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
what breeds is vWF disease seen in?
dobermanns
what is the effect of vWF disease?
platelet adhesion and clumping impaired
what is the result of secondary haemostasis?
fibrin formation
what is fibrin?
protein scaffold which supports platelet plug
what is the role of fibrin?
stabilises primary haemostatic platelet plug in big wounds / vessels
what are the pathways involved in making fibrin?
intrinsic
extrinsic
common
what is the difference between the intrinsic and extrinsic pathways for secondary haemostasis?
different clotting factors involved in each process
what is the role of the intrinsic pathway of secondary haemostasis?
initiation of secondary haemostasis
what is the role of the extrinsic pathway in secondary haemostasis?
amplification of clotting/secondary haemostasis
what does fibrin result from?
activation of the clotting cascade
what happens during the activation of platelets in primary haemostasis?
receptors on the inside of the platelets are flipped onto the surface and make the platelets stickier
why is it important that primary haemostasis is local?
so that blood in the area still flows and doesn’t all clot
why can Von Willebrand’s disease cause inadequate or no vWF production?
gene has incomplete penetrance
effect may be partially seen
what are clotting factors?
enzymes which catalyze a cascade of reactions that breakdown proteins to make fibrin from fibrinogen
what is the role of clotting factors produced by the clotting cascade?
conversion of prothrombin to thrombin
what is the role of thrombin?
catalyses conversion of fibrinogen to fibrin
what organ is heavily involved in clotting?
liver
what is the role of the liver in haemostasis?
all clotting factors made in the liver
what can be the impact of liver disease on haemostasis?
coagulopathies as clotting factors not produced properly
what vitamin is a key part of secondary haemostasis?
vitamin K
how is vitamin K involved in secondary haemostasis?
enzymes use vitamin k when working to create clotting factors and when regenerating
why does rodenticide toxicity lead to coagulopathy?
rodenticide causes reduction in vitamin K dependent factors as it is bound and removed by the poison meaning no new clotting factors can be created
how else may patients become vitamin K deficient and so develop clotting disorders?
if not eating
issues with fat digestion
why does inappetance lead to vitamin K deficiency?
it is a fat soluble vitamin so if not eating clotting disorders will follow
why may patients have an issue with fat digestion?
blocked bile ducts (stones or pancreatitis)
what is affected by defects in primary haemostasis?
platelets
vessels
how can platelets be affected in primary haemostasis defects?
reduced number (thrombocytopenia)
reduced function
how can vessels be affected in primary haemostasis defects?
vasculitis
what is vasculitis?
vessels unable to vasoconstrict and leaky
what is affected in defects of secondary haemostasis?
clotting factors
what are the main secondary haemostasis defects?
quantitative disorders
qualitative disorders
what are quantitative secondary haemostasis disorders caused by?
reduction in number of clotting factors
what are qualitative secondary haemostasis disorders caused by?
reduction in function of clotting factors
how is reduction in function of clotting factors caused?
genetic - issue with protein itself
what are the 3 areas of the clinical approach to a bleeding patient?
history
clinical signs
lab investigation
what arm of the clotting cascade is affected by vitamin K deficiency?
extrinsic arm
when do animals usually present with inherited bleeding disorders?
< 6 months of age
how may breed indicate what bleeding disorder is present?
e.g. dobermann and vW disease
why may gender help to identify bleeding disorder?
haemophilia is X linked and affects males only
what in a patients history can assist in identification of bleeding disorders?
response to previous trauma
any toxin ingestion
drug use
previous bleeding
any relatives with bleeding signs
what are primary haemostatic disorders typically characterised by?
multiple minor bleeds
prolonged bleeding
why do primary haemostatic disorders lead to prolonged bleeding?
platelet plug weak so is regularly knocked off as blood flows past
what are secondary haemostatic disorders typically characterised by?
single large bleeds
rebleeding from injury site
what are typical signs of primary haemostatic diseases?
petechiae
ecchymosis
multiple bleeding sites
surface bleeding
prolonged bleeding from venepuncture / cuts
unexpected bruising
what are typical signs of secondary haemostatic diseases?
haematomas
delayed bleeding or rebleeding from a cut
deep and cavity bleeds
venepuncture usually fine
localised site of bleeding
when should samples be collected for blood disorder testing?
before any treatment starts
what tube may be used to check clotting?
sodium citrate
what is crucial when using sodium citrate tubes?
must be filled exactly otherwise reversal agent used in the lab won’t work
what are sodium citrate tubes used for?
stopping clotting until at the lab where the process can be reversed and clotting restarted
how should samples be handled?
