Haematopoetics Flashcards
why is anaemia common in cats?
cats mask illness and disease so are diagnosed later
lifespan of cat RBC is shorter than that of a dog
total RBC mass lower in cats than dogs
feline haemoglobin has low affinity for O2
what is the effect of the shortened lifespan of feline RBC?
anaemia is a clinical issue more quickly as functional RBC are lost quicker
what does it mean if RBC have low affinity for oxygen?
O2 is given up to tissues easily
what is the effect of low feline haemoglobin affinity for oxygen?
anaemia better tolerated
what are the clinical signs of anaemia?
pale MM
less commonly: yellow MM
lethargic
weak
hyperdynamic pulses
tachycardia
heart murmur
tachypnoea
enlarged LN and spleen
pica
why is heart murmur seen with anaemia?
altered viscosity of blood changes the flow of blood through the heart
what is the murmur seen with anaemia known as?
haemic murmur
when is an enlarged spleen seen with anaemia?
when it is linked to RBC breakdown and removal
what is the first investigation used for anaemia?
haematology (PCV)
blood smear
what effect does acute haemorrhage have on blood and RBC volume?
PCV will appear normal as volume has been lost
are animals anaemic following acute haemorrhage?
yes - reduced O2 carrying capacity
what is seen on PCV with chronic anaemia?
reduced proportion of RBC to plasma
PCV low
what is seen on PCV with volume overload?
normal RBC volume but increased blood volume so PCV appears low
what is the fundamental issue seen with anaemia?
not enough RBC
what are the 2 types of anaemia?
regenerative
non regenerative
what are the signs seen on blood smear of regenerative anaemia?
reticulocytes >50x10^9/L
anisocytosis
polychromasia
MCV increased
MCHC increased
what are the signs of non-regenerative anaemia seen on blood smear?
reticulocytes <50x10^9/L
normocytic
normochromatic
MCV normal
MCHC normal
what number of reticulocytes are seen with regenerative anaemia?
> 50x10^9/L
what number of reticulocytes are seen with non-regenerative anaemia?
<50x10^9/L
what are reticulocytes?
immature RBC sent into circulation to make up for RBC deficit
what is anisocytosis?
variation in cell size
what is polychromasia?
variation in RBC color density
why is MCV increased with regenerative anaemia?
RBC are larger as immature and sent from the bone marrow before they have shrunk
why is MCHC decreased in regenerative anaemia?
cells are less concentrated when they are reticulocytes
why are the signs of non-regenerative anaemia seen?
bone marrow is not responding to anaemia by producing immature cells so morphology is normal
define hypochromic
pale due to reduced haemoglobin
what are normocytic RBC?
normal size RBC
what are microcytic RBC?
small RBC
what are macrocytic RBC?
large RBC
what reticulocytes may be seen in normal cats?
punctate reticulocytes
what are punctate reticulocytes?
immature RBC that may be released slightly early from bone marrow in cats
why may punctate reticulocytes be seen in cats?
RBC take longer to mature in cats so may be released slightly early
what type of reticulocytes are seen in cats undergoing active regeneration?
aggregate
what stain must be used for reticulocytes to be viewed on blood smear?
new methylene blue stain only
what is the best way to establish whether anaemia is regenerative?
complete an absolute reticulocyte count
what is the formula used to calculate absolute reticulocyte count?
absolute reticulocyte count (x10^9/L) =
observed % reticulocytes x automated RBC count (10^12/L)
where should the total RBC count be taken from?
haematology machine
what are the factors which make it harder to categorise anaemia?
duration
concurrent disease
why does duration of anaemia make it hard to differentiate between regenerative and non-regenerative?
in the first few days reticulocytes may not be released from bone marrow and so anaemia may not appear regenerative even of it is
how can concurrent disease affect differentiation between regenerative and non-regenerative anaemia?
may suppress bone marrow response and make anaemia appear non-regenerative when it is not
what concurrent disease may suppress the immune system?
