Haematology (Yr 3) Flashcards
what is anaemia?
reduction of RBC mass below the reference values for PCV, RBC count or total Hb
what are the three pathophysiological causes of anaemia?
inadequate production by bone marrow
increased destruction
loss (haemorrhage)
what type of anaemia is usually seen with inadequate production by bone marrow?
non-regenerative
normocytic normochromic
what type of anaemia is usually seen with increased destruction of RBCs?
regenerative
microcytic hypochromic
what type of anaemia is usually seen due to haemorrhage?
not regenerative enough
microcytic hypochromic
(hypoprotainaemia also seen)
how does the body respond to anaemia?
2,3-DPG increases in erythrocytes to give a lower oxygen-Hb affinity to allow better delivery to peripheral tissues
altering tissue perfusion
erythropoietin stimulates erythropoiesis
alterations to behaviour
what are some clinical signs seen with anaemia?
pallor
weakness
exercise intolerance
tachycardia/tachypnoea
haemic murmur
what are some possible findings on clinical examination of an animal with anaemia?
pallor
weakness
tachycardia/tachypnoea/dyspnoea
haemic murmur
icterus
petechiation
evidence of bleeding
pyrexia
lymphadenopathy
abdominal pain/mass or splenomegaly
what are the ways anaemia can be classified?
severity (mild/moderate/severe)
erythrocyte index (MCV, MCHC)
regenerative response
what is mild anaemia in dogs and cats?
30-36% dogs
20-24% cats
what is moderate anaemia in cats and dogs?
18-29% dogs
15-19% cats
what is severe anaemia in cats and dogs?
<18% dogs
<15% cats
what is MCV?
mean corpuscular volume (size of RBC)
what is MCHC?
mean corpuscular haemoglobin concentration (colour of RBC)
how can MCV of an RBC be described?
microcytic
normocytic
macrocytic
how can MCHC of an RBC be described?
hypochromic
normochromic
how are polychromatophils stained?
diff quik
how are reticulocytes stained?
new methylene blue
what are two classic signs on haematology of regenerative anaemia?
reticulocytosis
polychromasia
why do anaemias appear non-regenerative initially?
it takes 2-3 days for the reticulocyte count to increase
is the percentage reticulocyte count of absolute reticulocyte count more accurate?
absolute
what are the main causes of regenerative anaemia?
haemolysis
haemorrhage
what are the two types of immature reticulocyte?
aggregate (24 hours)
punctate (up to 10 days)
what causes hypovolaemic shock?
acute haemorrhage of all blood components
why will PCV and TP continue to fall even after acute haemorrhage has been stopped?
interstitial fluid moves into the vascular space so replace the lost blood volume, diluting the proteins nd RBCs
what is chronic blood loss?
continuous bleeding for >2 weeks
what type of anaemia can develop in cases of chronic blood loss?
iron deficiency anaemia
how regenerative is anaemia causes by chronic bleeding and iron deficiency?
initially is regenerative, will because less and less as the iron stones are used up
what is the appearance of RBCs in cases of iron deficiency anaemia?
microcytic hypochromic
what are some possible causes of iron deficiency anaemia?
chronic GI bleeding (most common) - NSAIDs, ulcers, neoplasia
parasite infections
congenital haemostatic defects
dietary is rare
how is iron deficiency anaemia treated?
treat underlying cause
iron supplementation (oral ferrous sulphate)
blood transfusion
why should you be cautious when using iron dextrans IM injection to treat iron deficiency anaemia?
can cause anaphylaxis
(is also painful)
what are the two main 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 (angiopathic anaemia)
what happens during extravascular haemolysis?
antibody binds to RBC
macrophages recognise RBC
phagocytosis/lysis of RBC
haem converted to bilirubin
bilirubin is conjugated in the liver
how do spherocytes form?
from partial phagocytosis of RBCs
what happens is the livers capacity for conjugating bilirubin is overwhelmed?
hyperbilirubinaemia leading to bilrubinuria and jaundice
what happens during intravascular haemolysis of RBCs?
intravascular cell lysis
complement is activated\
haemoglobinaemia leading to haemoglobinuria and renal compromise
why does intravascular haemolysis cause renal compromise?
the free haemoglobin leads to damage to tubular epithelium
what are the possible clinical signs of intravascular haemolysis?
severe illness/sudden onset
pallor
collapse
jaundice
tachycardia/tachypnoea
splenomegaly
haemoglobinuria
what are the signs on haematology of immune mediated haemolytic anaemia?
usually regenerative
autoagglutination
spherocytes
leukocytosis with left shift
what test can be used to diagnose IMHA?
