti-A antibodies which will attack A antigens on patients own RBCs causing lysis of the RBCs

Question 7

which blood groups can donate to each other?

Answer 7

O can donate to anyone (as they have no antigens on surface) but can only receive from group O as group O blood contains both anti-A and anti-B antibodies

group A can donate to A and AB (as they have only A antigens) but can only receive from group A or O (as group B has anti-A antibodies)

group B can donate to B and AB but can only receive from B and O

group AB can only donate to AB (as group A has anti-B, group B has anti-A and group O has both) and can receive from all groups (as AB blood contains no antibodies)

Question 8

another blood grouping system>

Answer 8

rhesus (RhD antigen)

Question 9

describe RhD antigen?

Answer 9

inherited antigen composed of 2 alleles (D and d - d is recessive)
very immunogenic (exposure to tiny bit of D antigen causes reaction forming anti-D antibodies)

Question 10

rhesus +ve vs -ve genotype?

Answer 10

\+ve = DD or Dd
-ve = dd

Question 11

why is formation of anti-D antobodies harmful?

Answer 11

can cause problems with blood transfusions in the future causing a transfusion reaction
anti-D antibodies can cross the placenta in pregnant women causing haemolytic disease of the newborn if rhesus -ve mum is carrying rhesus +ve baby

Question 12

other families of RBC antigens aside from ABO and RhD are usually less immunogenic, what does this mean?

Answer 12

less likely to form antibodies if exposed to something

but may still form antibodies when exposed to foreign RBC antigens

Question 13

when might someone be exposed to foreign RBC antigens?

Answer 13

pregnancy (exposed to foetal blood during haemorrhage etc)

transfusion

Question 14

antibodies formed in response to foreign antigen tend to be which type?

Answer 14

IgG rather than IgM meaning that the haemolytic transfusion reaction is more delayed

Question 15

what is blood tested for when a sample is sent before a blood transfusion?

Answer 15

ABO and RhD group
antibody screen
can be done via electronic crossmatch (if antibody screen in -ve) or wet crossmatch (where donor red cells mixed with sample of patient plasma if patient blood sample contains antibodies)

Question 16

risks of transfusion?

Answer 16

infection (bacterial, viral, prion etc)
acute reaction
fluid overload

Question 17

questions to ask self before giving transfusion?

Answer 17

cause of anaemia if giving for anaemia
think whether anaemia is symptomatic (usually not needed if asymptomatic)
any other medical problems?

Question 18

restrictive transfusion threshold?

Answer 18

NICE threshold for giving RBC transfusion which advises to only give it if Hb <70, aiming for Hb 70-90
deemed safe in people with normal bone marrow

Question 19

alternatives to transfusion?

Answer 19

replace iron/B12/folate
minimise blood loss (tranexamic acid (antifibrinolytic) for example)
intraoperative cell salvage plus reinfusion

Question 20

what is irradiated blood?

Answer 20

blood which has been exposed to irradiation which kills viable donor lymphocytes present in blood component to prevent transfusion associated graft vs host disease (GVHD)

Question 21

when does GVHD happen?

Answer 21

when the lymphocytes present in the blood which is transfused engraft into the patients bone marrow and start basically making an immune system which fights against the patients own tissues
usually only occurs in people who are immunosuppressed but is universally fatal

Question 22

who should receive irradiated blood?

Answer 22

immunosuppressed
people who have been treated with purine analogue chemotherapy
people who have undergone autologous or allogenic stem cell transplant (only require irradiated blood short term)

Question 23

what is CMV -ve blood?

Answer 23

blood which has been specifically irradicated of cmv (only a very small risk of CMV transmission in normal blood components)

Question 24

when is CMV -ve blood used?

Answer 24

for people who would be at risk of harm if they contracted CMV
e.g pregnant women (can cross placenta and cause foetal morbidity), neonates

Question 25

steps in taking a patient blood sample pre-transfusion?

Answer 25

confirm patient identity
take the sample
label the sample at the bedside (never wait until later incase you forget)

Question 26

how do you label a sample?

Answer 26

forename
surname
ward
gender
DOB
date and time of sample
CHI number
signature

Question 27

what is a second sample policy?

Answer 27

safety step used in many hospitals to prevent mistakes in transfusion
states that blood shouldnt be given until patient ABO group has been confirmed on 2 occassions (2 samples taken at separate events)

Question 28

how quickly must a red cell transfusion take place?

Answer 28

within 4 hrs of leaving the fridge

can be delivered within 2-3 hrs if patient can tolerate it

Question 29

checks before blood is collected from bloodbank?

Answer 29

ensure patient is correctly identified on wrist band
ensure patient has a working venflon (IV access) with patient safety bundle adhered to
ensure blood authorisation form has been completed correctly (check for special requirements etc)

Question 30

checks before blood is connected to the patient? (dont remove blood from packing until these checks are performed)

Answer 30

check blood bag label - date/time removed from storage
inspect bag condition, expiry date etc
record baseline observations in NEWS chart
verbal identification at bedside
verify identity with wristband match with details on blood bag
check traceability bag and tag” label
sign “bag and tag” label with starting date and time recorded

Question 31

which part of the transfusion tag has to be returned to the lab?

Answer 31

blue part

Question 32

how are transfusion patients monitored?

Answer 32

do NEWS observations before start of transfusion, 15 mins after starting (transfusion reactions usually happen early)
repeat again within 60 mins of completing transfusion
(do an extra set of obs if something changes to make you concerned i.e patient feels feverish or unwell etc)

Question 33

checks at end of transfusion?

Answer 33

record date and time of completion
completion of observations noted on NEWS chart
disconnect patient or repeat process if more units needed

Question 34

describe features of an acute transfusion reaction

Answer 34

usually happens early in transfusion
causes - chills, rigors, rash (can be an urticarial/allergic looking), flushing, feeling of impending doom, collapse, loin pain, resp distress, fever, tachycardia, hypotension, tachycardia