may need to go in the fridge
check with lab if posting
what tube should be filled first?
biochem
why should biochem be filled before EDTA?
anticoagulant in EDTA can affect Ca2+ reading if syringe touches side
what tests can be used for primary haemostasis testing?
platelet count
buccal mucosal bleeding time
vWF testing
why is atraumatic venepunture vital for bleeding disorder patients?
avoid excessive activation of haemostasis and local consumption of platelets
what is BMBT a test for?
platelet defects (both platelet number and function) and vessel wall defects.
if thrombocytopenia is identified is BMBT needed?
no - as BMBT will be prolonged
what may increase BMBT?
thrombocytopenia
vWF disease - impaired platelet function
DIC
what is seen on BMBT of animals with coagulation defects?
normal but rebleeding seen
what is normal BMBT in dogs?
<3.5 mins
what is normal BMBT in cats?
<3.5 mins
what animals should BMBT be performed on?
conscious dogs
sedated or GA cats
how is BMBT performed?
The patient is placed in lateral recumbency and the upper lip folded up and held in place with a gauze bandage
A pair of small standardised incisions are made in the buccal mucosa with the cutting device in the kit
Blood is blotted away using filter paper, without disturbing the incision sites. The time taken for cessation of bleeding is recorded.
how is platelet count estimated?
good quality blood smear
what are platelet counts used for?
identification of quantitative platelet disorders
what stain is needed for platelet counts?
diff-quick
how is a platelet count performed?
Under low power the smear is scanned for any platelet clumps which would influence the count obtained and, under oil immersion (x 100), the number of platelets per high power field are counted. This is repeated for around ten fields so that an average platelet count per high power field is obtained.
what does each platelet per high power field represent?
~20x10^9/L platelets in circulation
what is the normal platelet count?
200-500 x 10^9/L
what number of platelets on platelet count would suggest bleeding likely?
<50 x 10^9/L
how many platelets per HPF are considered normal?
11-25
what part of secondary haemostasis is tested via activated clotting time (ACT)?
intrinsic and common pathway
what is found in activated clotting time tubes?
diatomaceous earth which activates the intrinsic pathway
what must be done before blood is placed in tube to test ACT?
First few drops of blood sampled are discarded in case of endothelial activation factorsinterfering with the test results
why must the first few drops of blood be discarded before ACT testing is performed?
in case of endothelial activation factorsinterfering with the test results
how is activated clotting time tested?
2 mls blood is collected into the test tube. The test tube is gently inverted to mix and then left undisturbed for 40 seconds. The tube is then inverted every 10 seconds and the time taken for complete clot formation recorded.
what pathways are tested by activated partial thromboplastin time?
intrinsic
common
what tube is needed to test activated partial thromboplastin time?
sodium citrate
what is the benefit of activated partial thromboplastin time over activated clotting time?
more sensitive
what part of secondary haemostasis is evaluated by prothrombin time?
extrinsic
common
what is prothrombin time sensitive to?
vitamin K dependent factors and rodenticide toxicity
how are APPT and PT assessed?
blood to be sampled into sodium citrate tube and filled exactly to the marked line. (not under or over) and then evaluated straight away at the diagnostic lab
What should be done if APPT and PT samples are having delayed analysis?
if the samples need to be couriered to the lab overnight, they will need to be double spun down to recover the citrate plasma and frozen until transported.
what effect will rodenticide toxicity have on PT and APTT?
PT prolonged before APTT
what clotting factor has the shortest half life?
factor VII (7)
why is prothrombin time so sensitive to rodenticide toxicity?
extrinsic factor 7 has shortest half life and so lack of will be picked up by PT as it assessed extrinsic pathway
what clotting tests can be run in house?
APTT
PT
ACT
what is starting to be used in some veterinary hospitals to assess coagulopathies?
thromboelastography
what is thromboelastography?
shape generated on machine depends on coagulopathy seen
what tube does blood for clotting assessment need to go in?
citrate
what are the areas of specific nursing care for regenerative haemorrhagic anaemia?
Controlling haemorrhage e.g pressure bandaging.
Fluid therapy/bolus.
Oxygen supplementation.
Blood transfusion- monitor for reactions
tailor to specific cause
what must be monitored in patients receiving blood transfusions?
TPR
BP
MMs
CRT
how often should monitoring be performed when patients are undergoing blood transfusion?
every 10 minutes for the first half an hour, then every 15-30 minutes until transfusion is complete
what are the nursing considerations for patients with regenerative haemolytic anaemia?
Fluid therapy
Nutritional supplementation with iron, folic acid and B vitamins. Potentially feeding tube - monitor for aspiration pneumonia.
