Approach to anaemia 1 Flashcards
What is anaemia defined as?
Reduction of either:
- PCV or haematocrit
- RBC count
- Haemoglobin
Is anaemia associated with underlying disease?
Always - anaemia is a clinical sign, not a disease
Is acute or chronic anaemia worse?
Acute
Chronically anaemic animals can compensate
What are examples of responses to anaemia?
Increased RBC 2,3 DPG
Alterations in tissue perfusion
Alterations in behaviour
Different oxygen affinity behaviour (cats only)
What does 2,3 DPG do?
Lowers affinity of haemoglobin for oxygen
Facilitates release of oxygen
How does increased RBC 2,3 DPG help in response to anaemia?
Increased RBC 2,3 DPG causes lower O2-haemaglobin affinity
Better delivery of oxygen to tissues
What can only cats do in response to anaemia?
Different haemoglobins - respond over range of oxygena conditions
Tissue perfusion alters in response to anaemia. What hormonal effect does this have?
Lack of perfusion causes increased erythropoietin
Where is erythropoietin produced? What does it do?
Kidneys
Stimulates RBC production
Give an example of a behaviour associated with anaemia, particularly in cats
Pica
Give examples of what you may see on a physical exam of an anaemic animal
Jaundice Pallor Weakness Prolonged CRT Tachycardia etc
How can anaemia be classified (3 descriptions)
Degree of severity
Erythrocyte indexes
Regenerative response
What are the 3 degrees of severity for anaemia?
Mild, moderate, severe
What are examples of erythrocytes indexes when describing anaemia?
Microcytic, normocytic or microcytic
Hypochromic or normochroic
What are the 3 main causes of anaemia?
Inadequate production by bone marrow
Increased destruction of RBCs
Haemorrhage
What types of anaemia can be caused by inadequate production by bone marrow - severity, RBC index and regeneration?
Mild to severe
Normocytic, normochromic
Non-regenerative
What type of anaemia can be caused by increased destruction of RBCs - regeneration, RBC index and immune mediated?
Regenerative
Macrocytic hypo chromic or normocytic normochromic
Immune mediated or non-immune mediated
Does haemorrhage cause proportional or disproportional loss of blood components? Does it cause regenerative or non-regenerative anaemia?
Proportional
Regenerative usually
How does the body recover hypovolaemia after haemorrhage?
Interstitial fluid moves into vascular space (within a few hours)
A few hours after haemorrhage, how does the total protein differ? What other haematological abnormalities are present?
Low total protein - blood diluted by ISF
Decreased PCV, haematocrit and erythrocyte mass
How can acute blood loss present clinically?
Hypovolaemic shock - pallor, tachycardia, weak pulse, cold extremities, increased lactate
How long does blood need to be lost to define it as chronic?
More than 2 weeks
How long does chronic blood loss need to continue to develop iron deficiency anaemia in an adult?
1 month - abundant iron supply
Does acute or chronic blood loss cause IDA?
Chronic
Is chronic blood loss regenerative or non-regenerative?
Can be either
Eventually lack of iron slows down erythropoiesis
What 2 things on a blood smear indicates regenerative anaemia?
Reticulocytosis
Polychromasia
What stain is used for reticulocytes?
Methylene bue
Is reticuocytosis or polychromasia more accurate to diagnose regenerative anaemia?
Reticulocytosis
Rely on absolute count not % - do manually as can be mistaken as WBC
When do reticulocytes become present from the onset of regenerative anaemia? When are they at peak levels?
Start 2-3 days after onset
Peak at 4-7 days
What can cause iron deficiency anaemia?
Chronic haemorrhage
Dietary deficiency
Congenital haemostatic defects
Parasitic infestations
What is the most common cause of iron deficiency anaemia? What can cause this?
GI haemorrhage
NSAIDs, ulceration, neoplasia, parasites
How does iron deficiency affect red blood cells size and colour?
Causes hypochromic and microcytic RBCs
How does iron deficiency cause microcytic and hypo chromic RBCs?
Production of haemoglobin defective with iron deficiency
Extra divisions of RBC precursors cause smaller and hypo chromic RBCs
Give examples of drugs that can be used to treat chronic GI haemorrhage
Sucralfate
Ranitidine
Omeprazole
Why should antacids be administered several hours apart from each other?
Interfere with iron absorption
How is IDA treated?
Treat underlying cause
Iron supplementation
(RBC transfusion)
What can be given for iron supplementation with IDA?
Oral ferrous sulphate
Intramuscular iron dextran
Why should precautions be taken when administering iron dextran IM?
Painful
Can cause anaphylaxis
Can IDA be caused by a dietary deficiency?
Yes - if vegan diet
Particularly puppies and kittens
Supplement and transfer diet
What are the 2 causes of immune mediated RBC destruction?
Immune mediated haemolytic anaemia
Neonatal isoerythrolysis
Briefly describe the pathogenesis of IMHA?
Production of antibodies against RBCs
RBCs removed by macrophages
In which organs does extravascular haemolysis take place?
Spleen
Liver
Bone marrow
Extravascular haemolysis causes the release of what products?
Unconugated bilirubin
Aminoacids
Globin
Iron
What affect does extravascular haemolysis have on the spleen and liver?
Enlargement - splenomegaly and hepatomegaly
What are the symptoms of extravascular haemolysis?
If liver capacity overwhelmed - hyperbilirubinaemia, bilirbuinurea, jaundice
Collapse etc
What colour is urine depending on if haemolysis is intra or extravascular?
Intravascular = red urine Extravascular = yellow urine
What are the symptoms of intravascular haemolysis?
Haemoglobinaemia
Haemoglobinuria
How can intravascular haemolysis cause renal compromise?
Free haemoglobin damages tubular epithelium
What on a blood smear is strongly supportive of IMHA?
Spherocytes
Look smaller but actually just spherical shape
How can spherocytes be differentiated from microcytes?
Microcytes have central pallor, spherocytes do not
How does IMHA cause spherocytes?
Macrophages pit membrane of RBC
Decreased RBC surface causes loss of shape
Is IMHA primary or secondary to infection or neoplasia?
Either
Where on a blood smear should you look for spherocytes?
Monocyte layer
How can immune mediated haemolytic anaemia be diagnosed by blood smear?
Regenerative anaemia WITH
Marked spherocytosis and or agglutination
Why does IMHA cause auto agglutination?
Antierythrocyte antibodies high - causes agglutination
Can be macro (visible grossly) or micro
IMHA can lead to cell lysis or cell ghosts - how?
RBC directly damaged by complement
Why shouldn’t immunosuppressive drugs be given without finding cause of IMHA?
May be due to infection, cause animal to get sicker
How can IMHA be diagnosed?
Clinical signs
Haematology
Coomb’s test
What is Coombs’ test used for? When might it not work?
For autoimmune haemolyticc anaemia - detects anti RBC antibodies
Cannot be done if agglutination already present
What is the Alvedia anti globulin test used for?
IMHA
Immunochromatography done in house
What can cause non-immune mediated increased destruction?
Oxidative damage
Intraerthrocytic parasites
Mechanical damage - angiopathic anaemia
Bacteria/viruses
What can cause oxidative damage?
Onion, garlic
Red maple (horses)
Paracetamol (cats)
Copper (sheep)
Give 2 examples of intra-erythrocytic parasites
Babes
Mycoplasma haemofelis
