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Yr 4 - Paediatrics > Haem: Anaemia > Flashcards

Haem: Anaemia Flashcards

1
Q

Role of haemoglobin (Hb)?

A

Haemoglobin is the molecule responsible for transporting oxygen around the body. It is found in RBCs.

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2
Q

What is Hb formed of (adult vs foetal)?

A

Haemoglobin is formed of four protein subunits. These four subunits are made of two pairs of subunits.

HbA –> 2x alpha and 2x beta

HbF –> 2x alpha and 2x gamma

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3
Q

How does the structure of HbF affects its affinity for oxygen?

A

HbF has a greater affinity to O2 than HbA.

I.e. O2 binds to HbF more easily and is more reluctant to let go.

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4
Q

Why is it important that HbF has a stronger affinity for O2 than HbA?

A

As HbF needs to ‘steal’ oxygen away from HbA when nearby in the placenta.

If the fetal and maternal haemoglobin had the same affinity for oxygen, there would be no incentive for the oxygen to switch from the maternal blood to fetal blood.

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5
Q

What is found on the x-axis on an oxygen dissociation curve?

A

Partial pressure of O2 (i.e. how much oxygen is crammed into a space).

The higher the partial pressure, the more oxygen is in the area.

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6
Q

What is found on the y-axis on an oxygen dissociation curve?

A

Saturation of Hb with O2.

This is how “full” the haemoglobin molecule is.

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7
Q

Oxygen dissociation curve for HbA vs HbF?

A

Google this.

HbA requires a higher partial pressure of oxygen for the molecule to fill with oxygen compared with HbF.

I.e. curve for HbA is further to the right.

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8
Q

Describe transition from HbF to HbA

A

From 32 to 36 weeks gestation, production of HbF decreases. At the same time HbA is produced in greater quantities.

Over time there is a gradual transition from HbF to HbA.

At birth, around half the haemoglobin produced is HbF and half is HbA.

By 6 months of age, very little fetal haemoglobin is produced.

Eventually, RBCs contain entirely HbA.

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9
Q

Why is HbF not affected by sickle cell disease?

A

In sickle cell, mutation of the beta subunit results in the sickle shape of RBCs.

HbF does not lead to sickling of red blood cells because there is no beta subunit in the structure.

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10
Q

Hydroxycarbamide is a treatment in patients with sickle cell anaemia.

How does this work?

A

Hydroxycarbamide increases the production of HbF in patients with sickle cell anaemia.

This has a protective effect against sickle cell crises and acute chest syndrome.

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11
Q

What is the most common cause of anaemia in infancy?

A

Physiologic anaemia of infancy

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12
Q

Give some causes of anaemia in infancy

A

1) Physiologic anaemia of infancy

2) Anaemia of prematurity

3) Blood loss

4) Haemolysis

5) Twin-twin transfusion: where blood is unequally distributed between twins that share a placenta

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13
Q

Haemolysis is a common cause of anaemia in infancy.

Give 3 causes of haemolysis in a neonate

A

1) Haemolytic disease of the newborn (ABO or rhesus incompatibility)

2) Hereditary spherocytosis

3) G6PD deficiency

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14
Q

When is there a normal dip in Hb in healthy term babies?

A

Around 6-9 weeks of age

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15
Q

What causes a normal Hb dip in healthy term babies around 6-9 weeks of age?

A

1) High oxygen delivery to the tissues caused by the high Hb levels at birth cause negative feedback.

2) Production of EPO by the kidneys is suppressed.

3) Subsequently there is reduced production of Hb by the bone marrow.

i.e. The high oxygen results in lower Hb production.

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16
Q

What is anaemia of prematurity?

A

Premature neonates are much more likely to become significantly anaemic during the first few weeks of life compared with term infants.

The more premature the infant, the more likely they are to require one or more transfusions for anaemia.

This becomes more likely if they are unwell at birth, particularly with neonatal sepsis.

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17
Q

Why are premature infants more at risk of anaemia?

A

1) Less time in utero receiving iron from the mother

2) RBC creation cannot keep up with the rapid growth in the first few weeks

3) Reduced EPO levels

4) Blood tests remove a significant portion of their circulating volume

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18
Q

What is haemolytic disease of the newborn (HDN)?

A

A cause of haemolysis and jaundice in the neonate.

It is caused by incompatibility between the rhesus antigens on the surface of the RBCs of the mother and fetus.

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19
Q

What test can be used to check for immune haemolytic anaemia?

A

A direct Coombs test (DCT) - this will be positive in HDN.

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20
Q

What are the 2 key causes of anaemia in older children?

A

1) Iron deficiency anaemia secondary to dietary insufficiency (most common)

2) Blood loss, most frequently from menstruation in older girls

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21
Q

Give some rarer causes of anaemia in older children

A

1) Sickle cell anaemia

2) Thalassaemia

3) Leukaemia

4) Hereditary spherocytosis

5) Hereditary eliptocytosis

6) Sideroblastic anaemia

22
Q

Worldwide, what is a common cause of blood loss causing chronic anaemia & iron deficiency?

