Anaemia Flashcards
Define the term ‘anaemia’
A decreased haematocrit, packed cell volume or haemoglobin
What is a haematocrit?
Calculated value from the mean cell volume, red blood cell count and haemoglobin concentration (provided by automatic analysers)
Can be affected by machine errors
HCT = (MCV x RBC count) + 10
Define the term ‘PCV’
Directly measured value measured as a percentage of packed red blood cells in blood volume
Affected by how RBCs pack together
Normally measured by a person due to machine errors
What is a normal dog PCV?
35-55%
About half the haematocrit should be red
Give 4 clinical signs which can be caused by anaemia
Pale mucous membranes
Lethargy and exercise intolerance
Tachypnoea
Tachycardia
Poor pulse quality
Haemic/Flow murmur
Splenomegaly
Lymphadenopathy
Pain
Pica
Icterus
Melaena
What are the 3 causes of apparent non-pathological anaemia?
Young animals
Anaesthesia
Overhydration
How does anaemia cause a haemic or flow murmur?
Diluted blood is less viscous, so makes a whooshing sound on auscultation
True or false?
The severity of anaemia is linked to their clinical condition
False
Can be helpful during diagnosis as severe anaemia is rarely caused due to chronic disease, but then as chronic disease progresses the severity of anaemia does too
What are the 4 ways to categorise anaemia?
- Severity - not 100% reliable
- RBC indices
- Regeneration
- Other haematology clues
Why do animals with chronic anaemia often look clinically healthier than animals with acute anaemia?
Chronic animals look a lot better on low PCVs than acute animals as they’ve had time to compensate for it
Chronic disease takes up a lot of effort from the body, so the bone marrow struggles to keep up, but not that severe
How are red blood cells categorised?
Size
Colour
Shape
Cellular contents
What is the Mean Corpuscular Volume (MCV)?
Average volume of the red blood cells - will change if large or small red blood cells are present
What is the Mean Corpuscular Haemoglobin Concentration (MCHC)?
Amount of haemoglobin in red blood cells
Dependent on the absolute amount of haemoglobin and cell volume
What do the terms normocytic and microcytic mean?
Normocytic = MCV within the reference interval
Microcytic = MCV below reference interval = small cells
Hyperchromic blood contains high levels of haemoglobin, leading to darker coloured blood. What can cause it to falsely elevate?
Lipaemia
Normally a false increase, so tend to ignore if it occurs
What is the term used to describe red blood cells which are variable in colouration?
Polychromatic
Are hypochromic red blood cells darker or lighter than normochromic red blood cells?
Lighter with less colour
MCHC below the reference interval
Red blood cells start as rubriblasts in the bone marrow. Name the stages that red blood cells go through before they become mature.
- Rubriblast
- Prorubricyte
- Rubricyte
- Metarubricyte
- Reticulocyte
- Mature red blood cell (in circulation)
Stages 1-5 occur in the bone marrow, before reticulocytes enter the blood stream
How many hours does a reticulocyte take to mature in the blood stream?
24-48
What is the name given to any normal, healthy cell that is the immediate precursor of normal, healthy, mature (anucleate) RBCs?
Normoblast - nucleated red blood cell
How does the size of red blood cell precursors and haemoglobin concentration change as they mature?
Maturity results in the cells getting smaller and accumulating more haemoglobin
What does the presence of excess numbers of reticulocytes in the bloodstream mean?
Bone marrow is actively trying to correct the reduced red blood cell number
What term describes red blood cells with a variety of sizes?
Anisocytosis
Name 4 non-specific markers which are RBC indicators more common in regenerative anaemia
Nucleated red blood cells
Basophilic stippling
Howell-Jolly bodies
Heinz bodies
What is the difference between Howell-Jolly bodies and Heinz bodies?
Howell-Jolly bodies: small fragments of non-functional nuclei inside red blood cells; normal in cats and horses or associated with increased red blood cell turnover or splenic disease (fragments removed by the spleen); found within the red blood cell
Heinz bodies: denatured haemoglobin inside red blood cells; result of oxidative damage to erythrocytes; seen right on the edge of red blood cells, and often just outside
Does MCV increase, decrease or stay the same in regenerative anaemia?
MCV increases as reticulocytes are larger than erythrocytes
What is the main cause of high reticulocyte levels in the blood?
