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CVR > Blood Groups And Blood Transfusions > Flashcards

Blood Groups And Blood Transfusions Flashcards

1
Q

ABO typing

A

ABO system so potently antigenic because the antibodies occur naturally
• ABO antigens inherited in mendelian pattern
• Gene on chromosome 9 codes for an enzyme rather than the sugar itself
• Another gene codes for the sugar base of the ABO antigen
• A: dominant- 40%, has anti-B antibodies
• B: dominant- 12%, has anti-A antibodies
• AB: universal acceptor- 3%, no antibodies
• O: universal donor, 45%, no antigens but has both anti-A and anti-B antibodies
• Immunoglobulin M (IgM) antibody is mainly produced by the spleen- cannot cross placenta

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2
Q

ABO antigens

A

Made from carbohydrates not proteins
H antigen- different sugars on end create different A, B, AB, O antigens

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3
Q

ABO antibodies

A

Theorised they develop against environmental antigens
• Infants <3 months produce few if any antibodies (maternal prior to this)
• First true ABO antibodies > 3 months
• Maximal titre 5-10 years
• Titre decreases with age
• Mix of IgG and IgM
• IgM mainly for group A and B
• Wide thermal range means they are reactive at 37°C

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4
Q

Blood group A antibodies and antigens

A

A antigen
Anti-B antibodies

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5
Q

Blood group B antibodies and antigens

A

B antigen
Anti-A antibodies

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6
Q

Blood group AB antibodies and antigens

A

A and B antigens
No antibodies

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7
Q

Blood group O antibodies and antigens

A

No antigens (H antigens)
Anti_A and anti-B anti bodies

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8
Q

Which chromosome codes for ABO blood typing

A

Chromosome 9

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9
Q

Rhesus antigens

A

> 45 different Rh antigens
• Series of C, D and E antigens (D is the most important)
• D is a null gene so no protein so anti-D is not possible
• D is dominant- 15% of population dd
• 2 genes, Chromosome 1
1. RHD – codes for Rh D
2. RHCE – codes for Rh C and Rh E
• Highly immunogenic
• Rhesus antibody (IgG) can cross placenta
• Can cause haemolytic transfusion reactions and haemolytic disease of the fetus and newborn (HDFN)

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10
Q

Which chromosome codes for rhesus antigens

A

Chromosome 1

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11
Q

Haemolytic disease of the fetus/newborn (HDFN):

A

mother’s antibodies attacks baby’s erythrocytes
• Rh D sensitization most common cause
• Develop anti-Rh antibodies
• Severe fetal anaemia
• Hydrops fetalis (oedema)

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12
Q

Prevention of HDFN

A

• Detect mothers at risk
• Maternal fetal free DNA
• Anti D prophylaxis
• In-utero blood transfusion

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13
Q

Result of HDFN

A

• in-utero death
• Still-birth
• Brain damage
• Deafness
• Blindness

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14
Q

How many different systems of erythrocyte antigens are there

A

Over 400

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15
Q

Universal acceptor

A

AB: universal acceptor- 3%, no antibodies

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16
Q

Universal donor

A

O: universal donor, 45%, no antigens but has both anti-A and anti-B antibodies

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17
Q

Forward typing - ABO and RhD grouping

A

Patient RBCs- antigens
Commercial antibodies
+ve agglutination: same blood type as antibodies
positive test is thin red line on top of gel as blood has agglutinated due to reacting against specific reagents

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18
Q

Reverse typing - ABO and RhD grouping

A

Patient plasma- antibodies
Commercial antigens
+ve agglutination opposite blood type to antigens
testing patient’s serum with known RBC antigens

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19
Q

Cross-matching blood

A

• Units of blood deemed suitable chosen from stocks available:
• Either exact match (e.g. A+ for A+) OR
• “Compatible” blood (e.g. O- for A+)
• Serological test
• Prevent transfusion reactions

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20
Q

Indirect Antiglobulin (Coombs) test:

A

• blood grouping for ABO and Rhesus D
• Detects antibodies in patients serum

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21
Q

Direct antiglobulin (Coombs) test:

A

• detect antibodies on patient’s erythrocytes
• Used for: autoimmune haemolysis, transfusion reaction, haemolysis due to foetal/maternal group incompatibility

