B10 - Blood groups and blood transfusion Flashcards
1
Q
ABO(H) Blood Group System
A
- Presence of A,B antigens on red cell surface
- Mendelian inheritance
- Products of A and B genes are enzymes
- A and B antigens present on RBC at birth
- Anti-A and Anti-B:
○ Present if lack A and B antigens respectively
2
Q
Anti-A and Anti-B antibodies
A
- IgM antibodies
- Naturally occurring: produced at 3-6 months
- Anti-A and B antibodies:
○ Clinically significant
○ Cause rapid intravascular haemolysis
○ Severe immediate transfusion reactions (intravascular)
Cause mild haemolytic disease of the newborn (us. Group O mother; group A baby
3
Q
Rhesus Blood Group System
A
- 40 antigens: C, c, D, E, e (NB: d does not exist)
- D gene present (RhD Pos) or absent (RhD Neg)
- Presence or absence of D determines Rh positive or Rh negative
- No naturally occurring anti-D antibody
- Anti-D only occurs in D neg after exposure to D Ag
- Rh(D) antigen is highly immunogenic:
○ Rh(D) negative person exposed to Rh(D) positive blood is likely to generate and anti-D antibody
○ Of importance in haemolytic disease of newborn
4
Q
Haemolytic Disease of the Newborn
A
- Allo-immune haemolytic anaemia
○ IgG antibodies from the maternal circulation to the fetus via the placenta
○ Fetal RBC destroyed by maternal antibodies (IgG Ab)
○ Usually Rh(D) negative mother & Rh(D) positive fetus
§ Anti-D made in 1st pregnancy
§ Subsequent pregnancy: maternal anti-D destroyed feta; Rh(D) positive RBC
5
Q
Other Major Blood Group Systems
A
- Kell (K/k) ○ Most people lack k antigen (90%) ○ K antigen is immunogenic ○ Anti-k can cause haemolysis - Duffy (Fy) ○ Malaria invades RBC through Duffy antigen - Kidd (Jk) ○ Antibodies can cause delayed haemolytic Tx reactions - Lewis (Le), P, Lutheran etc. etc.
6
Q
Recipient: indications for transfusion
A
- Transfuse due to clinical need
- Red cells may be used for
○ Treatment of clinically significant anaemia
○ Symptomatic deficit of oxygen carrying capacity
○ Unstable anaemia medical patients
○ Replacement of traumatic blood loss
○ Replacement of surgical blood loss
○ Anaemia secondary to bone marrow failure
- Red cells may be used for
7
Q
Pre-transfusion testing
A
- Blood group
○ To determine the ABO and Rh blood type- Antibody screen
○ To detect any unexpected antibodies in patient plasma that may cause a transfusion reaction (anti-c, k etc.) - Crossmatch (compatibility test)
○ To ensure donor red cells are compatible with recipient plasma (antibodies)
○ A lab test of donor red blood cells to be transfused and the patient’s plasma
○ A fail safe method of preventing incompatibilities between n=donor and recipient blood
- Antibody screen
8
Q
ABO and Rh(D) blood grouping
A
- Forward group: red cell grouping to detect A, B antigens on red cells
- Reverse group: plasma grouping to detect anti-A, B antibodies
9
Q
Blood components
A
- Packed red blood cells
- Platelets
- Fresh frozen plasma
- Cryoprecipitate
- Albumin
- Coagulation factor concentrates
- Immunoglobulins
- In WA we do not have ‘whole blood’
10
Q
Blood Fractionation and Components
A
- Major components ○ Packed red blood cells ○ Fresh frozen plasma ○ Platelets ○ Cryoprecipitate
11
Q
Packed red blood Cells
A
- Commonest blood component used ○ Haematocrit 60-70%, 250-300ml ○ Stored at 2-6 C for up to 42 days ○ Leucodepleted ○ Oxygen carrying capacity ○ Indications: (1 unit increases Hb by 10g/L) § Haemorrhage § Symptomatic anaemia § Anaemia and urgent surgery § Bone marrow dysfunction or failure
12
Q
Platelets
A
- Stored 20-24 C for up to five days
- Platelets in plasma (no red blood cells)
- Do not possess AB antigens
- ABO/ Rh compatible; no cross match required
- Indications
○ Thrombocytopaenia and bleeding or surgery
○ Prophylaxis (<20x10^9/L) - Effect: increased platelets count by 30-40 x 10^9/L
13
Q
Fresh frozen plasma
A
- Plasma only (contains antibodies)
- Contains all plasma proteins
- Stored at -30 C for up to 1 year
- Thawed before use
- Bag= 200ml; dose = 10-15ml/kg