Haemorrhage
Haemolysis
What are the 3 main causes of non-regenerative anaemia?
Decreased bone marrow production of erythrocytes
Pre-regenerative anaemia - bone marrow takes 3-5 days to respond to anaemia so acute conditions may initially appear non-regenerative
Chronic haemorrhage or haemolysis - even if it starts regenerative it eventually becomes non-regenerative as bone marrow gives up (run out of iron)
You see a lot of banded neutrophils on a blood smear. What are they?
Younger neutrophils - get more banded as they mature
What is the term given for high numbers of white blood cells?
Leukocytosis
You are looking at a blood smear of a dog with anaemia. There are large numbers of spherocytes. What is a likely cause of this?
Immune-mediated haemolysis
Which cells might you see on a blood smear after a dog or cat has had an intravascular red blood cell injury?
Schistocytes (fragmented red blood cells)
Keratocytes (red blood cells with horns)
What red blood cells would you see after onion toxicity in a dog?
Heinz bodies
Due to heinz body haemolysis or oxidant injury
You have a cat with iron deficiency. What type of cells would you expect to see on a blood smear?
Dacryocytes - teardrop shape red blood cells
Seen in iron deficiency and myelofibrosis (blood cancer of the bone marrow)
When might you see echinocytes (wavy/bubbly/spiky red blood cells) on cytology?
In animals with renal azotaemia or having chemotherapy
What do acanthocytes look like, and when might you see them on a blood smear?
Look like spikier echinocytes
Caused by splenic neoplasia and liver disease
If erythropoiesis is suppressed, do you see regenerative or non-regenerative anaemia?
Non-regenerative
Due to intra-marrow or extra-marrow issues
What are the 3 broad causes of anaemia?
Red blood cell loss - haemorrhage due to trauma or coagulopathy
Red blood cell destruction - e.g. haemolysis
Reduced red blood cell production - by the bone marrrow
Give 2 causes of anaemia due to internal red blood cell loss
GIT disease
Parasites
Pulmonary haemorrhage
Abdominal cavity haemorrhage
Other than trauma, what can cause anaemia due to red blood cell loss?
Coagulopathy
Define the term ‘epistaxis’
Nosebleed
Can cause anaemia through external red blood cell loss (like wounds)
Which of the following isn’t a cause of red blood cell destruction?
1. Nutritional deficiencies
2. Toxicity
3. Infection
4. Immune-mediated
5. Mechanical damage
Nutritional deficiencies
Give 3 causes of reduced red blood cell production by the bone marrow
Genetic
Immune-mediated
Infectious chronic disease/inflammation
Nutritional deficiencies (iron deficiency anaemia)
Myelodysplasia
Does melaena result in acute and spectacular blood loss or mild and chronic blood loss?
Mild and chronic
Also caused by chronic or multiple small wounds and GI or blood-borne parasitism
True or false?
Acute and spectacular blood loss from trauma results in an immediate drop in PCV
False
Quick to drop but not immediate
Deficiency of which mineral can be a result of very prolonged blood loss?
Iron
Why is it that a dog can have severe haemorrhage and a normal PCV?
Spleen is a reservoir of red blood cells - contracts in emergencies to provide a lot of blood
Which tick-borne parasite causes destruction of red blood cells?
Babesia - protozoan parasite
What should you be wary of when doing an autotransfusion on a dog or cat?
Clotted blood from abdomens - had contact with the peritoneum and shouldn’t be autotransfused
Name a common cause of haemolysis seen in dogs and cats
Immune mediated haemolytic anaemia
Describe the pathophysiology of immune mediated haemolytic anaemia
6 possible mechanisms:
- Large amounts of autoantibodies to red blood cell membrane antigens
- Antibodies against an infectious agent attacking red blood cells
- Antibodies against a drug which adhere to red blood cells
- Drug or infectious agent modifies red blood cell antigen or exposes a hidden antigen
- Alloantibodies from mixing of incompatible blood groups (blood transfusion reaction or neonatal isoerythrolysis)
- Idiopathic
Give 3 clinical signs which are seen in Immune Mediated Haemolytic Anaemia
Pyrexia
Pallor
Jaundice
Cardiovascular abnormalities
What might you see on a blood smear from a dog with IMHA?
Spherocytes
Leukocytosis
Thrombocytopaenia
RBC parasites
What is Evan’s Syndrome?
