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Blood Groups And Blood Transfusions Flashcards

(58 cards)

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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:

Study These Flashcards
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
What age do you have to be to donate blood
17-65
26
What weight do you have to be to donate blood
50-158 kg
27
Temporary Exclusion criteria for donating blood
• Travel • Tattoos/Body piercings (3/4months) • Lifestyle eg pregnant (6 months), anal sex with a new partner (3 months)
28
Permanent exclusion criteria for donating blood
• Certain diseases eg HIV, hep B/C • Received blood products or organ/tissue transplant since 1980 • Notified at risk of vCJD
29
Tests done on donated blood
• Mandatory tests: Hep B, Hep C, Hep E, HIC, syphilis, HTLV, groups and antibodies • Some: CMV, West Nile virus, malaria, trypanosoma
30
Separation and storage of donated blood
• 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
Why is plasma only kept from male donors
Female plasma is more antigenic
32
Blood products: erythrocytes
• 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
Indications and transfusion threshold for erythrocytes
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
Blood products: platelets
• 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
Indications and transfusion thresholds for platelets
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
Blood products: fresh frozen plasma
• 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
Indications for using fresh frozen plasma
Indications • Multiple clotting factor deficiencies and bleeding (DIC) • Some single clotting factor deficiencies where no concentrate available
38
Blood products: cryoprecipitate
• 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
Blood products: immunoglobulin
• 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
Blood products: Granulocytes
• Used very rarely • Effectiveness controversial • indication: Severely neutropaenic patients with life threatening bacterial infections • Must be irradiated (to kill T cells)
41
Blood products: factor concentrates
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
Safe delivery of blood
• Patient identification • 2 sample rule • Hand-written patient details • Blood selected and serologically cross matched
43
Indications for transfusions
• 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
Avoiding transfusions
• 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
Early hazards of blood transfusions
• ABO incompatibility reaction • Fluid overload- pulmonary oedema • Febrile reaction- antigens target donor antigens, can cause life-threatening respiratory failure • Bacterial and malarial infection
46
Late hazards of blood transfusions
• 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
Haemolytic reactions
• 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
Bacterial contamination of blood
• 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
Transfusion-related lung injury
• 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
Transfusion-associated circulatory overload (TACO)
• 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
Alternatives to transfusion
Treat anaemia pre-op Stop anti-platelet and anti-coagulant drugs Operative erythropoietin to stimulate RBC production
52
When are first true ABO antibodies produced
>3 months
53
Age of maximal titre of ABO antibodies
5-10 years
54
What causes the titre of ABO antibodies to decrease
Aging
55
Haemolytic disease of the foetus and newborn (HDFN) process
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
How to prevent sensitisation for HDFN
Anti-D injections
57
Universal blood donor
O-
58
Group and save
Determine blood group and check plasma for antibodies from previous transfusions Separate and save plasma

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