BLOOD TRANSFUSION

Question 1

describe the ABO antigen system…

Answer 1

The ABO antigen system consists of oligosaccharides expressed on surface of many cells including RBC

H antigen = basic building block and then further modifications create A or B antigens. (O antigen = H with no modifications)

At the age of 6 months, antibodies develop and self antibodies are removed. Hence a baby with blood group A will have antibodies for the B antigen but not the A antigen. These are IgM antibodies

if this baby is exposed to antigen B its antibodies will bind to the surface and cause haemolysis of that RBC / tissue.

Question 2

Describe how blood is collected?

Answer 2

collected from donor into a citrate anticoagulation solution

separated into components for storage

separation creates
= buffy coat = white cells, platelets
= Red cells
= plasma

can be further separated to make FFP, packed red cells, platelets etc

Question 3

how are blood products tested and processed to minimise immune reactions and infections ?

Answer 3

leukodepletion - removes White cells

antibody screening

viral antibody screening

Question 4

how are packed red cells stored?

Answer 4

fridge (1-6 degrees)
1 unit per bag = 450ml
stored in various solutions to help shelf life

e.g. SAG - M = saline, adenine, glucose, mannitol = 5 to 6 week survival

Question 5

how does SAG - M solution help with survival of packed red cells?

Answer 5

adenine - increases ATP
glucose - increases energy for glycolysis
mannitol - osmotic stabiliser prevents haemolysis

Question 6

what limits packed red cell survival?

Answer 6

cells are metabolically active
when energy falls and intracellular ATP falls they will die.

also correlated with drop in 2,3 DPG

hence stored in cold to reduce cellular metabolism, given adenosine to help make ATP and glucose to prolong glycolysis.

Question 7

how is FFP stored?

Answer 7

1 unit = 200-300ml
stored frozen at -25 degrees
can be stored to 1yr
when needed, defrosted and used within 6 hrs

(takes 30 mins to defrost)

Question 8

how many donors do blood products come from?

Answer 8

RBC - one donor
FFP = one donor
platelets = pooled from 4 to 5 donors

Question 9

how are platelets stored?

Answer 9

150-300ml
stored at 22 degrees / room temp - deterioration of function in cold.
need to be on a shaking platform to prevent clotting.
lasts 3 days

higher risk of bacterial infections.

Question 10

when are platelets contraindicated?

Answer 10

TTP - causes coagulopathy

Question 11

who can give blood?

Answer 11

17 to 66yrs
healthy / not currently ill
>50kg

never
- used IV drugs
- had hepatitis
- men had sex with man

not at risk of HIV

Question 12

what blood products do you know?

Answer 12

Packed red cells
Fresh frozen plasma
platelets
cryoprecipitate
Prothrombin complex concentrate
Human albumin solution

Question 13

what is prothrombin complex concentrate?

Answer 13

also known as beriplex
contains factors 10, 9, 7,2
reverses warfarin/ liver disease

Question 14

what is cryoprecipitate?

Answer 14

fibrinogen
Plus 8, 13, vWF

haemophilia, von willibrand disease, DIC

Question 15

when prescribing blood in immunocompromised patients, what precautions should be taken?

Answer 15

all blood is leukodepleted - reduces risk of donor white cells and febrile transfusion reactions and CMV transmission

however to completely remove these immunosuppressed need…

irradiated blood - prevents T donor lymphocytes attacking recipient

CMV negative blood in those with stem cell transplant

Question 16

can you explain this table…

Answer 16

known Anti serum i.e. antibodies for A, B and none are added to different blood sample of unknown blood group.

the one without is acting as a control.

if the antigen is present in the same the antibody will bind and cause agglutination.

hence if antiB added to a sample causes agglutination then B antigen are present
if this also agglutinates with anti A then the blood group is AB

Question 17

what is group and save and cross match?

Answer 17

G+S = sample of blood taken and tested against known anti serum to determine blood group and antigen present

x match - mixing of donor and recipient blood checking for agglutination

Question 18

what is the rhesus blood system?

Answer 18

rhesus is an antigen present on RBC - D antigen present in 85% of UK population.

Question 19

why might someone have anti D antibodies?

Answer 19

IgG antibodies are generated when a rhesus negative person is exposed to rhesus positive blood
e.g. mother and baby

Question 20

what is the significance of rhesus D system in pregnancy?

