W03_14 Principles of transfusion

Question 1

what’s special about group AB individuals?

Answer 1

they are universal RBC recipient, and universal serum donor

Question 2

what’s special about group O individuals?

Answer 2

they are universal RBC donor, and universal serum recipient

Question 3

what do anti-A or anti-B agglutinins do?

Answer 3

potent activators of the complement cascade that causes hemolysis

Question 4

how do people normally get blood minor group antibodies?

Answer 4

some sort of foreign blood exposure, like needlestick, transfusion, pregnancy, etc.

Question 5

what’s delayed hemolytic transfusion reaction?

Answer 5

hemolysis occurring 4-11 days after transfusion, due to minor group incompatibility

Question 6

what’s hemolytic disease of the newborn?

Answer 6

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

Question 7

why do you see RBC agglutination in major group incompatibility?

Answer 7

the antibodies are usually IgM molecules

Question 8

why don’t you see RBC agglutination in minor group incompatibility?

Answer 8

the antibodies are usually IgG molecules

Question 9

what’s Coombs’ test?

Answer 9

antiglobulin test - adding antibodies to some blood. if there are existing antibodies attached, then they will agglutinate

Question 10

what’s the direct antiglobulin test?

Answer 10

mix antibodies directly with erythrocytes; shows that erythrocytes had antibody bound to them already

Question 11

what’s the indirect antiglobulin test?

Answer 11

mix plasma with erythrocytes, then add the antiglobulin; shows that plasma had anti-erythrocyte antibodies

Question 12

what’s the most important minor group antigen?

Answer 12

RhD (rhesus factor D). this is the most common cause of hemolytic disease of the newborn

Question 13

note: RhD- patients are give RhD- blood only.

Answer 13

also note: RdD- mothers with RhD+ fetuses are given Ig against RhD to protect the baby

Question 14

when do we match minor group negative blood other than RhD?

Answer 14

only when the person already has an antibody to it, since the reaction is not often severe

Question 15

what’s the difference between the blood cross-match testing versus and antibody screen?

Answer 15

the cross-match tests the actual unit of blood to be given

Question 16

in an emergency with no ideas of the type of patient blood, what’s the safest type of blood to give?

Answer 16

O-neg

Question 17

what molecule do we add to blood to prevent it from clotting?

Answer 17

citrate;

binds the calcium in the blood

Question 18

what are some additives we put into blood donations to keep the RBCs alive?

Answer 18

glucose;

also: adenine and phosphate

Question 19

how do we protect against contamination of donated blood units?

Answer 19

impossible for 100% sterility, so we try aseptic collection and storage, and keep refrigerated

Question 20

how do we deal with the issue of short supply?

Answer 20

pay donors;

advertise and promote altruism

Question 21

what’s the major issue with platelet donations?

Answer 21

they’re short-lived (short half life) and so are always in demand

Question 22

what is the important component of plasma donations?

Answer 22

coagulation factors (VIII, V, fibrinogen)

Question 23

how long can plasma be stored?

Answer 23

1 year @ < 18C

Question 24

what do we get from fractionated plasma products?

Answer 24

albumin, factor VIII, IX, XI, immunoglobulin; can be kept for years via lyophilization

Question 25

note: one vial of RhD antibody comes from 60,000 donors

Answer 25

okay

Question 26

what’s apheresis?

Answer 26

collection of a single blood component from a single donor, replacing the rest into the donor body