Blood Transfusion

Question 1

Haemolytic transfusion reaction

Answer 1

Where incompatible red cells are transfused eg the transfused rbc have the antigen which corresponds to the antibody in the patients plasma

Question 2

Haemolytic disease of the fetus and newborn

Answer 2

Fetus has a different rbc antigen to mother and mother produces antibody to that rbc antigen that crosses the placenta

Question 3

ABO antibodies

Answer 3

Anti A and anti B (ABO) are mostly IgM antibodies that remain the same throughout life and don’t class switch. Interactions between IgM and rbc antigen cause agglutination

Question 4

How do IgM ABO antibodies cause acute HTRs

Answer 4

Though activation of the complement system
Can’t cause HDFN as they don’t cross placenta

Question 5

Some IgG exist which can cross placenta but don’t cause HDFN why

Answer 5

Fetal cells have poorly developed ABO antigens which can’t support binding of IgG antibodies
Any maternal IgG anti a or b will disappear after birth and baby develops on IGM

Question 6

Acquired alloantibodies

Answer 6

Usually IgG antibodies
Formed as a result of active immunization to non self rbc antigens following exposure to rbcs from another individual

Question 7

How does exposure of rbcs from another individual arise

Answer 7

Incompatible blood transfusion where RhD + transfused to RhD -
Fetal rbc can enter maternal blood eg RhD - Mum and + fetus
Can cause HDFN as can cross placenta

Question 8

ABO system

Answer 8

Formed by adding in sugar residue onto common glycoproteins
Group O has neither A or B and has H antigen
A and B are codominant
I is recessive

• A gene codes for an enzyme that adds N-acetyl galactosamine to the common H antigen
• B gene codes for enzyme which adds galactose

Question 9

ABO antibodies and antigens

Answer 9

Group A: anti b antibodies,A antigens in blood
Group B:anti a anitbodies,B antigens in blood
AB:no antibodies,A and B antigens
Group o:anti a and anti b,no antigens

Question 10

Who can blood be given too

Answer 10

To prevent acute HTRs, ABO compatible red cells should be selected for transfusion i.e. Group A red cells for a Group A patient. However, in emergency situations, where the group of the patient is not yet know, the universal donor is given to patients

Question 11

Platelets should have the same ABO group as

Answer 11

Reduce the risk of a poor response to the platelet transfusion due to anti-A or anti-B antibodies in the patient’s plasma causing destruction of the transfused platelets. . Low chance as expression on platelets is low
Reduce risk of Haemolysis which occurs in high titre negative a or b

Question 12

Fresh frozen plasma or cryoprecipitate

Answer 12

FFP or cryoprecipitate of the same ABO group as the patient should be selected for transfusion where possible to reduce the risk of haemolysis of the patient’s red cells by anti-A or anti-B antibodies in the plasma. If FFP or cryoprecipitate of the same ABO group as the patient is not available, FFP and cryoprecipitate of other ABO groups can be transfused as long as they are ‘high-titre’ negative.

Question 13

Rh systemic

Answer 13

Most important antigen is D

RhD positive (if have D antigen) or RhD negative (if not)

• So RhD negative group comes from dd
• RhD positive group comes from DD or Dd
  D positive have no antibodies however negative can develop then if e posed to D positive cells

Question 14

2 implications of anti D antibodies

Answer 14

Future transfusion (if patient has been exposed to RhD +): must be given to RhD negative or anti D antibodies would react with RhD+ blood causing delayed HTR resulting in anemia etc
Haemolytic diseases of newborn: if RhD neg mother has anti-D antibodies formed from previous pregnancy then in next pregnancy if foetus is RhD positive, mother’s IgG anti-D antibodies can cross placenta (only IgG can do this) and attach to foetal RhD positive RBCs causing their haemolysis.
Can cause death or brain damage due to high billirubin levels

Question 15

How to avoid sensitization of RhD neg patients

Answer 15

RhD negative given RhD negative & RhD positive given RhD positive
RhD- can be given to +

Question 16

How do we prevent pregnant women who are RhD negative from forming anti-D antibodies?

