microcytic anaemia Flashcards
what is it?
Hb is synthesised in the cytoplasm, to make Hb you need all the building blocks
• One of these is lacking in microcytic anaemias
• The nuclear machinery is intact however- so cells can keep dividing
• As a result the cells are microcytic (small)
• And as the contain little Hb they are hypochromic (lacking in colour)
what causes it?
haem deficiency globin deficiency (thalassaemia - trait, intermedia, major)
what causes haem deficiency
lack of iron for erythropoiesis
- iron deficiency (low body iron)
- some cases of anaemia of chronic disease (normal body iron but lack of available iron) - most normocytic
problems in porphyrin synthesis
- lead poisoning
- congenital sideroblastic anaemias
measurements of iron status
Functional iron - Haemoglobin Transported iron o Serum iron o Transferrin o Transferrin saturation Storage iron o Serum ferritin
how can iron deficiency be confirmed
combination of anaemia (decreased functional iron)
and
reduced storage iron (low serum ferritin)
if iron is deficient a cause MUST be found
causes of iron deficiency
diet and malabsorption - iron absorption can be increased by iron supplements
chronic blood loss
- menorrhagia
- GI (tumours, ulcers, NSAIDs)
- haematuria
- menstrual blood loss
(iron absorption isn’t massive from the diet so iron status precarious, heavy menstrual blood loss >60ml)
affect of iron deficiency anaemia on the system
• Exhaustion of iron stores (ferritin falls)
• Iron deficient erythropoiesis (MCV falls)
• Microcytic Anaemia develops (may be relative not absolute microcytosis)
• Epithelial changes (effects elsewhere)
o skin
o koilonychia
o angular chelitis
how is iron deficiency anaemia managed?
find and address cause so no recurrence
improve iron intake - review diet, improve gastric acidity
review other medication e.g. anticoagulants and PPIs
restoration of iron stores depends on Hb being back to normal
rise in Hb is limited by the ability of marrow to upregulate rbc production (if marrow is healthy Hb conc. can increase by 7-10g/l per week if well supplied with iron but there will be less of a rise if other issues such as ongoing blood loss)
what iron supplements are given?
oral iron preparations
parenteral (IV) iron preparations
why choose oral preparations?
oral preps are cheap and effective can be poorly tolerated
iron irritates the gut but appears to be dose dependent
100-200mg of elemental iron is typically given although 65mg daily may be sufficient. Larger doses may give more side effects and little additional benefit
Ferrous sulphate, ferrous fumarate and ferrous gluconate are available in tablet form
- Sodium feredetate (sytron) liquid prep with lower iron concentration used in paediatrics
what are the side effects of oral iron preparations
Choice of prep determined by incidence of side effects and cost
- Side effects principally gastrointestinal
- Constipation, nausea, vomiting, abdo pains
- Dark stools
- Can result in poor compliance
when are parenteral (IV) iron preparations used
only consider when oral is unsuccessful
- poor tolerance or compliance of oral, malabsorption issues, specific situations such as renal anaemia
better and faster response than well tolerated oral iron
concerns re anaphylaxis, given in hospital because IV, more expensive but more reliable delivery of iron
dose of parenteral (IV) iron preps
o Dose calculated on the degree of anaemia and patient weight.
o May be given in a split dose over several visits
what is the follow up
- Assess response after period of treatment usually 4-6 weeks
- Clinical response and lab response – Rise in Hb, mcv and retics
- Typically need to continue for 2-3 months to replenish stores
if there has been a poor response what should you consider?
o Compliance – Reduce frequency, switch to lower iron containing preparation, consider parenteral route
o Ongoing blood loss
o Malabsoption rarely a cause