Immune mediated disease which attacks platelets and red blood cells
What occurs when you place a drop of EDTA blood from a dog with IMHA onto a slide and mix it with saline?
Autoagglutination of blood cells on the slide leading to visible clumping
Coombs’ test is more sensitive - tests for antibodies or complement adhered to red blood cells
Give 3 causes of non-regenerative anaemia due to bone marrow problems
Infection
Chronic damage
Neoplasia
Lack of raw materials - chronic iron deficiency
What is the most common form of non-regenerative anaemia in small animals?
Anaemia of inflammation (aka anaemia of chronic disease)
Long associated with functional iron deficiency
Normally normocytic and normochromic
What can cause absolute (true) iron deficiency in small animals?
Most commonly due to chronic haemorrhage = loss of iron-rich haemoglobin
Can be regenerative or non-regenerative
Classically microcytic hypochromic
Name 2 causes of non-regenerative anaemia due to a problem not involving the bone marrow
Chronic kidney disease
Excessive oestrogen
Some types of FeLV
What type of anaemia does a functional deficiency in iron result in?
Normocytic normochromic anaemia as there are less red blood cells in general (no new ones being made)
Enough iron but the bone marrow can’t use it = functional iron deficiency
How can chronic renal failure result in non-regenerative anaemia?
Reduced erythropoeitin production is reduced in advanced renal disease
Erythropoeitin stimulates the production and maintenance of red blood cells
Non-regenerative anaemia due to haemorrhage, haemolysis and decreased or ineffective erythropoiesis can all be caused by what?
Neoplasia
Which 3 endocrinopathies can cause non-regenerative anaemia?
Hypothyroidism
Diabetes mellitus
Hypoadrenocorticism
Which syndrome causes non-regenerative anaemia by making erythropoiesis ineffective?
Myelodysplastic syndrome - group of blood cancers which prevent immature blood cells from maturing
How can liver disease result in non-regenerative anaemia?
Anaemia of inflammation
Abnormal nutrient metabolism
Defective iron handling
Dogs are often microcytic, even if they are not anaemic
Give a brief description of how FeLV can cause non-regenerative anaemia in cats
FeLV can infect haematopoietic precursors
Results in direct suppression of early-stage erythropoietic cells
Anaemia, inflammation and immune-mediated haemolysis
True or False?
Copper deficiency causes non-regenerative anaemia by giving a toxic insult to the bone marrow
False - chemotherapy does this
Name 2 space-occupying diseases of the bone marrow which can cause non-regenerative anaemia
Fibrosis
Neoplasia
Which 3 nutritional deficiencies can cause non-regenerative anaemia?
Copper deficiency
Folate deficiency
Cobalamin deficiency
After taking a history, what are the 3 most important questions that we need to answer to diagnose the cause of anaemia?
How severe is the anaemia?
Is it regenerative or not?
Are there abnormal red blood cells present?
True or False?
Haemorrhage can occur into the muscle when blood is bleeding into the leg
True
Looks like soft tissue damage, but actually blood pooling and much more acute
Seen with tachypnoea and pale mucous membranes
Swollen muscle bellies can be very difficult to detect in fat, 60kg dogs
What makes acute anaemia cause more severe clinical signs than a chronic anaemia of the same PCV?
Compensatory mechanisms present in chronic disease, compared to a sudden loss of circulatory volume/O2 carrying capacity in acute disease
Hypovolaemia
Trauma
Pain
Pyrexia
Acute anaemia more likely to have cardiovascular signs
Animals with acute anaemia are more likely to have severe clinical signs. Which other anaemic animals are likely to suffer more?
Animals with severe anaemia - more likely to result in cardiovascular signs, lethargy and weakness
Animals with concurrent systemic disease - processes (e.g. CKD) are more likely to have adjunct clinical signs and potentially a more severe presentation than those with low level blood loss alone
What are the 3 broad steps taken to treat anaemia?
- Triage and emergency treatment, investigation and stabilisation
- Fluid therapy, blood product transfusion
- Treat (or limit clinical signs of) the specific disease - haemorrhage, haemolysis, infectious diseases, oxidative damage, bone marrow (intra- or extra- marrow)
What are the most important things you can do during emergency stabilisation of a dog with anaemia?
