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Blood and Drugs > B10 - Blood groups and blood transfusion > Flashcards

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
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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
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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
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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
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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.
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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
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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
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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
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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’
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10
Q

Blood Fractionation and Components

A 
- Major components 
		○ Packed red blood cells 
		○ Fresh frozen plasma 
		○ Platelets 
		○ Cryoprecipitate
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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
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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
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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
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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
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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

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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
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
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

Blood and Drugs (29 decks)

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