Anaemia Flashcards
What is anaemia?
* Decreased red blood cell density- haematocrit/ PCV, RBC, haemoglobin level
What are the clinical signs of anaemia?
Weak/ lethargic/ dull, pale mucous membranes, tachycardic, tachypneic, +/- cool extremities & weak peripheral pulses, +/- heart murmur, +/- icterus, possible shock
What causes Regenerative Anaemia?
Red cell loss from haemorrhage or haemolysis
What causes Non-regenerative anaemia?
Decreased red cell production
With regenerative anaemia, what do you see from the marrow response?
Reticulocytosis, polychromasia, hypochromic macrocytic anaemia
With non-regenerative anaemia, what do you see from the marrow response?
No response. Pre-regenerative or non-regenerative, no reticulocytosis, minimal polychromasia, normocytic normochromic or hypochromic microcytic
What does intravascular haemolysis mean?
Rupture of RBC within the circulation
What does extravascular haemolysis mean?
Phagocytosis of RBC by macrophages in spleen, bone marrow, and liver
What does haemoglobinemia mean?
Excessive haemoglobin in plasma
What does Bilirubinaemia mean?
Excess bilirubin in plasma
What is erythropoietin?
The principle growth factor promoting viability, proliferation and differentiation of erythroid progenitor cells into rubriblasts
Where is EPO produced?
In the kidney in adults and to a lesser extent in the liver in response to hypoxia. In the fetus EPO is produced in the liver
What other growth factors and hormones promote erythropoiesis with EPO?
Stem cell factor, GM-CSF IL-3, TPO and androgens, glucocorticoids, growth hormone, thyroid hormone, insulin, IGF-1
What are the stages of erythropoeisis?
Rubriblast, prorubricyte, rubricyte, metarubricyte, reticulocyte, erythrocyte
What happens in the per-acute stage of regenerative anaemia?
No change Hct or protein
What happens in the acute I phase of regenerative anaemia? How long is this phase?
Within hours. Decreased Hct and protein, fluid shift extravascular to intravascular space, activation of RAAS, no evidence regeneration (pre-regenerative)
What happens in Acute II phase of regenerative anaemia?
Within 5 days. EPO produced–> marrow stimulation, decreased Hct and protein, evidence of regeneration
What will you see with intravascular haemolysis?
Haemoglobinuria, haemoglobinaemia, +/- hyperbilirubinaemia, bilirubinuria, regenerative (unless peracute)
What are some causes of intravascular haemolysis?
Immune mediated disease (IMHA), Infections e.g. Clostridium sp. infection, severe hypophosphatemia, zinc toxicosis, copper toxicosis, oxidative injury (red maple toxicity in horses) genetic disease e.g. PFK deficiency in dogs
What do you see with extravascular haemolysis (within tissues)?
Phagocytosis by macrophages in the spleen, liver, and bone marrow venular sinuses, hyperbilirubinemia, bilirubinuria, regenerative (in most cases), spherocytosis (if immune mediated), schistocytes and keratocytes (if fragmentation)
What are some causes of extravascular haemolysis?
Immune mediated disease, infectious disease e.g. erythrocyte parasites, oxidative damage (intra and extravascular), neoplasia e.g. haemangiosarcoma, fragmentation e.g. DIC, heartworm, drugs e.g. penicillins, genetic disease e.g. hereditary stomacytosis
What will you see with IMHA?
Spherocytosis, auto-agglutination and in saline positive agglutination, Coombs test, exclusion of other primary diseases e.g. neoplasia, infection, or drug therapy
How do we assess for regeneration?
Blood smear (polychromasia) Reticulocytosis Macrocytosis & hypochromasia (large erythrocytes with less haemoglobin, normocytic anaemia does not been it has to be non-regenerative Bone marrow evaluation- erythroid hyperplasia Serial monitoring of PCV/CBC to assess improvement
What are some blood smear changes seen with regenerative anaemia?
Polychromasia, macrocytosis, anisocytosis, hypochromasia (last three only indication in horses), increased Howell-Jolly bodies, increased nucleated RBCs (nRBCs), basophilic stippling
What are the two forms of reticulocytes in cats?
Aggregate reticulocytes= polychromatophils (released in low numbers in normal dogs (1%) and cats (0.4%) and Punctate reticulocytes (more mature form with only a few fine reticulin granules, have a long maturation time in cats (> 2 weeks) so up to 10% punctate reticulocytes are seen in health
What is the best way to assess the degree of regeneration and if it is regenerative?
Absolute reticulocyte count Non regenerative (dog < 80) (cat 500) (cat >200)
What is MCV?
Mean corpuscular volume * average volume of erythrocytes, measured value * Increase- macrocytic, decrease = microcytic
What is MCHC?
Hb per avg. erythrocyte * Increased= not possible. Occurs with haemolysis, lipaemia, heinz bodies * decreased= hypochromic
What is RDW?
Red cell distribution width * measures the variation in cell size * Increased RDW indicates anisocytosis- could reflect macrocytosis and/or microcytosis
What is the equine response to anaemia?
Appears non-regenerative as do not release polychromatophils/ reticulocytes, do not release nucleated RBCs, may have macrocytosis as only indication of regeneration on haemogram/ blood smear
What are the mechanisms of non-regenerative anaemia?
* Reduced erythropoeisis= not making enough erythrocytes * Defective erythropoeisis= making abnormal reticulocytes
What are some causes of reduced erythropoiesis?
Anaemia of inflammatory or chronic disease
Decreased EPO production (renal disease)
Marrow disease
Immune mediated (pure red cell aplasia)
Infections
Iron deficiency
B12 or folate deficiency
Lead poisoning
Marrow disease
Genetic disease e.g. macrocytosis of poodles
What are the mechanisms of anaemia of inflammatory disease?
Iron sequestration (hepcidin mediated), decreased erythrocyte survival, impaired production
What are laboratory findings of anaemia of inflammatory disease?
normocytic, normochromic, mild to moderate anaemia that is fairly stable, decreased serum iron
What are some causes of decreased EPO production?
Chronic renal disease- mild to moderate anaemia is due to decreased EPO production, reduced RBC lifespan, GIT bleeding and uraemia suppression of erythropoeisis and Endocrine disease- hypoadrenocorticism, hypoandrogenism, hypopituitarism (mechanisms not understood)
What is myelophthisis?
Infiltration of marrow by neoplastic cells e.g. lymphoma
Causes non-regenerative anaemia (bone marrow is sick)
What is myelofibrosis?
Fibrosis of the marrow
Causes non-regenerative anaemia (bone marrow is sick)