Blood transfusion

Question 1

How are antibodies stimulated in blood transfusion or pregnancy different to naturally occurring ones?

Answer 1

Antibodies stimulated by blood trans­fusion or pregnancy, such as Rh antibodies, are termed immune antibodies and are usually IgG

In contrast to naturally occurring antibodies, such as ABO antibodies, which are made in response to environmental antigens present in food and bacteria, and which are usually IgM

Question 2

Explain the ABO system:

Answer 2

Involved naturally occuring IgM anti-A and anti-B antibodies -> can cause rapid haemolysis or incompatible red cells

The A and B genes control specific enzymes that can add H. O gene is amorphic and does not transform H and is therefore not antigenic.

Question 3

Explain the Rh system:

Answer 3

IgG RhD antibodies are produced in RhD- after exposure to RhD+ red cells

Question 4

What tests are done pre-transfusion for compatibility?

Answer 4

Blood grouping - ABO and RhD

Antibody screening - plasma/serum screened against 2 group O donors for detecting IgM alloantibodies and IgG antibodies

Question 5

What is meant by group and save?

Answer 5

Where antibody screen is negative, blood is not reserved in advanced and can be made available quickly if needed in a few minutes using the electronic crossmatch procedure

Question 6

What is the most serious blood transfusion complication due to

Answer 6

ABO incompatibility

IgM antibodies lead to rigor, lumbar pain, dyspnoea, hypotension, haemoglobinuria and renal failure

Question 7

What is part of blood components?

Answer 7

Red cell
Platelets
Fresh frozen plasma - haemorrhage, DIC
Cryoprecipitate (Factor IIIC, von Willebrand factor and fibrinogen) - useful in DIC

Question 8

Fresh frozen plasma

Answer 8

Contains clotting factors, albumin and immunoglobulin.

Suited for clinically significant but not major haemorrhages in patients with a prothrombin time ratio or APTT of >1.5

Typically 150-220ml

Can be used prophylactically in invasive surgery where there is risk of significant bleeding

The universal donor of FFP is AB blood because it lacks any Anti-A or B antibodies

Question 9

Cryoprecipitate

Answer 9

Contains Factor VIII, XIII, von Willebrand factor, fibrinogen, and fibronectin.

Produced by further processing FFP, clinically it is used to replace fibrinogen.

15-20ml (smaller volume than FFP)

Suited for patients for ‘clinically significant’ but without ‘major haemorrhage’ who have a fibrinogen concentration < 1.5 g/L
For e.g. in DIC, liver failure, hypofibronigenemia, haemophilliacs, vW disease

Question 10

Prothrombin time complex

Answer 10

Used for emergency reversal of anticoagulation with severe bleeding
can be used prophylactically in patients undergoing emergency surgery depending on the particular circumstance

Question 11

What are cell saver devices?

Who may these be particularly acceptable in?

Contraindications?

Answer 11

These collect patients own blood lost during surgery and then re-infuse it. Types:
- Those which wash the blood cells prior to re-infusion. These are more expensive to purchase and more complicated to operate. However, they reduce the risk of re-infusing contaminated blood back into the patient.
- Those which do not wash the blood prior to re-infusion.
It may be acceptable to Jehovah’s witnesses.
C/I: malignant disease

Question 12

If urgent surgery is needed in patients taking warfarin, what should be done?

Answer 12

1. Stop warfarin
2. Vitamin K (reversal within 4-24 hours)
   IV takes 4-6h to work (at least 5mg)
   Oral can take 24 hours to be clinically effective
3. Fresh frozen plasma
   Used less commonly now as 1st line warfarin reversal
   30ml/kg-1
   Need to give at least 1L fluid in 70kg person (therefore not appropriate in fluid overload)
   Need blood group
   Only use if human prothrombin complex is not available
4. Human Prothrombin Complex (reversal within 1 hour)
   Bereplex 50 u/kg
   Rapid action but factor 6 short half life, therefore give with vitamin K

Question 13

What is now done to avoid transfusion-associated graft vs host disease?

What does CMV negative blood product mean?

Answer 13

Irradiated blood products are depleted of T-lymphocytes.

(CMV) is transmitted in leucocytes. As most blood products (except granulocyte transfusions) are now leucocyte depleted CMV negative products are rarely required.

Question 14

In a non-urgent scenario, a unit of RBC is tranfsused over what time?

Answer 14

90-120 mins

Question 15

What is the transfusion threshols and targent for RBC?

Answer 15

Treshold:

• without ACS: 70g/L
• with ACS: 80

Target after transfusion:

• 70-90 without ACS
• 80-100 with ACS