blood transfusion Flashcards
difference between ABO blood groups
everyone has a common STEM- group A has A sugar added onto stem, same for B, if O, no sugar added ie stem only, if AB, some stems have A, some have B
genes for ABO blood groups
A genes adds N-acetyl galactosamine, B adds galactose, O nothing (recessive)
effects of antibodies + frequency DIAGRAM
body produces antibodies to any antigen NOT present ie group O has anti A and anti B antibodies: 1) BAD- if person given wrong transfusion, antibodies are IgM, so activates complement cascade= lysis of RBC (fatal) (HAEMOLYTIC TRANSFUSION REACTION) 2) GOOD- in test tube, IgM antibodies react with antigen to cause agglutination= easy test for blood group in patient
testing blood groups
blood samples in test tube, tested with known anti-A and anti-B antibodies, if clumping for both, person AB
RH groups
RHD most important- if RhD positive (85% ppl), you have D antigen, if RhD negative, only have dd, no D antigen RhD negative can make anti-D antibodies AFTER exposure to RhD antigen- exposure means transfusion of RhD positive blood, or if you are a pregnant women and have a RhD positive fetus: UNLIKE ABO where antibodies produced from birth, MUST require initial exposure
anti-D antibodies
unlike ABO antibodies, they are IgG antibodies, so don’t activate FULL complement cascade system- still causes haemolysis (thus jaundice), but NOT fatal
implications of anti-D antibodies
future transfusions for patient needs RhD neg blood (as antibodies will react with RhD positive blood to cause HAEMOLYTIC TRANSFUSION REACTION= anaemia, jaundice etc) if RhD neg mother has 2 pregancies with RhD pos baby, mothers antibodies will attack foetus’s blood= potential death
other RBC antigens
before each transfusion, apart from testing ABO/RhD group, do an ANTIBODY SCREEN of plasma to test other antigens
blood components DIAGRAM
blood not just given to patient, its centrifuged into RBCs, plasma (coagulation factors) and platelets, so if person anaemia, only RBCs given rather than everything- less waste and better (excess fluid may overload patient) plasma may then be either FFP, cryoprecipitate (FFP which is thawed), or fractionated plasma (into all its different components)
RBC
1 unit from 1 donor, with shelf life of 5 weeks- rarely frozen
FFP
frozen withshelf life of 2 yrs- must be thawed. plasma contains ABO antibodies, so need to know blood group
requirements of FFP
bleeding+ abnormal coag test results to reverse warfarin effects
cryoprecipitate
contains fibrinogen and factor 8- needed for low fibrinogen
platelets
shelf life only 1 week– need to know blood group as well if patient A positive and B platelets given, platelets won’t last very long
requirements for platelets
most common those with bone marrow failure also bleeding and DIC
