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2.2 Transfusion Science > Haemolytic Disease of The Newborne > Flashcards

Haemolytic Disease of The Newborne Flashcards

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1
Q

Who is responsible for discovered the process behind HDN

A

Levine and Stetson

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2
Q

When did Levine and Stetson first suggest HDN

A

1939

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3
Q

What happens in HDN
(3)

A

Foetal/maternal blood group incompatibility

Maternal transfer of IgG antibodies against foetal rbc antigens

Results in haemolysis of foetal rbcs

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4
Q

How does the mother become sensitised against the foetus
(3)

A

Small amount of foetal blood enters mothers circulation during first pregnancy

Due to foetal bleed

igG cross the placenta

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5
Q

How is HDN treated
(3)

A

As long as the foetus gets to birth then the child can be treated -> from birth no more antibodies against foetal cells will enter circulation

Baby can die even after birth if there is no intervention

Photolight therapy is often used -> involves using UV light to treat haemolysis in babies -> breaks down bilirubin in jaundiced babies

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6
Q

What antibodies are responsible for HDN

A

Anti-D
Anti-c
Anti-K

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7
Q

What is the most common cause of HDN

A

Anti-D

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8
Q

When might there be immunisation against the foetal cells in the first pregnancy
(3)

A

Due to foetal cells entering the maternal circulation

Foetal maternal haemorrhage

But mother’s antibody titre is usually too low in the first pregnancy to affect the foetus

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9
Q

What blood do we give to women of child bearing years

A

D- and K- blood to prevent antibody formation prior to pregnancy

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10
Q

What is considered the danger period of HDN

A

Soon after the birth of a RhD positive baby

72 hours after birth

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11
Q

List the steps in HDN
(7)

A

Rh negative woman before pregnancy

Pregnancy with Rh-positive fetus

Placental separation

maternal sensitisation to Rh positive blood

Maternal development of anti-Rh antibodies

Anti-Rh antibody to foetal Rh-positive red blood cells

Haemolysis of foetal RBCs

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12
Q

What are the three steps to foetal rbcs destruction in HDN
(5)

A

Foetal rbcs are coated with antibodies

Coated rbcs are removed by splenic macrophages

Foetal haematopoietic tissues increase production of rbcs

Premature release of NRBCs from bone marrow

Severe anaemia with oedema

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13
Q

What are the other names for HDN

A

Erythroblastosis foetalis

Hydrops foetalis

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14
Q

Why is HDN also known as erythroblastosis foetalis

A

It results in the premature release of NRBCs from bone marrow

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15
Q

Why is HDN also known as hydrops foetalis

A

It causes oedema through leakage of fluid into extravascular spaces

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16
Q

What are the clinical effects of HDN on the foetus
(4)

A

Excess breakdown of Hb which leads to raised bilirubin

After birth mother’s circulation no longer removes bilirubin so it builds up in fatty tissue e.g. nervous tissue e.g brain -> kernicterus

Albumin which binds bilirubin is also low in newborns

Anaemia may result in organ failure if severe

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17
Q

What is kernicterus

A

Build up of bilirubin in the brain

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18
Q

Write a note on kernicterus
(6)

A

25-30% of affected foetus are born with pallor

Progressive jaundice ensues

Brain damage occurs within 3-4 days

Death occurs in 90% of patients via respiratory arrest

Surviving 10% have severe brain damage

This rarely happens in first world countries

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19
Q

Why does bilirubin target the brain
(4)

A

Brain composed of nervous tissue

Nerves insulated with myelin

Myelin is a fatty tissue

bilirubin has an affinity for fat

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20
Q

What happens when bilirubin binds to myelin of nerves
(3)

A

Bilirubin impregnates the myelin sheet

Nerve conduction is impaired -> results in short circuits -> nerves will short

Can cause cardiac arrest

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21
Q

What are prenatal tests

A

Test to identify women at risk of HDFN

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22
Q

What are the initial tests carried out on women at risk of HDFN
(5)

A

ABO/D test
Weak D test (optional)
Screening for IgG antibodies
Further igG antibody identification if screen positive
Antibody titration for IgG antibodies to establish baseline

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23
Q

What follow up tests are carried out on women at risk of HDFN is igG positive

A

Selected reagent red cell panel is run to exclude other clinically significant antibodies

Antibody titration in parallel with initial sample at 2-4 week intervals

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24
Q

What testing is carried out of pregnant women at 26-28 weeks pregnant

A

Confirm D typing -> can type foetus from mothers blood

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25
Q

What tests are done when a pregnant woman first visits the hospital
(3)

A

ABO and Rh group is checked

Antibody screening

Identifying antibodies as IgG or IgM

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26
Q

What tests are done when a pregnant woman is at 28 weeks
(4)

A

Titration/Quantification of Anti-D if present

Blood grouping of partner -> are they DD or Dd

Blood grouping of foetus

Amniocentesis to measure bilirubin of foetus

Chorionic villus sampling

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27
Q

What is chorionic villus sampling
(2)

A

Blood sample taken from chorionic villus to measure haemoglobin to see if foetus is suffering from anaemia

This is not really done anymore -> as there is a 1% chance of spontaneous abortion

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28
Q

How do we measure bilirubin of foetus now?

