Blood Transfusion Flashcards
what is the extra sugar residue of A?
N-acetyl galactosamine
what is the extra sugar residue of B?
galactose
what is the extra sugar residue of group O?
no extra sugar, just fructose stem
what is inheritance pattern of A and B?
co-dominant genes
what is the inheritance of O?
recessive
which blood group is the universal donor?
O-
which blood group is the universal receiver?
AB+
which antibodies are present for a certain blood group?
the antibodies against antigens NOT present on the red cell in the person’s blood
which antibody type reacts to mismatched blood
what effect does this antibody have in incompatible transfusion?
IgM:
reactive at 37 degrees C causing a full complement cascade and haemolysis of red cells
can cause a fatal haemolysis
how is blood group determined as a test
a known anti-A and anti-B reagent is given
donor of same group is selected and cross-matched (check for agglutination)
how is the RhD gene inherited?
D is dominant
d is recessive
dd- no D antigen
DD/Dd- D antigen present
which two factors are used to name blood groups?
antigen present e.g. A, B, AB, O
RhD status (±)
when do RhD- make antibodies?
after exposure to RhD+ antigen
e.g. by transfusion or when pregnant with RhD+ child
which antibody type is made against the RhD antigen
IgG (not as potent as IgM)
what needs to be done if RhD+ blood (as its the more common blood type) to a RhD- person?
they have to to receive RhD- blood after the first transfusion otherwise the newly formed anti-D antibodies will react
[delayed haemolytic transfusion reaction]
what is HDN? what happens in HDN?
Haemolytic Disease of the New Born
- RhD- mother creates anti-D antibodies post-transfusion or in reaction to her RhD+ foetus in a prior pregnancy
- so if she is pregnant with a RhD+ child, the antibodies will cross the placenta to attack the unborn child’s RBCs
examples of other RBC antigens
RhC c, E, e
Kell
Duffy
Kidd
what is the issue created by the additional antigens present on RBCs
patient will create antibodies against these antigens, therefore need blood without the antigens present
they will need an antibody screen pre-transfusion
why are only components of blood given to patients?
- to avoid wasting blood
- certain components degenerate if stored as whole blood
- avoid fluid overloading
layering of blood sample after centrifugation
plasma top
platelets middle
RBC bottom
how are red cells stored
5 weeks at 4 degrees C
why are red cells usually not frozen?
they recover poorly after thawing
freezing is only done for rare groups
how is Fresh Frozen Plasma (FFP) stored
2 years at -30 degrees C
thawed 20-30 minutes before use
when would FFP be given
- bleeding with abnormal coagulation test results
- reversal of warfarin for urgent surgery
what does cyroprecipitiate contain?
therefore what uses does it have?
fibrinogen and F8
for massive bleeding and hypofibrinogenaemia
how are platelets stored
5 days at 22 degrees C
why is it necessary to know the blood group of the PLATELET donation?
platelets have a low level of ABO antigen so wrong ones are destroyed quickly
indication for the use of platelets
1) bone marrow failure (thrombocytopenia)
2) massive bleeding
3) surgery
4) cardiac bypass (patient is using anti-p drugs to prevent clotting)
Fractioned products examples
- F8 and F9: for use in haemophilia A and B, F8 for VWD
- Ig molecules for specific illnesses
- albumin for burns, plasma exchanges, severe liver and kidney conditions
what are the particular uses of certain fractionated Ig molecules?
- IM-Ig – Specific – tetanus, anti-D and rabies.
- IM-Ig – Normal globulin – broad mix in population (e.g. HAV).