- Indications: coagulopathic bleeding, massive haemorrhage/transfusion
- ABO compatible; testing is not necessary
- Group AB= universal donor
14
Q
Cryoprecipitate
A
- Plasma: prepared from FFP
- Contains anti-A, B antibodies
- Bag= 30-40ml
- Stored below -25 C
contains factor VIII, von willebrand factor, fibrinogen - Indications: fibrinogen deficiency, dysfibrinogenaemia
- ABO compatible; testing is not necessary
- Cryoprecipitate should be compatible with recipient red blood cells
15
Q
early transfusion reactions
A
○ Haemolytic transfusion reaction (ABO incompatibility)
○ Sepsis: bacterial contaminated blood product
○ Transfusion-related acute lung injury
○ Transfusion-associates circulatory overload (TACO)
○ Febrile non-haemolytic transfusion reaction
○ Urticarial (allergic) reactions
16
Q
intermediate transfusion reactions
A
(7-10 days)
○ Delayed haemolytic transfusion reaction
17
Q
late transfusion reactions
A
○ Viral infections, immune sensitisation, iron overload
18
Q
Acute Haemolytic Transfusion reaction
A
- A medical disaster: significant mortality
- Usually due to ABO incompatibility
○ E.g. group A blood into group O recipient
○ Acute haemolysis A cell binds circulating anti-A
○ Usually clerical, labelling or collection error - Avoided by paying careful attention to each step int eh transfusion process
○ Correct pre-transfusion sample
○ Laboritory quality systems
○ Bedside check prior to setting up the transfusion
- Usually due to ABO incompatibility
19
Q
Bacterial Contamination of blood products
A
- Risk 1:75 000
- Procedural changes intorduced in 2008
○ Blood products help 24 hours then tested
○ Bacteria during collection or preparation
§ Including water baths for FFP thaw
○ Fever, chills, circulatory collapse during or soon after transfusion - More common with platelets than with RBC
○ Due to being agitated
- Procedural changes intorduced in 2008
20
Q
Transfusion related acute lung injury
A
- Rare: 1:5000-1:100 000 (high mortality)
- Respiratory distress occurring <6 hr of transfusion
- Chest X-ray shows pulmonary oedema
- Donor antibodies reacting with patient neutrophils
21
Q
Transfusion related circulatory overload
A
- Up to 1% of transfusion
- Volume overload leads to cardiac failure
- Within 6 hours of transfusion
○ Acute respiratory distress
○ Tachycardia
○ Increased blood pressure
○ Acute or worsening pulmonary oedema
○ Evidence of positive fluid balance - Neonates and elderly at greatest risk
22
Q
Febrile and Allergic reactions
A
- Common 1% (severe anaphylaxis: 1:50 000)
- Recipient antibodies react with donor white cells or proteins
- Symptoms: pyrexia, urticaria, anaphylaxis
- Incidence of febrile reactions low due to use of leucodepleted red cell units
- Management is supportive
○ Antipyretics; antihistamines - Anaphylaxis:
○ Rare and a medical emergency
○ IgA deficient patients
23
Q
Hazards of massive transfusion
A
- Impaired oxygen transport ○ Poor RBC function - Haemostatic failure ○ Dillution and depletion of coagulation factors ○ DIC - Electrolyte and metabolic disturbances ○ Hyper- or delayed hypokalaemia ○ Citrate toxicity - Immunosuppression
24
Q
Patient blood management
A
- Transfusion is a temporary transplant
- Transfusion can kill
- Optimise bone marrow haemopoiesis
- Correct correctable causes of anaemia
- Transfuse only for clinical benefit
○ Untreatable symptomatic anaemia
○ Thrombocytopaenic bleeding
○ Coagulopathic bleeding - Use alternatives to blood if available
- Avoid transfusions if possible
25
Q
3 pillars of patient blood management
A
- optimise hematopoeisis
- minimise blood loss and bleeding
- harness and optimise physiological tolerance of anaemia
26
Q
NBA: PBM guidelines and strategy
A
- Patent blood management improves patient outcomes by improving the patient’s medical and surgical management in ways that boost and conserve the patient’s own blood. As a consequence of better management, patients usually require fewer transfusions of donated blood components thus avoiding transfusions-associated complications