Answer 20

rhesus negative mum plus rhesus positive baby - exchange of blood at child birth = mum produces antibodies against rhesus D

if next baby rhesus positive - IgG Ab can cross placenta and cause haemolytic disease of the new born.

anti D Immunoglobulins given to resus negative mum which will bind any fetal cells antigen D and prevent mum making antibodies to them

Question 21

Can you classify the different transfusion reactions…

Answer 21

Immediate
- acute haemolytic reactions
- TRALI
- TACO
- non haemolytic febrile transfusion reaction
- allergy / anaphylaxis
- electrolyte imbalances

early (days)
- delayed transfusion reactions

late
- infection - blood borne
- iron overload - damage to pancreas, heart, brain

Question 22

what is TRALI

Answer 22

transfusion related acute lung injury

occurs within 6 hours
presents like ARDS - infiltrates, low sats, fever, dry cough

due to donor Ab attacking recipient leukocyte antigen
causes lung inflammation and non cardiogenic pulmonary oedema

stop transfusion, O2 and support

Question 23

what is TACO?

Answer 23

transfusion associated circulatory overload

presents as HF due to excess fluid

slow/ stop transfusion + furosemide 40mg IV + O2

Question 24

what is acute haemolytic anaemia?

Answer 24

Occcurs due to Ab / antigen reactions between donor blood and recipient.
most severe one would be ABO incompatibility

Recipient Ab attack donor blood by binding antigen –> haemolysis through complement activation, cytokine release

presents as:
- fever
- dyspnoea, hypotension, flushing
- abdo pain, chest pain, flank pain
- DIC, renal failure
- jaundice

occurs within minutes

Question 25

how is a acute haemolytic anaemia blood transfusion delt with?

Answer 25

stop immediately
check identity and name on the unit
tell haematologist and send all back to haematology including giving set.
send FBC, UE, cultures to lab

give saline and O2

Question 26

what is a non-haemolytic febrile transfusion reaction?

Answer 26

common and usually mild

due to recipient antbodies against donor leukocyte antigens

release of cytokines e.g. IL1 and TNF

causes fever

monitor + antipyretic

Question 27

what is delayed transfusion reaction?

Answer 27

haemolytic reactions occuring >24hrs later
usually between 3-14 days
mismatch of minor blood group antigen e.g. rhesus, kidd

caused by IgG that develop from previous transfusions

Question 28

what blood borne infections can you get from transfusions? how is this minimised

Answer 28

hep B / C
HIV
CMV
HTLV - human T cell leukaemia virus
syphilis

all donors undergo questionnaire
all blood routinely tested for hep B antigen, HIV ab , Hep C RNA, HTLV Ab and sphylis ab

CMV negative blood is saved for immunocompromised people

Question 29

what constitutes a massive blood transfusion?

Answer 29

the replacement of circulating blood volume within 24 hour

OR 10 units in 6 hrs

Question 30

what are the problems with massive blood transfusion?

Answer 30

Disturbances to clotting:
- dilution of clotting factors, platelets
- lowers Ca
- hypothermia also reduces clotting

Changes to electrolyte balance
- hyperkalaemia
- hypoCa (citrate in blood product can bind Ca)
- acidosis - lactate in stored blood from anaerobic respiration

Hypothermia - arrhythmias, enzyme dysfunction, poor O2 delivery (O2 dissociation curve)

risk of ARDS - not understood why

Question 31

what blood products should be given in a massive haemorrhage?

Answer 31

1:1:1
platelets: RBC : FFP

Question 32

why should you check calcium in haemorrhage?

Answer 32

calcium needed for effective clotting

blood transfusion can lower calcium

calcium gluconate / chloride given if low.

Question 33

what other blood conserving strategies are there?

Answer 33

preventing blood loss:
hypotensive anaesthesia to minimise blood loss
anti-fibrinolytic agents - TXA

Preventing transfusion
accept lower Hb level e.g. above 70g/L in healthy individuals

preventing donor tranfusion:
Cell salvage
pre donation - patient can donate and use own blood.

other methods to improve oxygenation
- artificial O2 carriage products - none have been used in UK

Question 34

what is cell salvage? pros and cons

Answer 34

blood from bleeding patient is collected, processed and re-transfused

cost effective, less immune risks, accepted by jahovas witness

in obsteric haemorrhage mix of amniotic fluid could lead to amniotic fluid embolism, cancer risk of malignant cells. electrolyte disturbances and dilution of clotting factors.

Question 35

what is meant by allogenic and autologous ?

Answer 35

allogenic = from someone else
autologous = from self

Question 36

when can recombinant factor VIII be used?

Answer 36

haemophilia