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Flashcards in Transfusions Deck (33)
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1
Q

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

A

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

2
Q

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

A

HIV, Hep C, Hep B, HTLV, syphilis

3
Q

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

A

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

4
Q

What is made available at the transfusion lab?

A

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

5
Q

Where is the gene for the ABO grouping system found?

A

Chromosome 9

6
Q

What do A and B genes code for?

A

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

7
Q

In the ABO system, which is dominant?

A

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

8
Q

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

A

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

9
Q

How is your ABO group inherited?

A

One ABO gene from each parent

10
Q

What is Landsteiner’s law?

A

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

11
Q

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

A

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

12
Q

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

A

RhD 85% of population are RhD positive

13
Q

How is RhD inherited?

A

2 alleles D and d, inherit one from each parent

14
Q

What can anti-D antibody cause?

A

Transfusion reactions and haemolytic disease of the foetus and newborn

15
Q

What should be avoided in RhD negative people?

A

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

16
Q

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

A

Not as immunogenic

17
Q

Why is pre-transfusion testing important?

A

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

18
Q

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

A

Antisera - a reagent with known antibody specificity

19
Q

What is used to identify antibodies present in the plasma?

A

Reagent red cells - red cells with known antigen specificity

20
Q

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

A

Agglutination of red cells

21
Q

How is a patient’s ABO blood group identified?

A

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

22
Q

What does an IAT crossmatch check for?

A

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

23
Q

What are some indications for red cell transfusion

A

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

24
Q

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

A

1 unit initially and reassess

25
Q

What are some indications for platelet transfusion?

A

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

26
Q

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

A

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

27
Q

When are patient’s obs done during transfusion?

A

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

28
Q

What are the signs and symptoms of acute transfusion reaction?

A

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

Signs - fever, tachycardia, hypotension

29
Q

What is the pathophysiology behind AHTR?

A

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
30
Q

How would the transfusion lab manage an AHTR?

A
  • 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
31
Q

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

A

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

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

32
Q

How is transfusion associated circulatory overload managed?

A

Oxygen, supportive care and diuretics

33
Q

What is a delayed haemolytic transfusion reaction?

A
  • 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