A

Use amniotic fluid

Use cell free foetal DNA

Doppler Ultrasound used now

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29
Q

What is the chorionic vililus

A

The region where the placenta binds to the foetus

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30
Q

what is cffDNA

A

Cell free foetal DNA

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31
Q

What does measuring cffDNA give us
(2)

A

We PCR the D- mother’s blood for RhD DNA

If RhD DNA present then it must be from the foetus therefore we can type the foetus as RhD+

32
Q

What is a Doppler ultrasound
(2)

A

Colour Doppler ultrasonography

Used to detect foetal anaemia

33
Q

How does Doppler ultrasound identify anaemia

A

Detects increased cardiac output and low blood viscosity

Severity of anaemia is determined by evaluating the peak systolic velocity in the middle cerebral artery

34
Q

What is amniocentesis
(3)

A

Amniotic fluid is scanned spectrophotometrically for 350 to 700nm

A change in optical density (delta OD) above baseline (450nm) is a measure of bilirubin

The delta OD is plotted on a Liley Graph

35
Q

How is a Liley graph used to pick up bilirubin
(3)

A

Upper zone (zone 3): indicates severe HDFN

Middle zone (zone 2): moderate disease

Lower zone (zone 1): mild disease

36
Q

How is HDN prevented
(2)

A

Give mother anti-D antibodies before she can be stimulated to produce her own antibodies

When a D negative mother gives birth to a D positive baby she would be given these anti-D antibodies within 72 hours

37
Q

Where do we get anti-D antibodies for transfusion from?
(3)

A

We haven’t been able to produce a monoclonal anti-D yet so instead we use a human blood product

They gave D positive blood to D negative men

Good responders who produced lots of anti-D antibodies were selected to donate plasma

38
Q

When is anti-D given to pregnant women

A

Given at 28 weeks

Given in the 72 hours after birth

39
Q

Why would we fail to prevent HDN
(5)

A

Anti-D not given

Anti-D not given in the 72 hours after birth of baby

Silent foetal maternal haemorrhage -> possibility that anti-D will run out by delivery

Incorrect timing of Routine antenatal anti-D prophylaxis (RAADP)

Another antigen causes HDN e.g. anti-Fy(a)

40
Q

What is RAADP?

A

Routine antenatal anti-D prophylaxis

41
Q

What is Routine antenatal anti-D prophylaxis (RAADP)?

A

Administration of RhD+ blood to RhD- pregnant women

42
Q

What’s the one issue with RAADP

A

We can’t tell the difference between anti-D from mother or anti-D administered

43
Q

Give the name of one of the anti-D products used regularly

A

Rhophylac

44
Q

What Rh Igs are not indicated -> in what scenarios does anti-D not need to be administered

A

Patients who are already sensitised

Weak D’s

If the infant is Rh negative

For women not capable of child bearing age

45
Q

What is FMH?

A

Foeto-maternal haemorrhage

46
Q

List the methods for estimating FMH
(3)

A

Kleihauer Betke test

Rosetting technique

Flow cytometry

47
Q

What is the Kleihauer Betke test
(2)

A

Kleihauer Betke acid elution technique

This test relies on the resistance of HbF to be eluted(removed) out of the rbc by an acid buffer solution

48
Q

How is the Kleihauer Betke Test (KEB test) carried out?
(6)

A

Mothers blood with EDTA

Blood film

Dip in acid

Adult haemoglobin is acid soluble but HbF is not

Only foetal cells are left on the blood film

Count the foetal cells to determine how many cells are in mothers circulation and therefore how big of a bleed it was

49
Q

What is the rosetting technique
(3)

A

A technique used to demonstrate small numbers of D positive cells in a predominantly D negative population

Detects FMH of approximately 10mls

This isn’t really carried out in Ireland anymore but is still done in the US

50
Q

How is rosetting carried out

A

Count the rosettes seen in a blood film

D-positive cells will have rosettes of cells around them

51
Q

How is flow cytometry used to estimate FMH

A

Use flourescein labelled anti-D antibody

52
Q

What is a DAT

A

Direct Antiglobulin test

53
Q

What is a direct antiglobulin test
(3)

A

DAT diagnoses the presence of antibodies on cells

Cells shouldn’t normally be coated in antibodies

There will be maternal antibodies on foetal cells if there has been a bleed -> these indicate that the rbcs are being destroyed

54
Q

Why might there be antibodies on cells
(4)

A

Occurs in pregnancy

Occurs in autoimmune reaction

Occurs in transfusion

Used for demonstration of in vivo sensitisation of red cells with antibodies

55
Q

How is a DAT carried out
(4)

A

Cells are coated with antibodies in vivo

We wash the cells to remove unbound globulins

We add anti-human globulin (AHG) which promotes agglutination after centrifugation

If there has been in vivo sensitisation then the cells will clump after addition of AHG

56
Q

What is an indirect antiglobulin test
(3)

A

Serum with specific antibody mixed with reagent red cells

Washed 3x after incubation to remove unbound globulins

Anti-human globulin is added to promote agglutination on centrifugation

57
Q

What is the direct antiglobulin test also called?

