M103 T2 L8 transfusion Flashcards
How do antibodies for ABO antigens occur?
naturally
due to cross reactivity with gut bacterial antigens
What are the functions of IgM antibodies?
able to fix complement and HEMOLYSIS
What are the four blood groups?
A - most common
O - second most common
B - rare
AB - very rare
What are the antigen and atby types for blood group A?
A antigens on rbc surfaces, B atbys in blood plasma
What are the antigen and atby types for blood group B?
B antigens on rbc surfaces, A atbys in blood plasma
What are the antigen and atby types for blood group AB?
both A and B antigens on rbc surfaces, no A or B atbys in blood plasm
What are the antigen and atby types for blood group O?
neither A or B antigens on rbc surfaces, both A and B antibodies in blood plasma
What are the antigen and atby types for blood group O?
neither A or B antigens on rbc surfaces, both A and B antibodies in blood plasma
What are the genotypes for the different blood groups?
OO
AA or AO
BB or BO
AB
How can gel cards be used for blood grouping?
blood from the sample is put in a tube and centrifuged
if the blood is at the top of the column, then there has been an agglutination reaction
if the blood is at the bottom, then there has been no reaction
the control should be negative
What is the function of gel cards?
for determining the blood type of a blood sample
Which blood group is protective for COVID19 and which is a risk factor?
protective - blood group O
rf - blood group A
How does the reverse grouping assay work?
by mixing the patients’ blood plasma with RBCs of a known type
What does the lab do when a sample is sent in?
they test the ABO group of the rbcs
they screen the plasma for atypical atbys
How do atypical antibodies arise?
sensitisation via foreign RBC antigens from blood transfusions or pregnancy
What can cause blood transfusion reactions?
Atypical antibodies if the patient is transfused with incompatible blood in the future
How does the Coombs test work?
uses anti-immunoglobulin antibody to agglutinate red cells
What are the two types of Coombs (anti-globulin) tests?
direct anti-globulin test (DAT)
indirect anti-globulin test (IAT)
What is the direct anti-globulin tests used for?
tells us if the rbcs are coated with antibody
In what circumstances does the direct anti-globulin test come back positive?
after a transfusion reaction and in HDN
in autoimmune haemolytic anaemia
What is a feature of people that are Rh positive?
can’t develop antibodies
What percentage of people are Rh negative?
15%
What are the exceptions for Rhesus sensitisation?
transfusion of Rh pos blood
pregnant with a Rh pos baby
What type of antibodies are developed by Rh negative people with rhesus sensitisation?
IgG-type antibodies
What is the most important antigen?
RhD
What are the potential effects of haemolytic disease of the newborn for the baby? (JAKern)
jaundice
anaemia
kernicterus
How does the direct anti-globulin test (DAT) work?
detects atbys stuck to the surface of the rbcs
since these atbys sometimes destroy rbcs, this test can help clarify anemia
How does the indirect anti-globulin test (IAT) work?
patient serum / plasma is incubated with rbcs
antihuman globulin is added
if an atbyis present in the serum, will cause agglutination between the rbcs and their corresponding antigens
What is the indirect anti-globulin test used for?
in the lab for testing blood group antigen
it detects antibodies floating freely in the blood
can tell us if a patient is positive for Rhesus and other blood groups b
What is a consequence of Rhesus D sensitisation?
Persons who develop Rh antibodies cannot be given Rh pos blood
What steps are taken to prevent haemolytic disease of the newborn?
Pregnant women have the ABO + Rh blood group check at 12 weeks
Rh-ve women (15%) receive anti-D antibody i.m. injection at 28 and 34 weeks to prevent sensitisation
Baby tested at birth and if Rh+ve, mother receives further anti-D until Kleihauer test (foetal cells) becomes negative
What steps are taken if a pregnant woman has already developed Rhesus sensitisation?
the foetus requires monitoring via trans-cranial Doppler scan
may require intra-uterine transfusions if signs of anaemia
What are the main componenets in a bag of donated blood?
Red cells Buffy coat Plasma Water Electrolytes Additives
What can low albumin levels indicate?
a problem with the liver or kidneys
What is the function of albumin?
to keep fluid in the bloodstream so that it doesn’t leak into other tissues
What is the purpose of apheresis?
to remove one particular component from blood
How does apheresis work?
remove whole blood from a donor or patient
separate the blood into individual components
re-introduced the remaining blood components back into the bloodstream of the patient / donor
What temperature are platelets stored at and for how long do they last?
stored at 22oC for 5 days
What temperature are rbcs stored at and for how long do they last?
stored at 4 oC for 35 days
What temperature is plasma stored at and for how long do they last?
stored at -30 oC for 12 months
What does a junior doctor need to know about blood transfusion?
When to give a blood transfusion What type of transfusion to give How to request blood transfusion How to monitor a blood transfusion What are the problems and complications
What circumstances should be met to give a blood transfusion?
