W03_14 Principles of transfusion Flashcards
what’s special about group AB individuals?
they are universal RBC recipient, and universal serum donor
what’s special about group O individuals?
they are universal RBC donor, and universal serum recipient
what do anti-A or anti-B agglutinins do?
potent activators of the complement cascade that causes hemolysis
how do people normally get blood minor group antibodies?
some sort of foreign blood exposure, like needlestick, transfusion, pregnancy, etc.
what’s delayed hemolytic transfusion reaction?
hemolysis occurring 4-11 days after transfusion, due to minor group incompatibility
what’s hemolytic disease of the newborn?
when a fetus has incompatible minor group matching with the mother, who had the antibodies from a previous exposure (i.e. first pregnancy), and sends them across the placenta to destroy fetal RBCs
why do you see RBC agglutination in major group incompatibility?
the antibodies are usually IgM molecules
why don’t you see RBC agglutination in minor group incompatibility?
the antibodies are usually IgG molecules
what’s Coombs’ test?
antiglobulin test - adding antibodies to some blood. if there are existing antibodies attached, then they will agglutinate
what’s the direct antiglobulin test?
mix antibodies directly with erythrocytes; shows that erythrocytes had antibody bound to them already
what’s the indirect antiglobulin test?
mix plasma with erythrocytes, then add the antiglobulin; shows that plasma had anti-erythrocyte antibodies
what’s the most important minor group antigen?
RhD (rhesus factor D). this is the most common cause of hemolytic disease of the newborn
note: RhD- patients are give RhD- blood only.
also note: RdD- mothers with RhD+ fetuses are given Ig against RhD to protect the baby
when do we match minor group negative blood other than RhD?
only when the person already has an antibody to it, since the reaction is not often severe
what’s the difference between the blood cross-match testing versus and antibody screen?
the cross-match tests the actual unit of blood to be given
in an emergency with no ideas of the type of patient blood, what’s the safest type of blood to give?
O-neg
what molecule do we add to blood to prevent it from clotting?
citrate;
binds the calcium in the blood
what are some additives we put into blood donations to keep the RBCs alive?
glucose;
also: adenine and phosphate
how do we protect against contamination of donated blood units?
impossible for 100% sterility, so we try aseptic collection and storage, and keep refrigerated
how do we deal with the issue of short supply?
pay donors;
advertise and promote altruism
what’s the major issue with platelet donations?
they’re short-lived (short half life) and so are always in demand
what is the important component of plasma donations?
coagulation factors (VIII, V, fibrinogen)
how long can plasma be stored?
1 year @ < 18C
what do we get from fractionated plasma products?
albumin, factor VIII, IX, XI, immunoglobulin; can be kept for years via lyophilization
note: one vial of RhD antibody comes from 60,000 donors
okay
what’s apheresis?
collection of a single blood component from a single donor, replacing the rest into the donor body