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22
Q

Homologous transfusion

A

anonymous donor

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23
Q

Autologous transfusion

A

self-donor eg planned surgery

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24
Q

Blood donation:

A

can donate whole blood or apheresis (blood removed and externally separated to collect plasma and platelets)- blood is mixed with calcium oxalate to prevent coagulation
• 17-65 year olds can be 1st time donors
• Donors screened at donation centres
• Questionnaire
Highlight those at risk of infectious/transmissible disease
Health, lifestyle, travel, medical history, medications
• Body weight (50 – 158 kg)

25
Q

What age do you have to be to donate blood

A

17-65

26
Q

What weight do you have to be to donate blood

A

50-158 kg

27
Q

Temporary Exclusion criteria for donating blood

A

• Travel
• Tattoos/Body piercings (3/4months)
• Lifestyle eg pregnant (6 months), anal sex with a new partner (3 months)

28
Q

Permanent exclusion criteria for donating blood

A

• Certain diseases eg HIV, hep B/C
• Received blood products or organ/tissue transplant since 1980
• Notified at risk of vCJD

29
Q

Tests done on donated blood

A

• Mandatory tests: Hep B, Hep C, Hep E, HIC, syphilis, HTLV, groups and antibodies
• Some: CMV, West Nile virus, malaria, trypanosoma

30
Q

Separation and storage of donated blood

A

• Whole blood donated into closed system bags
• Blood centrifuged to packed red cells, Buffy coat (white blood cells and platelets) and plasma
• Plasma only kept from MALE donors
• Plasma frozen (FFP) or processed to cryoprecipitate
• Red cells passed through leucodepletion filter (to remove white cells, especially lymphocytes as could cause GVHD) and suspended in additive
• Buffy coats pooled with matching ABO and D type and then leucode

31
Q

Why is plasma only kept from male donors

A

Female plasma is more antigenic

32
Q

Blood products: erythrocytes

A

• Stored at 4°C, shelf life 35 days
• Some units irradiated to eliminate risk of transfusion-associated graft vs host disease- kill left over white cells

33
Q

Indications and transfusion threshold for erythrocytes

A

Indications
• Severe anaemia (not purely iron deficiency)
Transfusion threshold
• Haemoglobin <70 g/L or <80 g/L + symptoms
• Transfuse 1 unit and recheck FBC (unless massive transfusion needed)
• Emergency stocks of O Rh D- available in certain hospital areas

34
Q

Blood products: platelets

A

• Most units pooled from 4 donations
• Some single-donor apheresis units
• Stored at 22°C with constant agitation (prevent clotting), 7 day shelf life

35
Q

Indications and transfusion thresholds for platelets

A

Indications
• Thrombocytopaenia (low platelet count) and bleeding
• Severe thrombocytopaenia < 10 due to marrow failure (150-450)
Transfusion threshold (NICE)
• <10 x 109 if asymptomatic and not bleeding
• <30 x 109 if minor bleeding
• <50 x 109 if significant bleeding
• <100 x 109 if critical site bleeding (brain, eye)
• Part of massive transfusion protocol
• ABO type still important (units contain ABO antibodies)

36
Q

Blood products: fresh frozen plasma

A

• From whole donations or apheresis
• Patients born > 1996 can only receive plasma from low vCJD risk
• Single donor packs have variable amounts of clotting factors. Pooled donations can be more standardised

37
Q

Indications for using fresh frozen plasma

A

Indications
• Multiple clotting factor deficiencies and bleeding (DIC)
• Some single clotting factor deficiencies where no concentrate available

38
Q

Blood products: cryoprecipitate

A

• Made by thawing FFP to 4°C and skimming off fibrinogen rich layer
• Used in DIC with bleeding, and in massive transfusion
• Therapeutic dose: 2 packs (each pooled from 5 plasma donations)

39
Q

Blood products: immunoglobulin

A

• Made from large pools of donor plasma
• Normal IVIg: Contains Ab to viruses common in population- Used to treat immune conditions e.g. ITP
• Specific IVIg: From selected patients- Known high AB levels to particular infections/conditions eg Anti D immunoglobulin used in pregnancy and VZV immunoglobulin in severe infection

