Haem: Blood Tranfusions Pt.4

Question 1

Describe the storage and shelf-life of platelets.

Answer 1

Stored at 22 degrees for 7 days

NOTE: they are screened for bacteria before release

Question 2

What are clincial features of anaphylactic reaction to blood products.

Answer 2

Severe and life-threatening reaction that starts soon after start of transfusion

• Occurs within seconds/minutes
• Drop in BP
• Rise in HR
• Very breathless with a wheeze
• Laryngeal or facial oedema

NOTE: most allergic reactions to blood products are not this severe

Question 3

What is the mechanism of anaphylactic reaction to blood products?

Answer 3

Caused by IgE-mediated mast cell degranulation

Question 4

Which patient group is more likely to have severe allergic reactions to blood products?

Answer 4

IgA deficient patients - anti-IgA antibodies may develop in response to exposure to IgA in donor’s blood

Most likely to occur with plasma transfusion

Question 5

What are the signs of transfusion associated circulatory overload (TACO)? When does it present?

Answer 5

Signs are due to pulmonary oedema/fluid overload

• SoB
• Low oxygen saturations
• High HR
• High BP
• Raised JVP

Usually caused by a lack of attention to fluid balance (especially in cardiac failure, hypoalbuminaemia, extremes of age)

Presents within 6 hours of transfusion

NOTE: this is the most common pulmonary complication to transfuson

Question 6

What are the CXR features of TACO?

Answer 6

Fluid overload

Cardiac failure

Question 7

What are the main clinical features of TRALI?

Answer 7

Looks like ARDS

• SoB
• Drop in oxygen saturation
• Rise in HR
• Rise in BP

Question 8

What CXR features would you expect to see in TRALI?

Answer 8

Bilateral pulmonary infiltrates within 6 hours of transfusion, NOT due to circulatory overload and other causes.

Question 9

Outline the mechanism of TRALI.

Answer 9

• Anti-WBC antibodies (HLA or neutrophil) in donor blood interact with WBC in the patient
• Results in release of neutrophil proteolytic enzymes and toxic oxygen metabolites in the pulmonary vasculature
• This leads to lung damage

Mechanism actually not fully understood

Question 10

What are the main differences between TACO and TRALI?

Answer 10

JVP - raised in TACO, not in TRALI
Furosemide - response in TACO, not in TRALI

Question 11

How can TRALI be avoided?

Answer 11

Using male donors (haven’t been pregnant) who haven’t had a transplant or transfusion so they will not have produced antibodies against HLA

Question 12

What is alloimmunisation?

Answer 12

• The process of developing antibodies against an antigen
• 1-3% of people receiving transfusions will develop antibodies against an RBC antigen that they lack

Question 13

What are the consequences of alloimmunisation with regards to blood transfusions?

Answer 13

Delayed haemolytic transfusion reaction
- Repeat transfusion with blood containing the antigen will lead to extravascular haemolysis

• This is IgG mediated so will take 5-10 days

Question 14

What are the typical blood test results you expect to see during a haemolytic episode?

Answer 14

• High bilirubin
• Low haemoglobin
• High reticulocytes
• High LDH
• Positive DAT
• Haemoglobinuria (for a few days until haemolysis stops)

NOTE: U&E should be tested to check for renal failure. Also group and screen should be repeated to check for the development of new antibodies

Question 15

In which patient groups is CMV dangerous?

Answer 15

• Very immunosuppressed (e.g. SCT)
• Pregnant women
• Neonates

Usually removed by routine leukodepletion

Question 16

What is the dangerous effect of parvovirus infection?

Answer 16

Causes temporary red cell aplasia

Question 17

Which patients are most affected by parvovirus infection?

Answer 17

• Foetuses
• Patients with haemolytic anaemia (e.g. sickle cell disease)

Question 18

What precaution can be made by blood donation services to prevent transmission of vCJD?

Answer 18

Blood services exclude people who have had transfusions in the past as donors.

Question 19

Describe the mechanism of transfusion-associated GvHD

Answer 19

• Donor blood will contain some lymphocytes that are capable of dividing
• Normally, the patient’s immune system will recognise and destroy these foreign lymphocytes
• In the very immunosuppressed patients, the donor lymphocytes are not destroyed
• They begin to recognise patient HLA as foreign and begins attacking it
• This damages the gut, liver, skin and bone marrow

NOTE: this is always fatal

Question 20

What are the clinical manifestations of transfusion-associated Graft-versus-Host disease?

Answer 20

• Severe diarrhoea
• Liver failure
• Skin desquamation
• Bone marrow failure

Death then occurs within weeks to months