- IV-Ig – Pre-op patients with ITP or AIHA (Autoimmune haemolytic anaemia).
how is blood transfusion kept safe
- testing for infections
- exclusion of donors by questionnaire (e.g. investigate risky behaviour)
what must donated blood be tested for?
o Hepatitis B and C. o HIV. o HTLV – Human T-Lymphotropic Virus. o Syphilis. o CMV or HEV.
what is the issue in detecting infections at a certain time point when looking for blood donors?
window periods of certain infections mean that the antibodies against the infection are too low to be detected in the system
people who are at high risk of contracting blood borne diseases are not accepted as donors as they may be in early stage of infection and have not yet developed antibodies in the window period
these antibodies can react
Prion disease example that can be transmitted by transfusion
vCJD
variant Creutzfeld-Jakob Disease
how are fractionated products made safer despite pooling from multiple donors?
Leucodepletion: white cells filtered out (prevent the uptake of vCJD prion into brain)
normally obtained from the USA:
what are the antigens and antibodies of O?
Can they received blood? if so, from who?
no antigens
antibodies for A and B
can not receive blood from anyone else but O
what are the antigens and antibodies of A?
A antigens
antibodies for B
can’t receive B but can receive O, A, AB
what are the antigens and antibodies of B?
B antigen
antibodies for A
can’t receive A but can receive O, A, AB
what are the antigens and antibodies of AB?
A and B antigens
no antibodies
can receive any blood (A,B,O)
can you give RhD- people RhD+ blood?
yes but…
if D- person receives D+ blood, they form anti-D antibodies, they should switch back to RhD- transfusions to avoid a delayed haemolytic transfusion reaction
nb in an emergency when the blood group of the patient is not known, O RhD- blood is given (will not have antigens, in case the patient does have anti-D antibodies)
RhD positive antigens and antibodies
D antigen
no antibodies
RhD negative antigens and antibodies
no antigen
antibodies formed after exposure to RhD+ blood in tranfusion or foetus
how is compatible blood identified?
grouping of the blood
antibody screening
how does hydrops foetalis (haemolytic disease of the new-born) arise during pregnancy?
- A woman who is RhD- may be exposed to RhD+ antigen from the foetus (as the father maybe be RhD+)
- if she produced anti-D antibodies, the IgG antibodies will cross the placenta in the next pregnancy and destroy the foetal red blood cells (if the foetus is RhD+)
how is the hydrops foetalis risk reduced?
RhD-ve girls and women of child bearing age are avoided sensitisation to RhD positive blood
how are red cells grouped using biochemical method?
the red cells are incubated with antibodies of known specificity
observe for agglutination indicating that the patient has the corresponding antigen
What is antibody screening?
recipient of transfusion has their PLASMA compared for compatibility to the donor’s red cells
this identifies any antibodies the patient may have that will react with the donor’s blood
“cross match”
remember that antibodies are found in the plasma
remember that serum excludes clotting factors
who are high risk groups in the donor exclusion criteria?
- infected with HIV, Hep B or C
- injected illegal or non-prescribed drugs including anabolic steroids
- given money or drugs for sex
- sex with any of the above; in HIV prevalent areas; men who have had unprotected oral/anal sex with another man or woman with such man
what are some other Rh blood groups determined in donations?
C, c, E, e and the K blood group
how is the risk of vCJD been reduced through transfusion in the UK?
- plasma from the UK is no longer used for fractionation
- all blood products are leucodepleted i.e. remove white blood cells
storage temperature and shelf life of red cells
2-6 degrees
35 day shelf life
storage temperature and shelf life of platelets
22 degrees (agitated) 5 days
storage temperature and shelf life of fresh frozen plasma
frozen
2 years
storage temperature and shelf life of cryoprecipitate
frozen
2 years
what are the uses of platelet transfusion?
- prophylaxis against thrombocytopenia
- thrombocytopenia
NOT for autoimmune thrombocytopenia as the antibodies will destroy the platelets
Fresh Frozen Plasma use
Once thawed (at 30-37ºC) – deterioration of clotting factors – use as soon as possible
what does cyroprecipitate contain?
factor VIII
fibrinogen
(therefore use for deficiencies )
what products can be made from blood fractionation?
- albumin
- factor VIII
- factor IX
- Ig (normal or specific)