40
Q

Blood products: Granulocytes

A

• Used very rarely
• Effectiveness controversial
• indication: Severely neutropaenic patients with life threatening bacterial infections
• Must be irradiated (to kill T cells)

41
Q

Blood products: factor concentrates

A

Single factor concentrates
• Factor VIII for severe haemophilia A (recombinant version – no risk of viral or prion transmission)
• Fibrinogen concentrate (Factor I)
Prothrombin complex concentrate (Beriplex/Octaplex)
• Multiple factors
• Rapid reversal of warfarin

42
Q

Safe delivery of blood

A

• Patient identification
• 2 sample rule
• Hand-written patient details
• Blood selected and serologically cross matched

43
Q

Indications for transfusions

A

• hypovolaemia due to blood loss
• Severe anaemia with inadequate oxygenation of tissues
• Anaemia- check B12 deficiency before considering, not indicated for iron or B12 deficiency

44
Q

Avoiding transfusions

A

• Optimise patients with planned surgical procedures pre-op
• Use of EPO-stimulating drugs in renal failure and in patients with cancers
• Intraoperative cell salvage
• IV iron for severe iron deficiency
• Some patients may tolerate lower haemoglobin concentrations and not require transfusion at all

45
Q

Early hazards of blood transfusions

A

• ABO incompatibility reaction
• Fluid overload- pulmonary oedema
• Febrile reaction- antigens target donor antigens, can cause life-threatening respiratory failure
• Bacterial and malarial infection

46
Q

Late hazards of blood transfusions

A

• rhesus D and other antibody sensitisation
• Delayed transfusion reaction
• Viral infection, hep B/C or HIV
• Prion infection
• Iron overload resulting in cardiac, hepatic and endocrine damage

47
Q

Haemolytic reactions

A

• ABO incompatibility
Rapid intravascular haemolysis
Cytokine release
Acute renal failure and shock
DIC
Can be rapidly fatal
• Treatment
STOP transfusion immediately
Fluid resuscitate
• Can be acute or delayed (>24 hrs)
• Must be reported to SHOT (serious hazards of transfusion)

48
Q

Bacterial contamination of blood

A

• Most commonly with platelets (still v. rare)
• Symptoms very soon after transfusion starts
Fever and rigors
Hypotension
Shock
• Inspection of unit may show abnormal colouration/cloudiness

49
Q

Transfusion-related lung injury

A

• antibody in donor blood reacts with recipient’s pulmonary epithelium/neutrophils
• Inflammation causes plasma to leak into alveoli
• Symptoms:
Shortness of breath
Cough with frothy sputum
Hypotension
Fevers
• Supportive treatment

50
Q

Transfusion-associated circulatory overload (TACO)

A

• Acute/worsening pulmonary oedema within 6 hours of transfusion
• Older patients more at risk
• Symptoms:
Respiratory distress
Evidence of positive fluid balance
Raised blood pressure
• Careful assessment of transfusion need and limiting amount can help avoid.

51
Q

Alternatives to transfusion

A

Treat anaemia pre-op
Stop anti-platelet and anti-coagulant drugs
Operative erythropoietin to stimulate RBC production

52
Q

When are first true ABO antibodies produced

A

> 3 months

53
Q

Age of maximal titre of ABO antibodies

A

5-10 years

54
Q

What causes the titre of ABO antibodies to decrease

A

Aging

55
Q

Haemolytic disease of the foetus and newborn (HDFN) process

A
  1. RhD -ve mum and RhD +ve dad: RhD is dominant
  2. RhD +ve baby no.1 ——-> sensitisation (primary immune response)——-> mum makes IgM anti-D antibodies (can’t cross placenta) then IgG anti-D antibodies
  3. RhD +ve baby no.2 ——-> secondary immune response——> mum makes lots of IgG anti-D antibodies which cross placenta. Attack RhD antigens on fetal RBCs ——> haemolysis——-> anaemia
56
Q

How to prevent sensitisation for HDFN

A

Anti-D injections

57
Q

Universal blood donor

A

O-

58
Q

Group and save

A

Determine blood group and check plasma for antibodies from previous transfusions
Separate and save plasma

CVR (22 decks)

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