Approach to anaemia (Yr3) Flashcards
what is anaemia?
reduction of the RBC mass
what are the three causes of anaemia?
inadequate production by bone marrow
increased destruction
loss (haemorrhage)
which of the three overall causes of anaemia would be non-regenerative?
inadequate production
which of the three overall causes of anaemia would be regenerative?
increased destruction (some exceptions)
haemorrhage/loss (not regenerative enough)
how do red blood cells typically appear when anaemia is being caused by inadequate production from bone marrow?
normocytic normochromic
how do the red blood cells typically appear in anaemia from increased destruction?
macrocytic hypochromic (lots of reticulocytes)
how do red blood cells usually appear in cases of anaemia caused by haemorrhage?
microcytic hypochromic (lack of iron)
what feature of blood is seen in cases of anaemia caused by haemorrhage?
hypoproteinaemia (whole blood loss)
how do erythrocyte change in response to anaemia?
2,3-DPG increases to lower the haemoglobin affinity for oxygen to improve oxygen delivery to peripheral tissues
what causes the haemic murmur?
changes in the blood viscosity due to anaemia
what is the PCV of a mild anaemia in dogs?
30-36%
what is the PCV of a moderate anaemia in dogs?
18-29%
what is the PCV of a severe anaemia in dogs?
<18%
what is the PCV of a mild anaemia in cats?
20-24%
what is the PCV of a moderate anaemia in cats?
15-19%
what is the PCV of a severe anaemia in cats?
<15%
what are the ways erythrocyte index can be described?
MCV - mean corpuscular volume
MCHC - mean corpuscular haemoglobin concentration
what are findings on haematology of regenerative anaemia?
reticulocytosis
polychromasia
what is reticulocytosis?
increased levels of reticulocytes
how can polychromatophils be visualised?
staining with diff quik
how can reticulocytes be visualised?
stain with new methylene blue
how long does it take for reticulocytes to increase following the onset of anaemia?
2-3 days (all anaemias appear non-regenerative initially)
when do reticulocyte levels peak following onset of anaemia?
4-7 days
what are the two types of feline reticulocytes?
aggregate
punctate
what are the stages of mature red blood cell formation in cats?
nucleated red blood cell
aggregate reticulocytes
punctate reticulocytes
mature red blood cells
how long do feline aggregate reticulocytes last for?
24 hours
how do patients with hypovolaemic shock present?
pallor
tachycardia
weak peripheral pulses
poor peripheral perfusion and cold extremities
what causes hypovolaemic shock?
acute haemorrhage
how is chronic blood loss defined?
bleeding for >2 weeks
what type of anaemia can be caused by chronic blood loss?
iron deficiency anaemia
how long to adult patients have to have chronic haemorrhage for to develop iron deficiency anaemia?
over a month
how is iron deficiency anaemia initially described?
regenerative (will then turn non-regenerative as the iron depletes)
how do red blood cells appear in cases of iron deficiency anaemia appear?
microcytic hypochromic
what is the most common cause of iron deficiency anaemia?
chronic bleeding (typically GI)
what is the usually cause of chronic bleeding resulting in iron deficiency anaemia?
GI - NSAIDs, steroids, neoplasia, ulcers
what can cause chronic bleeding which may result in iron deficiency anaemia?
body system haemorrhage
congenital haemostatic defects
parasitic infestations
(diet is rare but seen in puppies/kittens with vegan diets)
how is iron deficiency anaemia treated?
determine underlying cause
iron supplementation
blood/packed red cell transfusion
what iron supplements are available for iron deficiency anaemia?
oral ferrous sulphate
iron dextran (possible anaphylaxis)
what are the two categories of haemolysis?
immune-mediated
non-immune-mediated
what are some non-immune mediated causes of haemolysis?
oxidative damage (onions, paracetamol, zinc)
intra-erythrocytic parasites
mechanical damage
what is the process of extravascular haemolysis?
antibody binds to RBC
macrophage recognises RBC
RBC undergoes phagocytosis
haem converted to bilirubin
what happens to the ham released from extravascular haemolysis?
converted to bilirubin which is conjugated by the liver and excreted in bile
what are the clinical signs of extravascular haemolysis?
pallor
lethargy
tachycardia, tachypnoea
splenomegaly
jaundice
what happens to free haemoglobin after intravascular haemolysis?
excreted in urine (haemoglobinuria)
processed by liver
what are the two main categories of haemolysis?
intravascular
extravascular
what is a consequence of haemoglobinuria?
renal compromise from tubular epithelial damage (toxic nephrosis )
what are the clinical signs of intravascular haemolysis?
sudden onset (severe)
pallor
collapse
jaundice
tachycardia, tachypnoea
splenomegaly
haemoglobinuria
what are signs of immune mediadiated haemolytic anaemia on haematology?
regenerative anaemia (not always)
autoagglutination
spherocytes
leukocytosis (with left shift)
why might patients with immune mediated haemolytic anaemia present with poorly regenerative anaemia?
acute onset (pre-regeneration)
immune-targeting of RBC precursors
how do spherocytes for?
partially phagocytose RBCs lose their cell membrane which leads to the loss of the discoid shape of the cell (spherocyte)
what does finding spherocytes on haematology strongly suggest?
the animals has IMHA (immune mediated haemolytic anaemia)
where should you look for spherocytes on a blood smear?
around the monolayer
what is autoagglutination?
antibody mediated clumping of red blood cells
what causes autoagglutination?
antierythrocyte IgM
what are rouleaux bodies?
stacking of RBCs due to increased plasma proteins coating RBCs caused by inflammation (cancer)
what animals are rouleaux formations seen as normal?
horses and cats
how can you test if you are seeing a rouleaux or agglutination?
wash anti coagulated blood with saline and the rouleaux will disappear
what is the Coombs test used for?
detect presence of anti-erythrocyte antibodies and complement on RBCs
when can the Coombs test not be used?
if agglutination is already present
what are the two types of immune-mediated haemolytic anaemia?
primary
secondary
what can be some possible triggers for secondary IMHA?
drugs, vaccines, infectious disease, inflammatory disease, neoplasia
what tests could be done if you are suspicious of DIC?
PT or d-dimers
what changes would be seen on biochemistry of animals with IMHA?
elevated ALT and ALP
hyperbilirubinaemia
possible azotaemia
what changes would be seen on urinalysis of an animal with IMHA?
haemoglobinuria
bilirubinuria
proteinuria