leukaemia
infections
inflammation
why may chronic anaemia become non-regenerative?
iron deficiency makes it impossible for the body to respond to anaemia and so becomes non-regenerative
what are the 2 reasons for regenerative anaemia?
haemorrhage
haemolysis
what are some of the reasons that haemorrhage may cause regenerative anaemia?
trauma
coagulopathies
chronic blood loss from flea infestations
chronic blood loss from infected tumors
chronic GI losses
what are the main causes of regenerative anaemia due to haemolysis?
infectious
immune mediated
heinz body anaemia
severe hypophosphataemia
incompatible blood transfusions
neonatal isoerythrolysis
inherited defects
what are the main infectious causes of regenerative anaemia due to haemolysis?
FeLV
FIA
what are the main immune mediated causes of regenerative anaemia due to haemolysis?
drugs
neoplasias
FeLV
what can cause Heinz body anaemia?
paracetamol or onion toxicity
lymphoma
when is severe hypophosphataemia seen?
refeeding syndrome
what is feline infectious anaemia caused by?
mycoplasma haemofelis
how is mycoplasma haemofelis transmitted?
fleas
how is mycoplasma haemofelis diagnosed?
PCR
what can be the signs of mycoplasma haemofelis?
pyrexia
jaundice
what is essential if animals are tableted doxycycline?
followed with syringed water or food
how is mycoplasma haemofelis treated?
doxycycline
what is the risk associated with doxycycline?
oesophagitis
oesophageal stricture
what type of anaemia do most cats have?
non-regenerative
what can be used for diagnosis when anaemia is severe?
bone marrow sampling
what does non-regenerative anaemia often occur secondary to?
systemic disease e.g. FIP/FIV/bacterial infection
how does chronic inflammation lead to mild non-regenerative anaemia?
bone marrow suppression
sequestrum of iron
how may anaemia be treated?
blood transfusions
erythropoietin
bone marrow stimulation
why may cats be critical on presentation of anaemia?
compensation due to low haemoglobin affinity for O2
what is blood transfusion a useful treatment for?
adjunct treatment for FIA
non-regenerative anaemias
what may erythropoietin be used for?
treatment of anaemia in cats with CKD
what erythropoietin treatments are available?
recombinant human treatments
have lower side effects
when may bone marrow stimulation be used to treat anaemia?
when underlying cause of bone marrow failure is unknown
how does bone marrow stimulation treat anaemia?
low evidence base
thought to manage immune-mediated mechanism that has been proposed in some cases of BM failure
what is a bleeding disorder?
abnormal condition which allows blood to escape from injured blood vessels or interferes with haemostasis following injury
in what species are bleeding disorders more common?
dogs
what are the 2 mechanisms for haemostasis?
primary
secondary
what is the aim of primary haemostasis?
constriction to reduce blood flow
platelet plug forms
when do primary and secondary haemostasis occur?
simultaneously in reality
what occurs within a blood vessel when it is injured?
leakage of blood from the vessel resulting in bruising or visible bleeding
endothelium of BV secretes activating factor
vessel constricts
what is the role of the activating factor secreted by blood vessels following injury?
attracts platelets
how do platelets form the platelet plug within the vessel deficit?
swell and stick together
what is DIC?
disseminated intravascular coagulation
what causes DIC?
inappropriate activation of clotting factors
clotting factors eventually exhausted so patient begins bleeding
what is the role of Von willebrands factor in haemostasis?
increases platelets stickyness
maintains formed platelet plug
helps stop the clot from breaking off
what is the role of the primary haemostatic platelet plug?
plug hole to allow body to repair the defect without continual bleeding
what is needed for vessels to fully repair?
secondary haemostasis
what occurs in Von Willebrands disease?
deficiency of vWF in endothelial layers of blood vessels
either non produced or not enough
what is the commonest inherited haemostatic disorder in dogs?
von Willebrands disease