Severe acute blood loss
Elective surgery associated with significant blood loss
Medical transfusions
Anaemia
Which three things constitute to Severe acute blood loss?
Severe trauma e.g., road traffic accident
Massive GI blood loss
Obstetric blood loss
What are examples of medical transfusions that might require a blood transfusion?
Cancer
chemotherapy
renal failure
What circumstances should be met to give a blood transfusion for anaemia?
only for symptomatic anaemia or if refractory to haematinic replacement
bone marrow failure
haemoglobinopathy
What are the components of donated blood?
Red cells
Platelets
Fresh frozen plasma
Cryoprecipitate (fibrinogen)
What are the plasma derivatives of donated blood?
Immunoglobulin
Coagulation factors
Albumin
What things must be in place before you can go ahead with transfusion testing?
Informed consent
Record reason for transfusion in notes
Sampler – ask patient their name and check ID on wristband
Make sure the patient gets the “Right blood at the Right time”
Most errors are caused by failure to follow procedures
What information must you obtain before you can go ahead with transfusion testing?
ID (surname, name, DOB, hospital number) Blood group Previous transfusions Reason for request Type of blood product and amount Special requests When and where Doctor (audit trail)
What information must be put on the blood sample label after performing a blood transfusion test?
ID
Signature of phlebotomist (audit trail)
Date
What information must NOT be put on the blood sample label after performing a blood transfusion test?
do not use addressograph labels
do not pre-label a sample
When testing for compatability between a sample blood test and a donor’s sample, what must be established?
the ABO and Rh groups
if there are atypical antibodies in patient serum
that the appropriate donor blood is chosen
that compatibility testing between donor cells and patient serum determines suitability
that the blood issued has the appropriate label
How long does it take to obtain O negative blood and when is it used?
5 mins
used in emergencies - referred to as emergency blood
is universal with all patients
How long does it take to obtain Group Compatible blood?
10 - 15 minutes
How long does it take to obtain “Fully screened and cross-matched” blood?
approximately 45 minutes
may be hours if antibodies are found
What are the potential reactions to blood transfusions?
Major ABO incompatibilities Febrile non-haemolytic reactions Fluid overload Anaphylaxis and severe allergic reactions Minor allergic reactions Delayed transfusion reactions TRALI
Which three things can major ABO incompatibilities lead to?
Acute renal failure
Disseminated intravascular coagulation
Death
What types of infections can be transmitted through blood transfusions?
Bacterial infections
Viral infections
Malaria
vCJD
What are three examples of bacterial infections that can be transmitted through blood transfusions?
syphilis
pyogenic infections
contamination infections (pseudomonas)
What are examples of viral infections that can be transmitted through blood transfusions?
hepatitis B, C HIV HTLV CMV West Nile virus
What are the potential physiological hazards to blood transfusions?
fluid overload
haemosiderosis
How can fluid overload be avoided?
do not infuse too quickly
transfuse 1 unit over 4 hrs if elderly or evidence of heart failure
What can fluid overload cause?
acute pulmonary oedema
How can fluid overload be treated?
with diuretics (frusemide) to remove fluid can transfuse 1 unit over 2 hours in younger patients
How does haemosiderosis occur?
iron is deposited in tissues
How is iron deposited in haemosiderosis?
liver
heart
pancreas
skin
How is haemosiderosis treated?
can treat by iron chelation
What is unique about IgM?
it is the largest ATBY
it’s the first ATBY to appear in the response to initial exposure to an antigen.
What is the shape of IgM?
pentameric
What is the Coombs test otherwise known as?
the anti-globulin test
What is the function of the Coombs test?
to detect ATBYs / complement proteins attached to the surface of rbcs
Which is more common Rh negative or positive?
positive
What does being Rh negative?
is not an illness and usually does not affect health
However, it can affect pregnancy
What do Rh antigens seem to be used for?
the transport of CO2 and/or ammonia across the plasma membrane
Where are Rh antigens located?
on the surface of RBCs
What is the gene that encodes Rh antigens?
the RHD gene
What is another term for Rhesus haemolytic disease?
Hemolytic disease of the newborn
When does Rhesus D sensitisation occur?
when a woman with RhD negative blood is exposed to RhD positive blood and develops an immune response to it
Which virus is associated with AIDS?
HTLV
What are the effects of vCJD?
psychiatric problems, behavioral changes and painful sensations
What is the function of forward grouping assays?
to test for which antigens are expressed on RBCs
What are the four main types of globulins?
alpha 1, alpha 2, beta, and gamma
What is the role of gobulins?
maintaining liver function, blood clotting, and fighting infection
What are the most significant gamma globulins?
antibodies
What is another term for ATBY’s?
immunoglobins
What substances are contained in the Buffy coat?
WBCs and Rh antigens
What is the most common reason for blood transfusion fatalities?
TRALI
