Transfusions

Question 1

What is the minimum criteria for men and women to donate blood?

Answer 1

Hb >135g/L in men Hb >125g/L in women Weight over 50kg

Question 2

Blood samples from patients for G&S undergo microbiological testing, what does this look for?

Answer 2

HIV, Hep C, Hep B, HTLV, syphilis

Question 3

How long are red cells, FFP and platelets stored respectively?

Answer 3

Red cells = 35 days at 4 degrees FFP = 3 years at -30 degrees Platelets = 7 days with agitation at 22 degrees

Question 4

What is made available at the transfusion lab?

Answer 4

Blood components - red cells, FFP, platelets, cryoprecipitate Blood products - anti-immunoglobulin, prothrombin complex concentrate Blood products from pharmacy - IV Ig, human albumin, specific Ig

Question 5

Where is the gene for the ABO grouping system found?

Answer 5

Chromosome 9

Question 6

What do A and B genes code for?

Answer 6

Transferases which modify a precursor called H substance on red cell membranes

Question 7

In the ABO system, which is dominant?

Answer 7

A and B are dominant over O A and B are co-dominant O is silent

Question 8

What are the potential genotypes for each group phenotype e.g. group O etc.

Answer 8

Group O - OO Group A - AA or AO Group B - BB or BO Group AB - AB

Question 9

How is your ABO group inherited?

Answer 9

One ABO gene from each parent

Question 10

What is Landsteiner’s law?

Answer 10

When an individual lacks the A or B antigen the corresponding antibody is produced in their plasma Naturally occurring antibodies cause haemolysis of red cells expressing the specific antigen

Question 11

According to Landsteiner’s law, which antigen and antibody will a person with ABO group A, B, AB and O have respectively?

Answer 11

A - antigen A, anti-B B - antigen B, anti-A AB - antigen A and B, no antibody O - no antigen, anti-A and anti-B

Question 12

What is the next most important antigen after A and B?

Answer 12

RhD 85% of population are RhD positive

Question 13

How is RhD inherited?

Answer 13

2 alleles D and d, inherit one from each parent

Question 14

What can anti-D antibody cause?

Answer 14

Transfusion reactions and haemolytic disease of the foetus and newborn

Question 15

What should be avoided in RhD negative people?

Answer 15

Exposure to D antigen through transfusion i.e. RhD negative blood to RhD negative people

Question 16

Why are other blood group systems (other than ABO and Rh systems) not as important?

Answer 16

Not as immunogenic

Question 17

Why is pre-transfusion testing important?

Answer 17

Allows identification of ABO and RhD group of patient and presence of clinically significant red cell antibodies i.e. allows selection of appropriate blood for transfusion

Question 18

What is used to identify antigens present on the red cell?

Answer 18

Antisera - a reagent with known antibody specificity

Question 19

What is used to identify antibodies present in the plasma?

Answer 19

Reagent red cells - red cells with known antigen specificity

Question 20

What happens when the antigen on red cells reacts with the antibody specific for antigen of interest?

Answer 20

Agglutination of red cells

Question 21

How is a patient’s ABO blood group identified?

Answer 21

Test patients red cells with anti-A, anti-B and anti-D antisera IgM reagents - direct agglutination i.e. if test is positive they have the antigen

Question 22

What does an IAT crossmatch check for?

Answer 22

Agglutination indicates donor cells are incompatible with patient plasma. No agglutination means cells can be issued for transfusion

Question 23

What are some indications for red cell transfusion

Answer 23

Symptomatic anaemia, Hb<70g/L or 80g/L if cardiac disease Major bleeding

Question 24

How many units of red cells are transfused at a time?

Answer 24

1 unit initially and reassess

Question 25

What are some indications for platelet transfusion?

Answer 25

Prophylaxis in patients with bone marrow failure and very low platelet counts. Treatment of bleeding in thrombocytopenic patient. Prophylaxis prior to surgery/procedure in thrombocytopenic patient

Question 26

What are some indications for fresh frozen plasma (FFP) transfusion?

Answer 26

Treatment of bleeding in patient with coagulopathy (PT ratio>1.5), prophylaxis prior to surgery or procedure in patient with coagulopathy, management of masssive haemorrhage, transfuse early in trauma

Question 27

When are patient’s obs done during transfusion?

Answer 27

Before blood is commenced, at 15 minute intervals and within 60 minutes of completion

Question 28

What are the signs and symptoms of acute transfusion reaction?

Answer 28

Symptoms - chills, rigors, rash, flushing, feeling of impending doom, collpase, loin pain, resp distress

Signs - fever, tachycardia, hypotension

Question 29

What is the pathophysiology behind AHTR?

Answer 29

Binding of IgM anti-A or anti-B antibodies to their corresponding antigen leads to complement activation and lysis of transfused cells

Release of inflammatory cytokines:

• Complement, kinin and coagulation systems all activated
• Shock, increased vascular permeability, disseminated intravascular coagulation, renal failure
• Often fatal

Question 30

How would the transfusion lab manage an AHTR?

Answer 30

• Repeat ABO and RhD group of pre and post transfusion samples - Is there a discrepancy?
• Direct antiglobulin test - is there antibody bound to donor cells?
• Repeat crossmatch - Are the donor unit(s) incompatible?
  
  • Send remains of unit for culture

Question 31

What are the clinical features and risk factors associated with transfusion associated circulatory overload?

Answer 31

Clinical features - respiratory distress, hypertension, raised JVP, positive fluid balance

Risk factors - elderly, cardiac failure, low albumin, renal impairment, fluid overload

Question 32

How is transfusion associated circulatory overload managed?

Answer 32

Oxygen, supportive care and diuretics

Question 33

What is a delayed haemolytic transfusion reaction?

Answer 33

• Patient mounts delayed immune response to red cell antigen- usually IgG
  
  • Positive DAT
• Extravascular haemolysis 5-10 days post transfusion
• Transfused cells destroyed
  
  • Hb may drop, raised bili, LDH
  • Positive DAT and detection of alloantibody