Approach to anaemia 1 Flashcards
Define anaemia
A deficiency in the number or quality of red blood cells in your body
Anaemia is a value below the reference interval of which tests?
- PCV
- RBC count
- Total Hb
Anaemia is associated with which clinical sign?
Pallor - mucous membrane colour is paler than normal
Anaemia is always associated with?
An underlying disease
- anaemia is a clinical sign, not a disease
What are the 3 causes of anaemia?
- inadequate production of RBCs by the bone marrow (non-regenerative)
- Increased destruction of RBCs (regenerative)
- Loss: haemorrhage (not regenerative enough)
How do cells look in non-regenerative anaemia?
Normocytic
Normochromic
- cells look normal, just smaller in number
How do cells look in regenerative anaemia?
Macrocytic
Hypochromic
(big RBCs that are blue in colour)
How would cells look in anaemia that is not regenerative enough e.g. haemorrhage?
Microcytic
Hypochromic
- small pale red cells
Would also see hypoproteinaemia
In response to anaemia, the levels of what substance increase in erythrocytes?
2-3 diphosphoglycerate (2-3 DPG)
What is the role of 2-3 diphosphoglycerate (2-3 DPG)?
Lowers oxygen haemoglobin affinity which increases oxygen delivery to peripheral tissues
Name the hormone that drives erythropoiesis?
Erythropoietin
How do the levels of erythropoietin change in response to anaemia, and what is the effect of this change?
- levels increase
- stimulates bone marrow to increase erythropoiesis
How does behaviour change in response to anaemia?
Behaviour changes to reduce oxygen requirements
Give examples of clinical signs of anaemia
- pallor
- weakness
- exercise intolerance
- tachycardia
- tachypnoea
How would you approach gathering the history of an anaemic animal?
- acute or chronic onset of signs
- weakness, lethargy
- evidence of external blood loss
- access to toxins
- recent drug therapy
- is urine normal
What count is required in the full haematology test?
Reticulocyte
Which tests would be undertaken in a suspected anaemic animal?
- full haematology
- total protein, albumin, globulin
- biochemistry
- urinalysis
- diagnostic imaging
- saline agglutination
What is the purpose of a saline agglutination test?
It is used to determine whether red cell agglutinates are present in a blood sample.
When red cell agglutinates are present this indicates that anaemia is due immune-mediated haemolysis.
Which 3 factors classify anaemia?
- degree of severity based on PCT/Hct
- erythrocyte index
- regenerative response
PCVs under what value indicate severe anaemia in:
- dogs
- cats
- less than 18%
2. less than 15%
Which stain shows erythrocytes?
New Methylene blue
What are the hallmarks of regeneration?
Reticulocytes = large, blue staining cells
Polychromasia
Define polychromasia
Polychromasia is the presentation of multicolored red blood cells in a blood smear test. It’s an indication of red blood cells being released prematurely from bone marrow during formation
How many days within the onset of anaemia does it take for reticulocyte numbers to increase?
2-3 (anaemia will initially appear non-regenerative)
- numbers peak at 4-7 days
What are the 2 main causes of regenerative anaemias?
- haemorrhage
- haemolysis
Describe the 2 forms of feline reticulocytes
Aggregate - last 24 hours
followed by…
Punctate - last up to 10 days
How can you tell apart aggregate and punctate feline reticulocytes?
Aggregate stain a lot more purple/blue than punctate
Reticulocyte count in cats should be based on the … count
Aggregate
Hypovolaemic shock occurs as a result of?
Acute haemorrhage
How does hypovolemic shock present?
- Pallor
- Tachycardia, Weak peripheral pulses
- Poor peripheral perfusion, cold extremities
How will acute haemorrhage affect PCV:
- immediately
- after 24 hours
- initially PCV will be normal as there has been a proportional loss of all blood components
- after 24 hours PCV will decreased as interstitial fluid moved into circulation
Chronic blood loss is defined as bleeding for?
more than 2 weeks
Chronic blood loss leads to which classification of anaemia?
Iron deficiency anaemia due to consumption of iron stores
- takes over one month of blood loss to occur
What are the classical changes in red cell morphology in iron deficiency anaemia?
Microcytic
Hypochromic
- smaller and paler in colour
Describe the process of iron deficiency anaemia resulting in smaller, paler cells
- during erythrocyte formation there needs to be enough Hb to trigger spitting out a nucleus
- when there is not enough iron to make Hb there is an extra division of precursor cells to try and increase time for Hb accumulation
What can cause chronic bleeding of the GI tract?
NSAIDs
Steroids
Neoplasia
Ulcers
What is a polychromatophil?
An immature red blood cell which has already lost its nucleus.
An elevated number of polychromatophils suggests an increased production of erythrocytes by the bone marrow
How can iron deficiency anaemia be treated?
Iron supplementation - oral ferrous sulphate
Increased destruction of RBCs is called?
Haemolysis
What is immune mediated haemolytic anaemia?
- most common cause of haemolysis
- Production of antibodies against patients red blood cells, which are then removed by macrophages
What are some causes of non-immune mediated haemolytic anaemia?
- Oxidative damage: onions, paracetamol in cats, zinc,
- Intra-erythrocytic parasites
- Mechanical damage (angiopathic anaemia)
Describe extravascular haemolysis
- antibodies bind to RBC
- macrophages recognise RBC
- phagocytosis and lysis occurs
What arises from partial phagocytosis of red blood cells?
Spherocytes
Haem in RBCs is converted to … following extravascular haemolysis?
Bilirubin
What are the consequences of increased bilirubin levels following haemolysis?
- conjugated by the liver and excreted with bile
- if the liver is overwhelmed => hyperbilirubinaemia => jaundice
Describe intravascular haemolysis
- intravascular cell lysis
- extensive complement activation
- haemoglobinaemia
- haemoglobinuria
What are the consequences of haemoglobinuria following intravascular haemolysis?
Renal compromise
- tubular epithelial damage
How can immune mediated haemolytic anaemia be diagnosed?
- Clinical signs
- Typically regenerative, agglutination, spherocytes, leukocytosis with left shift
- direct antiglobulin test (Coombs test)
Describe the appearance of spherocytes
Small, round, dense
- no area of central pallor
The presence of many spherocytes is indicative of which type of anaemia?
Immune mediated haemolytic
What do RBC ghosts show?
That a cell has been lysed
- not specific for IMHA
What is agglutination strongly indicative of?
Immune mediated haemolytic anaemia
What is rouleaux formation?
Stacking of RBCs due to increased plasma proteins coating RBCs
What are the causes of rouleaux formation?
Inflammation
Cancer
In which species is rouleaux formation seen normally?
Horses
Cats
How can the saline agglutination test be used to differentiate an agglutination from a rouleaux?
1 drop of anticoagulated blood + 4 drops of saline
- Rouleaux will dissapear
- Agglutination persists
Give examples of possible triggers of secondary immune mediated haemolytic anaemia
- drugs
- infectious disease
- inflammatory disease
- neoplasia
- vaccines