A

Direct Coombs test

58
Q

How do we carry out a direct antiglobulin test
(4)

A

Blood sample taken from patient with haemolytic anaemia

Antibodies are shown attached to antigens on the RBC surface

The patients washed RBCs are incubated with antihuman antibodies (Coombs reagent)

RBCs agglutinate: antihuman antibodies form links between RBCs by binding to the human antibodies on the RBCs

59
Q

How do we carry out an indirect coombs test/antiglobulin test
(5)

A

Recipient’s serum contains antibodies

Donors blood sample is added to the tube with serum

Recipient’s Ig’s that target the donors red blood cells form antibody-antigen complexes

Anti-human Ig’s are added to the solution

Agglutination of red blood cells occurs, because human Ig’s are attached to rbcs

60
Q

How do we treat affected babies
(5)

A

We measure anti D and anti C to see how severe the disease is

Prenatal:
- Intra-uterine transfusions can be done
- Plasma exchange

Postnatal:
- exchange transfusions
- phototherapy to break down bilirubin pigment

61
Q

What is considered mild, moderate and severe anti-D ?

A

mild < 4

Moderate = 4 -> 15

Severe = 15+

62
Q

What is considered mild, moderate and severe anti c?

A

Mild = < 8
Moderate to severe = 8+

63
Q

What is an intra-uterine transfusion
(5)

A

Transfusion guided by ultrasound via the placenta

Highly concentrated rbc pack is used

1 in 100 risk of spontaneous abortion

Transfuse about 20 units a year

Medical scientists will actually come out of the lab and see the patient for this

64
Q

What is plasma exchange

A

This is done on the mother -> removes anti-D antibodies from mothers circulation

65
Q

What tests may be done on a HDN baby

A

Haemoglobin

Bilirubin

DAT

66
Q

How is Hb affected by HDN?

A

Babies born will have low Hb

67
Q

How is bilirubin affected by HDN?

A

babies born will have raised bilirubin

68
Q

What will a DAT reveal in HDN babies

A

May reveal babies have in vivo coating of red cells with maternal antibody

69
Q

Why might an exchange transfusion be carried out on a baby

A

Take out some of the babies blood and give D negative blood -> only transfuse very small volumes approx 50mls

70
Q

How do intrauterine transfusions work

A

Foetus receives transfusion through the umbilical vein in the placenta

71
Q

What blood is given to newbornes in need of transfusion
(7)

A

Blood must be less than 5 days old

Must be packed red cells

Must be leucocyte depleted

Must be irradiated

Must be from a cytomegalovirus negative donor

Must be a small volume - approx 50 mls

Must be HbS negative

72
Q

Why must blood be less than 5 days old to be given to a baby
(4)

A

Stored blood is fine for an adult

But rbcs leak potassium when in storage

High potassium can cause heart attack in newborns

New borns aren’t able to regulate salts and electrolytes as easy as adults

73
Q

Why are rbc packs for babies leucocyte depleted

A

Leucocytes will continue to live in the patient if their body can’t kill them

Leucocytes will colonise baby’s circulation

74
Q

Why are rbc packs irradiated
(2)

A

This ensures no nuclear material -> leukocytes can be found in the newborn

If this is not done Graft versus host disease will result which is nearly always fatal in newborns

75
Q

What is graft versus host disease
(2)

A

White blood cells of the donor’s immune system which remain within the donated tissue recognize the recipient as foreign.

The white blood cells present within the transplanted tissue then attack the recipient’s body’s cells

76
Q

What happens if a group O mother has a group A or B baby
(7)

A

Disease state usually mild

1st pregnancy can be affected -> already have anti-A or anti-B antibodies

Anti A or Anti B antibodies are IgG and can cross the placenta

Mild disease as ABO antigens are mildly expressed by the foetus

DAT will be positive

Phototherapy can be used to treat

Transfusion can be given if required

77
Q

Why might a premature baby need a transfusion
(3)

A

Premature babies need a lot of monitoring so a lot of tests are carried out

Even though only small volumes of blood are taken this all adds up if baby is being tested multiple times a day

Baby might need a transfusion to top up

2.2 Transfusion Science (22 decks)

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