Blood Transfusion Flashcards
Why is blood trasnfused?
Insufficient blood - bleeding, failure of production and excess rate of destruction
Describe blood donors
Age, size, medications, infectious agents (sexual history, tattoos, prions), screen bloods for infectious agents (Hep B/ C/ E, HIV, syphilis) and blood tested for ABO and Rh blood groups
How are red blood cells prescribed?
By unit - 450ml from donor with red cell concentrate 300-400mls
Transfuse over 2-4hrs
1 unit increments - 5g/l
Stored at 4 degrees
What are the indications for red cell transfusion?
Correct severe anaemia which might cause organ damage
Improve QoL if un-correctable anaemia
Prepare patient for surgery or speed up recovery
Reverse damage caused by patients own cells - sickle cell anaemia
How are platelets given and stored?
1 dose platelets
Stored at -22 degrees and shelf life of 7 days
Transfuse over 20-30 minutes
When are platelets given?
Bone marrow failure, massive haemorrhage, prophylaxis for surgery, cardiopulmonary bypass and congenital platelet disorder
Describe fresh frozen plasma
Stored frozen and allow 30 mins to thaw
Indications are massive haemorrhage, DIC with bleeding, TTP and prophylaxis for procedures + deranged coagulation
Describe cryoprecipitate - plasma
1-2 pools if bleeding and fibrinogen under 1g/dl
Stored frozen and allow 20 mins to thaw
Fibrinogen concentrate now licensed
Describe blood groups
Arise from antigens - provokes an immune response - antibodies
Red cell antigens are expressed on cell surface
Type A has A antigens…
Type O then no antigens
Describe ABO blood group antigens
ABO gene encodes glycosyltransferase
Glycans added to proteins or lipids on red cells
A and B gene code for transferase enzymes
A antigen is N-acetyl galactosamine and B is galactose
O gene is a non-functional allele
Describe blood groups and their antibodies
A - have antibodies against B
B - have antibodies against A
O - antibodies against both
AB - no antibodies against A or B
IgM antibodies
What is the universal donor?
Blood group O
Which groups can blood group AB receive from?
All - A, B, AB and O
Describe Anti-RhD
RhD negative individuals can make anti-D if exposed to RhD positive cells in transfusion or pregnancy
Anti-D can cause transfusion reactions or haemolytic disease of new born
What is looked for in the group and screening?
ABO and RhD type
Checked against historical records
Screen of allo-antibodies in serum
How are allo-antibodies screened for?
Gel columns and automation
Grading of reactions
What is a coombs test?
Anti-human immunoglobulin which binds to FC portion of antigen antibodies
Red cells stick together
Used in cross-matching
Autoimmune haemolytic anaemia, passive anti-D and haemolytic transfusion reactions
Describe cross-matching
If antibody screen is negative and patient not at high risk of antibodies, can use electronic cross matching
High risk of antibodies - needs full cross match (patient plasma mixed with donor red cells)
When are non-cross matched blood given?
O negative in emergencies
Group specific blood to save our O negative stock
Low titre A+ FFP is safe for all groups
What blood group is most common for haemolytic disease of the newborn (HDN)?
RhD is most immunogenic
Other is c and K
How is HDN prevented?
Using prophylactic anti-D - sensitising events and routine at 28/40
What is the treatment for HDN?
Careful monitoring - antibody titres, doppler US and intrauterine transfusions
What are some cellular therapies?
Leucapheresis - stem cells
Lymphocytes
Other - bone, milk, tendons, heart valves, faecal, islet cells and mesenchymal stem cells
What are the risks of blood tranfusions?
Transfusion of ABO incompatible components
ATR (allergic) , TACO and TRALI
