L20: Practical aspects of transfusion

Question 1

Pre-transfusion testing aims

Answer 1

• Provide red cells that will survive normally in recipients circulation
• To avoid haemolytic reactions

Question 2

Steps in ensuring safe transfusion

Answer 2

1. Correct patient identification, blood sampling and labelling at bedside
2. Determination of ABO and Rh(D) type of recipient
3. Antibody screen to detect significant antibodies
4. Selection of appropriate red cells for transfusion
5. Final cross match or compatibility test
6. Removal of selected red cell units from refrigerator
7. Final identity check at bedside

Question 3

3 main causes of death and major morbidity in transfusion

Answer 3

• Incorrect blood component transfused to patient
• Transfusion related lung injury
• Transfusion transmitted infection (mainly bacterial)

Question 4

Antibody screen

Answer 4

Anti-human Globulin technique

• Add human red cell to IgG antibody serum and incubate
• IgG coats red cells but does not agglutinate
• Washed 4 times to remove free IgG
• Add anti-human globulin and visual agglutination occurs (cross-linking of IgG)

Question 5

Group and screen

Answer 5

• Most samples coming to blood bank request this
• Used in surgical settings when likelihood of blood being required is low
• Antibody screen should be negative
• Serum keep in lab for 7 days (or up to 28)
• Red cells can be provided quickly when needed (in 15 mins)

Question 6

Compatibility testing

Answer 6

Three approaches

1. Full crossmatch - up to 45mins, when antibody screen is positive
2. Immediate spin crossmatch - 4-10mins, to detect ABO incompatibility
3. Computer crossmatching - <5mins, final ABO check

Question 7

Provision of red cells in emergencies

Answer 7

- Effective communication essential 
3 main approaches, often sequential:
1. Emergency O Rh(D) negative units 
2. Group specific blood
3. Provision of fully compatible blood

Question 8

Final bedside check

Answer 8

• Common source of error
• Should involve two people
• Check patient identity against compatibility label: full name, DOB, NHI, blood group

Question 9

Monitoring of transfusion

Answer 9

• Major problems likely to produce early signs/symptoms

- if problem: stop transfusion, maintain line with saline and seek advice

Question 10

Complications of transfusions - immunological

Answer 10

Early:

• Haemolytic reactions
• Febrile non-haemolytic reactions
• Transfusion related acute lung injury
• Reactions to proteins

Late:

• Delayed haemolytic reactions
• Post transfusion purpura
• Graft versus host disease

Question 11

Complications of transfusions - non-immunological

Answer 11

• Bacterial

- Viral transmission

Question 12

Acute transfusion reactions - differential diagnosis

Answer 12

(Difficult to differentiate on clinical grounds alone)

• Bacterial sepsis
• Immediate haemolytic transfusion reaction
• Anaphylaxis
• Circulatory overload
• Febrile non-haemolytic transfusion reactions

Question 13

Bacterial sepsis

Answer 13

• Rare but serious complication
• Contamination of blood component with bacteria able to produce an endotoxin
• Usually yersinia entercolitis
• Sudden onset of hypotensive shock within mins of starting transfusion
• Unrecognised will likely lead to serious morbidity or death
• Bacterial contamination of red cells rare because few bacteria able to grow at 4 degrees
• Contamination of platelet components more common as bacteria will grow at 22 degrees (platelets routinely cultured to reduce risk)

Question 14

Immediate haemolytic transfusion reaction

Answer 14

• Red cells transfused and immediately destroyed by ABs in recipient’s serum
• Rare but potentially very serious
• Usually caused by ABO incompatibility
• IgM binds to red cell antigen -> activates complement -> haemolysis -> DIC
• Main complications: renal failure or DIC
• Significant morbidity common, 10% fatal
• Usually preventable

Question 15

Signs and symptoms of immediate haemolytic transfusion reaction

Answer 15

Symptoms:
Fever, restlessness, retrosternal or loin pain

Signs: fever, hypotension, uncontrolled bleeding

Question 16

Extravascular haemolytic reaction

Answer 16

• IgG antibody in patient plasma directed against antigen on red cells (Rh, Kell etc)
• Complement activation does not occur/only early phase (to C3 only)
• Cells removed by macrophages in spleen
• Clinically indistinguishable from acute intravascular haemolysis

Question 17

Delayed haemolytic transfusion reaction

Answer 17

• Usually 7-10 days post transfusion
• Hb fall associated with mild jaundice
• Caused by anamnestic antibody response
• -> sensitisation by previous pregnancy or transfusion
• -> Antibody not detectable during pre-transfusion testing
• Antibody becomes easily detectable after 5 days
• Potentially avoidable

Question 18

Febrile non-haemolytic transfusion reactions (FNHTR)

Answer 18

• Common
• Most with platelet transfusion (also with red cell components)
• Fever >38C starts during transfusion, rigors
• Clinically indistinguishable from acute haemolytic reactions
• Uncomfortable but not serious
• Occur in response to cytokines and other biological response modifiers that accumulate in blood components during storage
• Frequency reduced with introduction of pre-storage leucodepletion

Question 19

Management of FNHTR

Answer 19

• Stop, main line with saline
• Investigate: samples to blood bank and blood cultures to exclude sepsis
• Give paracetamol, antihistamine (evidence poor), hydrocortisone (not recommended)

Question 20

Transfusion related acute lung injury (TRALI)

Answer 20

• Onset of lung injury within 6hrs of transf.
• On CXR see opacities throughout lung
• Donor plasma containing white cell ABs directed against host HLA ABs
• Agglutination of recipients neutrophils in pulmonary vasculature = stiff lung syndrome
• Major cause of morbidity and mortality in transfusion
• Reduce risk: use only male FFP, screen platelet pheresis donors for HLA antibodies

Question 21

Transfusion associated circulatory overload

Answer 21

• Patient’s underlying cardiovascular function major determinant of risk for volume overload
• Often difficult to distinguish from TRALI
• Stop transfusion and give diuretics
  At risk:
• Compromised cardiovascular function
• Volume overload state (renal failure, congestive heart failure)
• High transfusion volumes compared to patient’s intravascular volume e.g. elderly, small children

Question 22

Allergic reactions

Answer 22

Common and usually reactions to plasma proteins
Two types:
1. Anaphylaxis/anaphylactoid
- Rare
- Early onset severe reaction
- Hypotension, dypnoea, abdo cramps
- Usually IgG deficient with anti-IgA antibodies
2. Urticarial: common, itchy rash, slow transfusion and give anti-histamine