Coombs
what is the Coombs test?
confirms the presence of anti-RBC antibodies by causing agglutination of the RBCs if they have anti-RBC antibodies on them
how do macrophages cause spherocytes to form?
partial phagocytosis leads to decreased RBC surface forming a discoid shape
where should spherocytes be looked for on a smear?
in the monolayer (this is where you should look at RBC morphology)
what could cause autoagglutination of RBCs?
antierythrocyte IgM (or very high IgG)
what is the difference between agglutination and rouleaux formation?
agglutination is antibody mediated clumping that is strongly supportive of IMHA
rouleaux formation is stacking of RBCs due to increased plasma proteins coating RBCs, caused by inflammation or cancer (normal in cats)
how can you determine if a structure is a rouleaux formation or autoagglutination?
add saline to a drop of anti coagulated blood, the rouleaux formations will disappear
what changes will be seen on biochemistry in IMHA cases?
elevated ALT and ALP
hyperbilirubinaemia
possible azotaemia
what changes will be seen on urinalysis of IMHA cases?
haemolgobinuria
bilirubinuria
proteinuria
what needs to be done before starting treatment for IMHA?
complete all diagnostic tests (immunosuppressants can mask underlying causes)
what does IMHA treatment involve?
immuno-suppressive therapy
antithrombotic therapy
supportive therapy
what would be the first choice drug for immunosuppressive therapy in IMHA?
prednisolone
what are some side effects of corticosteroids?
PU/PD, polyphagia
muscle wastage
GI signs - gastritis, ulceration
when would you consider using a second immunosuppressant in IMHA cases?
if clinical features of life threatening disease
no response to corticosteroids over first 7 days
if patient is at risk of severe side effects
what is a salvage therapy for IMHA if immunosuppressants don’t work?
immunoglobulins (human IVIG) that block macrophage receptors
how long are IMHA animals typically on immunosuppressants?
4-8 months
what can be used as antithrombotic therapy for IMHA cases?
antiplatlet drugs - clopidogrel
anticoagulants - heparin
what are some supportive therapies used for IMHA treatment?
blood transfusion
gastroprotectants (omeprazole) if evidence of GI bleeding/ulcers
what is neonatal isoerythrolysis?
destruction of neonates RBCs by maternal antibodies from colostrum
what is microangiopathic haemolytic anaemia?
RBCs get mechanically damage as they pass through fibrin meshwork in the microvasculature, these damaged cells are then removed rapidly from circulation
what are some possible causes of microangiopathic anaemia?
altered vasculature (haemangiosarcoma…)
fibrin nets (DIC)
glomerulonephritis
congenital cardiac defects
what are schistocytes?
fragmented RBCs
what are some possible causes of acanthocytes?
liver disease (hepatic lipidosis)
splenic haemangiosarcoma
lymphoma
high cholesterol diets
what can cause oxidative injury to RBC?
paracetamol - cats
onions, zinc - dogs
why does oxidative injury to RBCs cause anaemia?
RBCs become more fragile so undergo haemolysis or are phagocytosed more readily
what cell morphology is seen with oxidative damage to RBCs?
heinz bodies
what are Heinz bodies?
round pale inclusions on the inner surface of RBC membrane due to denatured haemoglobin
what animals is it normal to see some Heinz bodies in?
cats
what is used to treat paracetamol poisoning in cats?
N-acetyl cysteine
what type of anaemia is seen with Mycoplasma haemofelis?
regenerative
how is Mycoplasma haemofelis treated?
doxycycline and prednisolone
(cats will remain carriers)
what can cause a non-regenerative anaemia?
primary/secondary marrow disease
lack of erythropoietin (kidney disease)
