Blood Transfusions Flashcards
What do blood groups tell you?
The antigen that is present on the surface of erythrocytes
What class are the antibodies present in the plasma for blood groups?
IgM
At what temperature is IgM reactive?
37 degrees celsius
What are IgM antibodies capable of if incompatible blood is given or produced?
Potentially fatal haemolysis
How are A and B antigens on red cells formed?
Formed by adding one or the other sugar residue onto a common glycoprotein and fucose stem (H antigen) on the red cell membrane.
A gene
Codes for an enzyme that add N-acetyl galactosamine to the common H antigen
B gene
Codes for an enzyme that add galactose to the common H antigen
Which blood group is safe to give to anyone in an emergency, until the patient’s own group is known?
Group O blood because it has no ABO antigens.
O negative
What happens if red cells are incompatible with blood?
So if a patient is group B, they have anti-A antibodies present in their plasma. If you then add group A red cells - agglutination is seen (visual agglutination) which shows that these red cells are incompatible with the patients blood.
What is the most important antigen in the Rhesus system?
D antigen
What antibodies does RhD positive people make?
None
Frequency in UK population ( 85%)
When can people who are RhD negative make anti-D antibodies?
After they have been exposed to the RhD antigen - either by:
Transfusion of RhD positive blood
In women if they are pregnant with an RhD positive foetus
What class are anti-D antibodies?
IgG class antibodies
If an RhD negative patient has been given RhD positive blood what is the implication for any of their future transfusions?
Patient must be given RhD negative blood in the future otherwise their anti-D antibodies would react with the RhD positive blood causing the delayed haemolytic transfusion reaction with anaemia; high bilirubin (from breakdown of red blood cells); jaundice etc.
What is the pathophysiology of Haemolytic disease of the newborn?
Mother is RhD negative and has anti-D antibodies (sensitisation), then in her next pregnancy, if the foetus is RhD positive, the mother’s IgG anti-D antibodies can cross the placenta and attach to the RhD positive red cells of foetus and cause haemolysis of foetal red cells.
In severe cases of HDN what happens to the baby?
Hydrops fetalis and deaths
In less severe cases of HDN what happens to the baby?
Baby survives, but high bilirubin levels can cause brain damage or death
What class of antibodies can cross the placenta?
IgG
What blood type (red cells) is used as an emergency and why?
Group O negative as it lacks antigen A and B and also antigen D.
In order to provide ABO and RhD compatible blood for a patient needing blood transfusion, what do you need to test?
ABO and RhD blood groups on patient’s red cells.
An antibody screen on the patient’s plasma (group and screen)
Why is an antibody screen performed?
To exclude any clinically significant immune antibodies.
How is an antibody screen carried out?
Patient plasma is incubated with 2 or 3 different fully typed ‘screening’ red cells, which are known to possess all the blood group antigens which matter clinically.
What happens if the Ab screen is negative?
Any donor blood which is ABO & RhD compatible can be given
What happens if the Ab screen is positive?
The antibody must be identified with the use of a large panel of red cells. Donor units of blood that lack the corresponding blood group antigen are then chosen for cross matching with the recipient’s plasma prior to transfusion.
How do you determine a patients blood group?
Test patient’s red cells with known anti-A and anti-B antibody reagents (ABO)
Test patient’s red cells with known anti-D antibody and reagent (RhD group)
Who are donors in the UK and what age are they between?
Only volunteer, unpaid donor who are between 17-70 years of age.
When are donors excluded?
If they have any disease that might make blood donation hazardous for them e.g. cardiovascular/neurological disease, or if their blood would be hazardous for the recipient.
Why is donor education and self-exclusion of individuals who are at high risk of having contracted blood-borne infectious diseases essential?
Essential to ensure that individuals who are in an early infectious stage, in whom the infection is not yet detectable by any test (i.e. in the ‘window period’ of infection) do not donate.
What other RhD groups are determined in ‘group and screening’?
C, c, E, e and K blood group also determined (Done on most donations)
Tests for which diseases are performed on donated blood in the UK?
Hep B, C and R.
HTLV
HIV
Syphilis
Where have prion proteins been found?
Membranes of lymphocytes and platelets and the prions of variant Creutzfeldt-Jacob disease (vCJD) are found in lymphoreticular cells
What does accumulation of prion protein in the brain result in?
Neurological damage
What is it routine to treat patients only with?
Components which are required; platelets, red cells and factor VIII.
What does 1 unit of blood mean?
Whole blood or products derived from one single blood donation.
What is 1 unit of red cells packed in?
SAGM (saline, adenine, glucose and mannitol) nutrients (fluid plasma removed). SAGM nutrients used to for longer storage; shelf life 5 weeks.
What temperature are red cells stored at?
4 degrees celsius
(transfused through a ‘blood giving set’ - has filter to remove debris/clumps.
What is FFP?
300ml unit stored at -30 degrees celsius (frozen within 6hrs of donation to preserve coagulation factors); shelf-life 3 years. Thawing necessary (20-30 mins prior. proteins may denature due to excessive temperature).
When do you administer FFP?
Immediately to reduce coagulation factor degeneration at room temperature. Dose: 12-15ml/kg (3 units).
What is the purpose of FFP?
Used as replacement fluid in plasma exchange as well as supplying clotting factors.
What is cryoprecipitate prepared from?
plasma; contains fibrinogen, VWF, factor VIII and XIII and fibronectin - adequate fibrinogen concentration available for IV use. Derived from frozen plasma, thawed at 4-8 degrees celsius.
What is the shelf-life of cryoprecipitate?
3 years shelf-life at -30 degrees celsius.
What is the standard dose of cryoprecipitate?
Standard dose - 10 units (5x2)
When would you use cryoprecipitate?
Fibrinogen level low (inherited hypofibrinogenemia) and excessive bleeding.
What are pooled platelets?
Platelet from 4 donations pooled to constitute a single adult dose.
When would you use platelet concentrates?
Haematology patients with bone marrow failure (leukaemia); DIC; surgical requirement; cardiac bypass and patient on anti-platelet drugs.
What clotting factors are essential towards treatment of haemophilia A and B?
Factor VIII and IX
Recombinant factor VIII and IX alternatives are frequently used.