A

Helminth infection, with roundworms, hookworms or whipworms.

This can be very common in developing countries and those living in poverty.

23
Q

Treatment of helminth infection?

A

With a single dose of albendazole or mebendazole.

24
Q

Anaemia is initially subdivided into three main categories based on the size of the RBC (the MCV).

What are the 3 types?

A

1) Microcytic anaemia: low MCV indicating small RBCs

2) Normocytic: normal MCV indicating normal sized RBCs

3) Macrocytic: large MCV indicating large RBCs

25
Q

A helpful mnemonic for understanding the causes of microcytic anaemia is TAILS.

What are the causes?

A

T - thalassaemia
A - anaemia of chronic disease
I - iron deficiency
L - lead poisoning
S - sideroblastic anaemia

26
Q

Macrocytic anaemia can be megaloblastic or normoblastic.

What is megaloblastic anaemia the result of?

A

Impaired DNA synthesis preventing the cell from dividing normally.

Rather than dividing it keeps growing into a large, abnormal cell.

This is caused by a vitamin deficiency.

27
Q

What are the 2 causes of megaloblastic anaemia?

A

1) B12 deficiency

2) Folate deficiency

28
Q

Give some causes of normoblastic macrocytic anaemia

A

1) Alcohol

2) Reticulocytosis (usually from haemolytic anaemia or blood loss)

3) Hypothyroidism

4) Liver disease

5) Drugs such as azathioprine

29
Q

What type of anaemia does koilonychia (spoon shaped nails) indicate?

A

iron deficiency

30
Q

What type of anaemia does atrophic glossitis indicate?

A

iron deficiency

31
Q

What is atrophic glossitis?

A

a smooth tongue due to atrophy of the papillae and can indicate iron deficiency

32
Q

Investigations in anaemia?

A
  • Full blood count for haemoglobin and MCV
  • Blood film
  • Reticulocyte count
  • Ferritin (low iron deficiency)
  • B12 and folate
  • Bilirubin (raised in haemolysis)
  • Direct Coombs test (autoimmune haemolytic anaemia)
  • Haemoglobin electrophoresis (haemoglobinopathies)
33
Q

What does a high number of reticulocytes indicate?

A

This usually indicates the anaemia is due to haemolysis or blood loss.

Indicates active production of RBCs to replace lost cells.

34
Q

What is the most common cause of iron deficiency anaemia in children?

A

Dietary insufficiency

35
Q

Give 3 causes of iron deficiency anaemia in children

A

1) Dietary insufficiency

2) Loss of iron, for example in heavy menstruation

3) Inadequate iron absorption, for example in Crohn’s disease

36
Q

Where is iron mainly absorbed?

A

Duodenum & jejunum

37
Q

What does iron require for absorption?

A

It requires the acid from the stomach to keep the iron in the soluble ferrous (Fe2+) form.

When there is less acid in the stomach, it changes to the insoluble ferric (Fe3+) form.

38
Q

What medications can interfere with iron absorption?

A

Medications that reduce the stomach acid, such as PPIs (lansoprazole and omeprazole)

39
Q

What conditions can affect iron absorption?

A

Conditions that result in inflammation of the duodenum or jejunum e.g. coeliac disease or Crohn’s disease.

40
Q

How does iron travel around the blood?

A

As Fe3+ bound to transferrin (carrier protein).

41
Q

Define total iron binding capacity (TIBC)?

A

The total space on the transferrin molecules for the iron to bind.

TIBC is directly related to the amount of transferrin in the blood.

Transferrin Saturation = Serum Iron / Total Iron Binding Capacity

42
Q

What form does iron take when it is deposited and stored in cells?

A

Ferritin

43
Q

Ferritin is an acute phase reactant. What does this mean?

A

Extra ferritin is released from cells when there is inflammation, e.g. infection or cancer.

44
Q

Why is high ferritin difficult to interpret?

A

It is likely to be related to inflammation rather than iron overload.

45
Q

Why is serum iron not a very useful measure on its own?

A

Serum iron varies significantly throughout the day, with higher levels in the morning and after eating iron containing meals.

46
Q

Why is a fasting sample better for iron studies?

A

Iron levels/transferrin saturation can increase shortly after eating a meal rich in iron or taking iron supplements, so a fasting sample is better.

47
Q

Two things can increase the values in iron studies (except TIBC, which will be low), giving the impression of iron overload.

What are these two things?

A

1) Supplementation with iron

2) Acute liver damage (lots of iron is stored in the liver)

48
Q

What iron supplementation is usually given in iron deficiency anaemia?

A

Ferrous sulphate or ferrous fumarate

49
Q

Side effects of oral iron?

A

Constipation & black coloured stools

50
Q

When is oral iron unsuitable?

A

It is unsuitable where malabsorption is the cause of the anaemia.

51
Q

Why are blood transfusions for anaemia rarely necessary in children?

A

Children are generally able to tolerate a low haemoglobin well and can be given time to correct their anaemia.

52
Q
A

Yr 4 - Paediatrics (78 decks)

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