blood transfusion Flashcards
ABO system
chromosome 9
A+B genes code for transferases which modify precursors called H substance on red cell membrane
A+B are dominant (co-dominant) over O
O is silent
phenotype vs genotype
phenotype = which antigens are detected
genotype = which genes are present
example
phenotype = Group A
genotype = AA or AO
group AB = AB
Landsteiners law
when an individual lacks A or B antigen the corresponding antibody is prodcued in their plasma
naturally occurring antibiodies cause haemolysis of red cells expressing the specfic antigen
ABO group A, where/what antigens/antibodies are presented?
antigens present on RED CELLS = A
antibodies present in the PLASMA = anti-B
ABO group O, where/what antigens/antibodies are presented?
antigens present on RED CELLS = none
antibody present in the plasma = anti-A AND anti-b
ABO group B, where/what antigens/antibodies are presented?
antigens present on RED CELLS = B
antibody present in the plasma = anti-A
ABO group AB, where/what antigens/antibodies are presented?
antigens present on RED CELLS = A AND B
antibody present in the plasma = neither
reagent to detect antibody/antigen specificity in pre-transfusion testing
reagent with known antibody specificity to identify antigen present on red cell -> antisera
red cells with known antigen specificity to identify antibodies present in plasma - > reagent red cells
how are patients blood groups defined
- Test patient’s red cells with anti-A, anti-B and anti-D antisera
a. Identify antigens on the red cells
b. IgM reagents – direct agglutination - Test patient’s plasma against reagent red cells of group A and group B
a. Identify antibodies in the plasma
which reagents would show positive agglutination in blood group A positive?
patient RED CELLS + anti-A
pateint RED CELLS + anti-D
patient PLASMA + group B cells
which reagents would show positive agglutination in blood group O positive?
patient RED CELLS + anti-D
patient PLASMA + group A cells
patient PLASMA + group B cells
indirect antiglobulin test
reagent red cells expressing know antigens
- add patient plasma
- add anti-human globulin
look for agglutination
indirect coombs test
detect antibodies in SERUM
method
- add patients PLASMA to RBCs with known antigen
- add Coombs reagent
- compare similarities in positive samples
uses
- pre-transfusion-testing - blood types, crossmatching
- pre-natal antibody screen - IgG antibodies that can cross the placenta
*CANNOT detect complement (complement on surface)
indications for red cell transfusion
- SYMPTOMATIC anaemia - Hb <70 - <80 if cardiac disease
- major bleeding
always consider alternative
transfuse a single unit of red cells then reassess
dications for platelet trnsfusion
- prophylaxis in patients with bone marrow failure + very low platelet counts
- treatment of bleeding thrombocytopenic patient
- prophylaxis prior to surgery/procedure in thrombocytopenic patient
always consider cause before transfusion
indications for FFP (fresh frozen plasma)
- treatment of bleeding patients with coagulopathy PT >1.5
- prophylaxis prior to surgery or procedure in patient with coagulopathy PT >1.5
- management of massive haemorrhage
transfuse early in trauma
do NOT give in absence of bleeding/planned procedure
monitoring patient during transfusion
observations before blood is commenced
observations at 15 mins
observations within 60 mins of completion
examples of blood product transfusion complications
immunological - acute haemolytic, non-haemolyic febrile, allergic/anaphylaxis
infective
transfusion related acute lung injury (TRALI)
transfusion associated circulatory overload (TACO)
other - hyperkalaemia, iron overload, clotting
non-haemolytic febrile reaction
due to white cell HLA antibodies
often result of sensitisation by previous pregnancies or transfusions
features
- fever, chills
- red cell transfusion - 1-2%
- platelet transfusion 10-30%
management
- slow or stop transfusion
- paracetamol
- monitor
minor allergic reaction
caused by foreign plasma proteins
features = puritus, urticaria
Mx = temporarily stop transfusion, histamine,monitor
anaphylaxis to blood product transfusion
patients with IgA deficiency who have anti-IgA antibodies
features = HYPOTENSION, dyspnoea, wheezing, angioedema
Mx = stop transfusion, IM adrenaline, ABC support (oxygen, fluids)
acute haemolyic reaction to blood products transfusion
ABO incompatible blood (secondary to human error) causing massive intravascular haemolysis
- usually result of red blood cell destruction by IgM type antibodies
features = fever, abdo pain, hypotension, agitation
- symptoms begin minutes after transfusion started
management
- stop transfusion
- confirm diagnosis - check info, repeat coombs test/crossmatching
- supportive care
transfusion associated circulatory overload (TACO)
excessive rate of transfusio, pre-existing heart failure
- old frail, chronic anaemia
common
fluid over loaf resulting in pulmonary oedema
transfusion associated circulatory overload (TACO) presentation + management
pulmonary oedema
HYPERtension
management
- slow/stop transfusion
- consider IV loop diuretic (furesomide) + oxygen
transfusion related acute lung injury (TRALI)
non-cardiogenic pulmonary oedema thought to be secondary to increased vascular permeability caused by host neutrophils that become activated by substance in donated blood
rare
onset within 6hrs of transfusion
features = hypoxia, pulmonary infiltrates on CXR, fever, HYPOTENSION
key presentation difference between TACO + TRALI
circulatory overload (TACO) = hyPERtension
acute lung injury (TRALI) = hyPOtension
graft verus host disease
delayed response - occurs within 100days of tranplantation
usually effects skin, liver + GI
fx = painful maculopapular rash (on neck, palms+sole)
jaundice
watery/blood diarrhoea
N+V
LFTs demonstate cholestatic jaundice
Mx = immunosuppression, steroidse
what is the purpose of requesting irradiated blood products
depleted T lymphocyte numbers reduce the risk of transfusion graft vs host disease