Patients presenting with this are usually recumbent so padded bedding and regular turning is essential.
Immunosuppressant drugs- barrier nurse.
what should patients with regenerative haemolytic anaemia have nutrition supplemented with?
iron, folic acid and B vitamins
what are the main nursing considerations for neon-regenerative anaemia?
Often secondary to systemic disease such as FeLV of CKD etc so tailor nursing to cause and symptoms.
Potentially blood transfusion needed so monitoring for reactions is vital.
Nutritional deficiency anaemia- feed a diet high in iron, folic acid and B vitamins. Potentially feeding tube in place so general nursing care for this- check negative pressure etc for patency. Monitor for aspiration pneumonia.
describe barrier nursing
Wear PPE when handling patient (gloves, apron etc)
House patient in isolation kennel away from other patients
Wash hands thoroughly before and after contact
what blood tube should samples for platelet count be collected in?
EDTA
how should a slide be prepared for manual platelet count?
Ensure sample fresh and no clots present
Invert tube gently multiple times
Use capillary tube to draw up a small amount of sample, place on to microscope slide
Create a blood smear- ensure of diagnostic quality (feather edge, 50% of slide length)
Stain smear with diff quick
describe how to identify platelets on prepared smear
Scan the feathered edge for platelet clumps at 10x magnification
Identify monolayer using 40x magnification
Increase magnification to 100x magnification with oil immersion to scan for platelets in the monolayer
what magnification is needed to see platelets in the monolayer?
100x magnification with oil immersion
how many fields should platelets be counted in?
at least 10
how many platelets should be seen per field to determine field is adequate for average count?
8-10
how are the number of platelets calculated?
Count the number of platelets in at least 10 fields
Calculate average
Multiple average by 20= estimated platelet count X109/l
what should the average platelet number be multiplied by?
20
what can affect manual platelet count?
falsely decreased if platelet clumps are present
what is seen in this image?
platelet clumps
what is seen in this image?
platelets
what is normal platelet count?
200-500 x10^9/L
what is the purpose of a reticulocyte count?
detect presence of reticulocytes
gives an impression of number of immature RBC in blood and so erythropoesis can be estimated from this
what equipment is needed for staining a slide for reticulocyte count?
New methylene blue solution OR brilliant cresyl blue solution
1x EDTA tube (1ml whole blood) thoroughly mixed
1x Eppendorf test tube
37℃ warm water bath
3x capillary tubes
3x glass microscope slides
Pencil for labelling
how is a reticulocyte slide prepared?
- Wearing gloves, add 3-4 drops of new methylene blue/brilliant cresyl blue solution to 3-4 drops of thoroughly mixed EDTA anticoagulated blood to an Eppendorf test tube
- Mix the contents gently shaking and allow to incubate for a minimum of 10 minutes in a warm water bath at 37℃
- At the end of the ten minutes, gently mix the blood and stain solution
- Using a capillary tube, drop mixture of the blood and stain solution onto each of the three slides, near the frosted edge (as you would when making a blood smear)
- Using your desired technique, create a blood smear
- Label the slides with patient name, patient ID and date
- Allow to air dry. Do not blow to speed up the drying process.
- Once dry, look at the slide under the microscope using oil immersion
what lens should a reticulocyte count be carried out under?
OI
what proportion of new methylene blue should be added to EDTA whole blood when preparing a reticulocyte slide?
3-4 of each (1:1)
how long should the new methylene blue/blood solution be incubated for?
10 mins @ 37 degrees
what PPE is needed when handling new methylene blue?
gloves
goggles
how is a reticulocyte count performed?
- Using x10 lens and then x40 look for reticulocytes (stained RBC with dark blue strands) ideally in the monolayer for ease.
- Count a total of 500 cells and note the number of reticulocytes.
- use formula to calculate percetage reticulocytes
- apply correction factor to give corrected %
- calculate absolute count
what is the formula for percentage reticulocytes?
number of retics x 100%
divided by
total cells counted
what is the purpose of the correction factor in reticulocyte counts?
accurately measure the responsiveness of the bone marrow by taking the patient PCV into account
how is the corrected reticulocyte count calculated?
retic count x patients PCV
divided by
normal PCV for species
how is absolute reticulocyte count calculated?
absolute (x10^9/L) =
observed % retics x RBC count on machine (x10^12/L) x 10
what is normal reticulocyte count in dogs?
0-1.5%
what is the normal reticulocyte count in cats?
0-1% aggregate
up to 10% punctate
identify the reticulocytes on the left and right
L = aggregate
R = punctate
