BLOOD TRANSFUSION Flashcards
describe the ABO antigen system…
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.
Describe how blood is collected?
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
how are blood products tested and processed to minimise immune reactions and infections ?
leukodepletion - removes White cells
antibody screening
viral antibody screening
how are packed red cells stored?
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
how does SAG - M solution help with survival of packed red cells?
adenine - increases ATP
glucose - increases energy for glycolysis
mannitol - osmotic stabiliser prevents haemolysis
what limits packed red cell survival?
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.
how is FFP stored?
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)
how many donors do blood products come from?
RBC - one donor
FFP = one donor
platelets = pooled from 4 to 5 donors
how are platelets stored?
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.
when are platelets contraindicated?
TTP - causes coagulopathy
who can give blood?
17 to 66yrs
healthy / not currently ill
>50kg
never
- used IV drugs
- had hepatitis
- men had sex with man
not at risk of HIV
what blood products do you know?
Packed red cells
Fresh frozen plasma
platelets
cryoprecipitate
Prothrombin complex concentrate
Human albumin solution
what is prothrombin complex concentrate?
also known as beriplex
contains factors 10, 9, 7,2
reverses warfarin/ liver disease
what is cryoprecipitate?
fibrinogen
Plus 8, 13, vWF
haemophilia, von willibrand disease, DIC
when prescribing blood in immunocompromised patients, what precautions should be taken?
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
can you explain this table…
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
what is group and save and cross match?
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
what is the rhesus blood system?
rhesus is an antigen present on RBC - D antigen present in 85% of UK population.
why might someone have anti D antibodies?
IgG antibodies are generated when a rhesus negative person is exposed to rhesus positive blood
e.g. mother and baby
what is the significance of rhesus D system in pregnancy?
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
Can you classify the different transfusion reactions…
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
what is TRALI
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
what is TACO?
transfusion associated circulatory overload
presents as HF due to excess fluid
slow/ stop transfusion + furosemide 40mg IV + O2
what is acute haemolytic anaemia?
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
how is a acute haemolytic anaemia blood transfusion delt with?
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
what is a non-haemolytic febrile transfusion reaction?
common and usually mild
due to recipient antbodies against donor leukocyte antigens
release of cytokines e.g. IL1 and TNF
causes fever
monitor + antipyretic
what is delayed transfusion reaction?
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
what blood borne infections can you get from transfusions? how is this minimised
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
what constitutes a massive blood transfusion?
the replacement of circulating blood volume within 24 hour
OR 10 units in 6 hrs
what are the problems with massive blood transfusion?
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
what blood products should be given in a massive haemorrhage?
1:1:1
platelets: RBC : FFP
why should you check calcium in haemorrhage?
calcium needed for effective clotting
blood transfusion can lower calcium
calcium gluconate / chloride given if low.
what other blood conserving strategies are there?
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
what is cell salvage? pros and cons
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.
what is meant by allogenic and autologous ?
allogenic = from someone else
autologous = from self
when can recombinant factor VIII be used?
haemophilia
