Blood Transfusions

Question 1

what is activating complement

Answer 1

are able to cause potentially fatal haemolysis (destruction of red cells) if incompatible blood is transfused.

Question 2

Blood group A (rbc type,antibodies in plasma and antigens in rbc)

Answer 2

rbc = a
antibodies in plasma= anti b
antigens in rbc= a antigen

Question 3

Blood group B

Answer 3

rbc type= b
antibodies in plasma= anti a
antigens in rbc= b antigen

Question 4

Blood group AB

Answer 4

rbc type= ab
antibodies in plasma= none
antigens in rbc= a and b antigens

Question 5

Blood Group O

Answer 5

rbc type= o
antibodies in plasma= anti a and anti b
antigens in rbc= none

Question 6

how are a and b antigens formed of red cells

Answer 6

by adding one or other sugar residue onto a common glycoprotein and fucose stem (H antigen) on the red cell membrane.

Group O has neither A or B sugars – H stem only

Question 7

What does the A gene do

Answer 7

Codes for an enzyme that adds N-acetyl galactosamine to the common H antigen

Question 8

What does the B gene do

Answer 8

Codes for the enzyme which adds galactose

Question 9

Are A and B genes co dominant

Answer 9

Yes

Question 10

Is O recessive or dominant

Answer 10

Recessive

Question 11

What are the possible genes for blood group A

Answer 11

AA or OA

Question 12

Possible genes for blood group B

Answer 12

BB or OB

Question 13

Why is it safe to give blood group O to anyone in an emergency

Answer 13

As group O has no ABO antigens

Question 14

RhD negative

Answer 14

dd

Question 15

RhD positive

Answer 15

DD or Dd ( is d gene codes for no antigen and is recessive)

Question 16

Can people who lack the RhD antigen make anti D antibodies

Answer 16

Yes, after they are exposed to the RhD antigen, either by transfusion of RhD positive blood or in women if they are pregnant with an RhD positive foetus. Anti-D antibodies are IgG class antibodies

Question 17

Implications of anti D antibodies on future transfusions

Answer 17

1) future transfusions; patient must in future have RhD negative blood (otherwise their anti-D would react with RhD positive blood - causesdelayed haemolytic transfusion reaction– with anaemia; high bilirubin (from breakdown of red cells); jaundice etc.).

Question 18

Implications of anti-D antibodies on HDN

Answer 18

haemolytic disease of the newborn-if RhD neg mother has anti-D, then in the next pregnancy, if fetus is RhD positive: mother’s IgG anti-D antibodies can cross the placenta (only IgG class antibodies can do this) – attach to the RhD positive red cells of the foetus and cause haemolysis of foetal red cells - if severe:hydrops fetalisand death. If less severe, the baby survives but after birth, the high bilirubin levels can cause brain damage or death.

Question 19

How to avoid sensitisation of RhD negative patients

Answer 19

• Transfuse blood of same RhD group

- Group O negative blood

Question 20

Steps needed to provide ABO and Rh compatible b

Pod

Answer 20

Test ABO and RhD blood groups of patients red cells and an antibody screen on the patients plasma ( group and screen),

Question 21

How is an antibody screen performed

Answer 21

• Patient plasma is incubated with 2 or 3 different fully typed’screening’ red cells, which are known to possess all the blood group antigens which matter clinically.
  * If the antibody screen is negative, any donor blood which is ABO & RhD compatible can be given.
  * If the antibody screen is positive, the antibody must be identified with the use of a large panel of red cells. Donor units of blood that lack the corresponding blood group antigen are then chosen for cross matching with the recipient’s plasma prior to transfusion.

Question 22

Compatibility testing before transfusing patients

Answer 22

. Patient blood sample (plasma + cells).
• ABO group (test patient’s red cells with known anti-A and anti-B reagents).
• RhD group (test patient’s red cells with known anti-D and reagent).
• Select donor blood of the same ABO & RhD group.
• Antibody screen +/- antibody panel, to identify antibody/ies.
2​.Cross-match:patient’s serum mixed with chosen donor red cells - should not react: if reacts (agglutinates) = incompatible.
Blood with X antigens will agglutinate with an anti-X reagent.

Question 23

Why may blood donors be excluded

Answer 23

if they have any disease that might make blood donation hazardous for them, e.g. cardiovascular/ neurological disease, or if their blood would be hazardous for the recipient (risk of viral, bacterial or parasitic infections, certain diseases or drugs).
Donor education and self-exclusion of individuals who are at high risk of having contracted blood-borne infectious diseases are essential to ensure that individuals who are in an early infectious stage, in whom the infection is not yet detectable by any test (i.e. in the’window period’of infection) do not donate.

Question 24

Infection testing done on all blood samples

Answer 24

HIV, hep B , hep C , hep E , HTLV and Syphillis

Question 25

Infection testing done on some samples

Answer 25

CMV, T.cruzil, Malaria. Blood test to exclude vCJD is not yet available

Question 26

How is blood separated

Answer 26

450 ml of blood is collected from donor into a sterile plastic bad containing an anti-coagulants and centrifuged. Not efficient to use whole blood as patients only need one component. Eg. When giving anemic patients red cell transfusion, they don’t need the excess fluid contained in the plasma part as this puts them at risk of fluid overload.

So whole blood is centrifuged into three parts:
Red cells bottom
Platelets middle
Plasma top
( then squeeze each layer into satellite bags and cut free)

Question 27

What could red cells given be used to treat

Answer 27

Anaemia without volume deficiency

Question 28

What could platelets given be used to treat

Answer 28

Platelet deficiency

Question 29

What could FFP given be used to treat

Answer 29

Any coagulation factor decline

Question 30

What could cyroprecipitate given be used to treat

Answer 30

Factor 8, VWF , 13 deficiency, fibrinogen , fibronectin ( made from FFP)