Flashcards in Anaemia Deck (18):
Function of erythrocytes and their formation and destruction?
Haemopoetic stem cells - GF (erythropoietin) encourage differentiation and development.
Aged RBCs engulfed by macrophages in reticulendothelial system of liver and spleen
What is the Haemocrit?
volume of RBCs in blood as a percentage of total blood volume (approx 45%)
Structure of Hb
4 x globin subunits (2 pairs)...each bound to a haem which contains ferrous Fe++ which binds O2.
4O2 molecules can bind altogether
reduced concentration of Hb in the blood
Causes and symptoms of anaemia
Menstruation, pregnancy, dietary deficiency, bone marrow supression, excessive destruction of RBCs (haemolytic anaemia)
What is microlytic anemia?
small RBCs, low Hb, iron deficiency
What is macrolytic anaemia?
large, fragile, deformed RBCs, few in number, vit B12 and folic acid deficiency
What is normolytic anaemia?
normal size RBCs, few in number, bone marrow supression
What is the choice of drugs dependant on?
The underlying cause of the anaemia
Iron...normal levels, loss and absorption..how is absorption enhanced/decreased?
70kg man...4g or iron...1.8g in Hb...800mg in liver, spleen and bone marrow.
1-2 mg lost per day Recycled, levels changed by changes in absorption. Iron in meat and fish = heam iron...best for absorption. Veg and pulses...non-haem iron.
Ascorbic acid - increase absorption...fe+++ reduced to fe++...and form soluble iron-ascorbate complexes
Tetracycline...decrease absorption. Form insoluble complexes. Decrease absorption of iron and antibiotic
Most common causes of iron deficiency?
Excess blood loss - mestrutation, GI bleed
Increased utilisation - pregnancy
Poor absorption - tetracycline, GI disease
Describe iron absorption
In duodenum, ferric iron is converted by ferric reductase to ferrous iron. Fe++ is then transported via the divalent metal transported 1 to the endothelial cells. Ferrous iron is then either converted to ferric iron and stored as ferritin (water soluble, stores 4500) or is transported to the blood along with haem iron which has been converted by haem oxidase to ferrous iron. Ferroportin transports Fe++ to the blood where is converted to ferric iron and then 2 fe+++ are added to apotransferrin to form transferrin which is moved to the bone marrow.
Oral iron preparations - doses and side effects
Ferrous sulphate (200mg table with 65mg of iron) or ferrous gluconate
Side effects are dose related..mild nausea, diarrhoea or abdominal cramps
Acute iron toxicity...when does it occur, symptoms and how is it treated?
Occurs in overdose
Severe gastritis with haemorrhaging, vommiting, diarrhoea and potential circulatory collapse.
Treated with iron chelators - desferrioxamine (binds excess iron and excretes it in urine).
Role of VitB12 and Folic acid
DNA synthesis and cell proliferation therefore deficiency noticed as RBCs have a rapid turnover. Results in macrolytic anaemia.
Vit B12 deficiency...leads to?
Intake of Vit B12?
leads to neurological disorders, usually due to lack of intrinsic factor (required for vit B12 absorption) - pernicious anaemia
liver eggs dairy
injected as hydroxocobalamin
Folic acid (vit B9) deficiency?
Lack of intake during periods of high demand
Found in green veg, liver, fruit, yeast - need 200mg a day
enters cells as 5methylFH4