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What is anaemia?
A reduction in the erythrocyte number and/or the haemoglobin concentration i.e. decreased RBC, HCT/PVC and/or Hb
What are some of the clinical features of acute anaemia?
- Muscular weakness
- Subnormal temperature
What are some of the clinical features of chronic anaemia?
- Exercise intolerance
- Cardiac murmur
How do you tell if the anaemia is regenerative?
- Take a blood smear. It anaemia is regenerative you will see:
- Increased reticulocytes in the blood (but not in horses)
- Cells will be macrocytic (increase in MCV) and hypo chromic (decrease in MCH, MCHC)
- Increased polychromasia (describes the blue/grey colour of reticulocytes) / increased anyocytosis (differing in cell size)
- Sometimes there are nucleated red cells
- Basophilic stippling (cattle) - lots of little dots on reticulocytes
Haemorrhagic anaemia is caused by blood loss. What causes blood loss that is:
- a) trauma or surgical procedures
- b) bleeding from ulcers, neoplasms, parasites
- c) eg rat bait
What would you expect to find in blood from a patient with haemorhhagic anaemia?
- The blood findings would be normal in the first couple of days after the haemorrhage because it takes the body a while to adapt
- After a few days the RBC count would decrease and plasma protein concentration would decrease (as fluid moves from the tissues to the blood so more fluid = lower protein concentration).
- The blood smear would indicate:
- H-J bodies - nuclear remnants inside RBCs
- Thrombocytosis - increase number of platelets
- Neutrophilia - increased number of neutrophils
What is the difference, with regards to iron, between haemorrhagic and haemolytic anaemia?
In haemorrhagic anaemia RBCs are being lost through a wound so therefore iron is being lost. This means cells will be hypochromic. Whereas in haemolytic anaemia RBCs are lysing within the body so no iron is being lost, it is simply recycled. This means cells will be normochromic.
How are RBCs destroyed in haemolytic anaemia?
- Extravascular lysis
- Intravascular lysis
- Phagocytosis by macrophages and neutrophils
What is haemoglobinaemia?
Plasma that contains free Hb
What is haemoglobinuria?
When Hb is found in the urine (in cows this is sometimes called "red fever")
What are some of the causes of haemolytic anaemia?
- Infectious agents e.g. bacteria, parasites
- Oxidative compounds - toxins that damage RBCs
- Fragmentation - mechanical trauma happening to RBCs in circulation
- Immune mediated e.g. blood transfusion reaction, immune system attacks own RBCs
- Inheritied conditions - enzyme deficiencies which means RBCs lyse easily (these are very rare)
Name two types of infectious causes of haemolytic anaemia
- Mycoplasma spp.
Name some examples that cause toxic/oxidative haemolytic anaemia
- Copper posioning
- Red maple
- Snake venoms
What are schistocytes?
Red blood cell fragments
What are spherocytes?
When RBCs look like a small ball as part of the membrane has been removed and it cannot reseal to form a biconcave disk again
What is rouleaux formation?
When RBCs stack together (like coins). This is not normal as RBCs normally have a slight negative charge so they repel each other.