Answer 16

If carrying RhD+ they’re given anti d immunoglobulin which destroys fetal + rhds before anti d bodies made
If she has already developed the antibodies she needs monitoring

Question 17

Which blood type is universal donor

Answer 17

O- very rare

Question 18

Universal acceptor

Answer 18

AB+

Question 19

Universal plasma donor

Answer 19

AB+ as plasma contains no antibodies

Question 20

Antibody screen

Answer 20

• This is performed to detect the presence of any acquired alloantibodies the patient may have developed.
• The patient’s serum is tested against panels of RBCs which together are known to express all of the clinically relevant RBC antigens.
  If screen negative then can be given

Question 21

2 step compatibility testing

Answer 21

Patient blood sample tests: ‘Group & Screen’

• 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 RBCs → shouldn’t react, if does (agglutinates) then is incompatible

Question 22

What are the 6 mandatory screening tests?

Answer 22

• HIV
• Hep B
• Hep C
• Hep E
• HTLV
• Syphilis

-
May do malaria,cmv or T cruzii test

Question 23

How is blood collected

Answer 23

1. Whole blood donation- Not efficient to use ‘whole blood’ (with RBCs, plasma, platelets all together) to transfuse patients as they normally only need 1 of these components
   
   • Blood is collected from a donor in its entirety and then separated (via centrifugation) into its component parts later in the laboratory. A single donation is approximately 470mls.
2. Apheresis- The donor is connected to an apheresis machine. Blood from the donor passes through the machine which separates out the particular component required (e.g. red cells, platelets, or plasma) and returns the remainder of the blood to the donor.

Question 24

1 unit

Answer 24

Whole blood or blood products derived from 1 single blood donation

-

Question 25

Packed red cells

Answer 25

Lasts 35 days
Stored at 4 degrees
Given to anaemic patients or blood loss patients

Question 26

Platelets given for

Answer 26

Platelet transfusions are required for the treatment of bleeding or to reduce the risk of bleeding in patients with low platelet counts (thrombocytopenia) or platelet dysfunction (e.g. due to certain drugs such as antiplatelet medication)

• There are 2 methods for producing platelets for transfusion:

1. Pooled platelets – this is where platelets separated from 4 whole blood donations are pooled together to make up 1 unit of platelets
2. Apheresis platelets – this is where a single donor donates 1 unit of platelets through apheresis
   Lasts 7 days at 22 devreees
   Eee constant agitation to ensure platelets are oxygenated

Question 27

FFP

Answer 27

bleeding in patients with clotting factor deficiencies- prolonged APTT and PT

(platelet count can be normal tho and so can fibrinogen conc)
3 years at 25 degrees

When it is required for transfusion, it must first be thawed in a waterbath. Once thawed, FFP must be stored at 4oC and used within 24 hours of thawing.

Question 28

Cryoprecipitate

Answer 28

contains fibrinogen, Factor VIII, von Willebrand factor and Factor XIII

Mainly used to treat bleeding or to reduce the risk of bleeding when the fibrinogen
level is low, which is usually as a result of major haemorrhage (dilutional coagulopathy) or disseminated intravascular coagulation (consumptive coagulopathy).

• Cryoprecipitate is made by slow thawing of FFP overnight until there is a precipitate. This precipitate is then re-suspended in a small volume of plasma and frozen to maintain the activity of the clotting factors.

Cryoprecipitate has a shelf-life of 3 years at -25oC. When it is required for transfusion, it must first be thawed in a waterbath. Once thawed, cryoprecipitate must be stored at room temperature and used within 4 hours of thawing.

Question 29

What is plasma-derived medicinal products given for, and how is it made?

Answer 29

Manufactured from the pooling of thousands of human plasma donations

The manufacturing process includes at least 2 viral inactivation steps such as heat treatment and the use of Solvent-detergent (SD).

Human albumin solution (HAS)

Clinical indications for HAS include:

• To replace plasma volume in patients with plasma volume loss e.g. due to burns or trauma
• To replace plasma in plasma exchange e.g in the treatment of autoimmune disorders
• To initiate diuresis in patient with low albumin e.g. due to liver or kidney disease

Immunoglobulin solutions

Clotting factor concentrates

Question 30

When can’t you donate blood

Answer 30

Recent infection
Tattoo
Use of antibiotics
Disease such as HIV,hepatitis b c e
Low bmi
Recent piercing

Question 31

Prothrombin complex concentrates

Answer 31

Contain factor II,VII,IX,X and can reverse effects of warfarin
Used far major haemorrage and bleeding