Oxygen supplementation
Temperature management - don’t warm up too quickly if hypothermic as causes peripheral vasodilation and so a decrease in blood pressure
Fluid therapy
Analgesia - reducing pain enables cardiac signs to be more accurate for the condition and not high from pain
Treat cause/concurrent conditions
Emergency surgery may be needed for bleeding haemangiosarcoma, splenic rupture and arterial bleeds
What 4 steps do you do to treat the cause of anaemia +/- concurrent conditions?
Confirm and characterise anaemia - PCV/TP and blood smear
TFAST, radiographs and abdominal ultrasound
Full biochemistry and haematology - helps but takes a while
Infectious disease screening, e.g. 4DX snap test (Ehrlichia, Anaplasma, Heart worm, Babesia) or PCR; blood smear
Why would you give IVFT to patients with anaemia?
Treat hypovolaemia and address tissue perfusion in the peracute period with IVFT
Describe the differences between the blood products available for patients with anaemia?
Whole blood - won’t contain platelets when stored
Packed red blood cells - most common treatment for IMHA as most condensed form of red blood cells
Fresh frozen and frozen plasma - not used for anaemia as no red blood cells; can be used in coagulopathies
Platelets - only in the US; transfusion doesn’t increase platelet numbers
What is the best approach to treating a patient with haemorrhage?
Diagnose and if possible treat coagulopathy
Physically stop the bleeding if possible
Address internal causes, e.g. GI diseases, genitourinary disease or intracavity bleeding
Transfuse if necessary
Which animals are candidates for a blood transfusion?
Animals which aren’t coping cardiovascularly or who have a massive drop in PCV
You have a dog with anaemia due to haemolysis. What must you check first before giving him glucocorticoids?
Ensure there are no untreated infectious causes of the anaemia
Then give immunosuppressive doses of glucocorticoids - first line treatment for IMHA
Name 2 adjunctive treatments that can be used if immunosuppressive doses of glucocorticoids aren’t effectively treating an animals with IMHA
Azathioprine
Mycophenolate mofetil
Ciclosporin
Leflunomide
All of them are immunosuppressants
Other than immunosuppressants, what else should you consider giving a dog with IMHA?
Antithrombic treatment
How is Babesia spread?
Intracellular protozoon which is transmitted by ticks
True or False?
Babesia causes intravascular and extravascular haemolysis
True
Leads to pallor and jaunince
Give 4 clinical signs of Babesia
Pallor
Jaundice
Pyrexia
Haemoglobinuria
Cardiovascular compromise
Weakness
Inappetence
How can you diagnose Babesia?
Blood smear and microscopy - false negatives
PCR test
Which treatment options do you have available to treat Babesia infections?
Imidocarb (unlicensed antiprotozoan)
Azythromycin (macrolide antibiotic)
Doxycycline (tetracycline antibiotic)
Supportive treatment including blood transfusion and liver support
Should show clinical improvement in 1-2 days - treatment may result in remission rather than a cure
What mustn’t you give to a dog with IMHA due to Babesia?
Steroids - IMHA is secondary to an infectious cause
How can you help prevent transmission of Babesia?
Vigilant tick-checking - takes at least 24 hours for transmission of Babesia organisms
Vaccine available, but not licensed in the UK and only partially effective
How can oxidative damage lead to anaemia?
Oxidation of the haem iron to form methaemoglobin
Oxidation of haemoglobin to form Heinz bodies
Which 2 of the following are more likely to cause anaemia due to oxidative damage in cats and dogs compared to farm animals?
1. Zinc
2. Copper
3. Onions
4. Garlic
Onions and garlic, as well as leeks, rape, kale and cabbages - cats and Japanese dog breeds particularly susceptible
Zinc and copper are more likely to cause anaemia in farm animals
What is the main drug associated with anaemia due to oxidative damage in small animals?
Paracetamol (acetaminophen)
Cats especially susceptible, with dogs being more tolerant
A cat comes in with methaemoglobinaemia (brown blood) and anaemia. What is the most likely diagnosis?
Oxidative damage due to paracetamol poisoning
Liver damage can also be extensive
You have a cat with paracetamol toxicity. What is your first line treatment?
N-acetylcysteine - antioxidant used in dogs and cats
Use methionine if acetylcysteine isn’t available
Can give ascorbic acid to cats - reduces methaemoglobin to haemoglobin
What supportive treatment can be beneficial to treating dogs or cats with paracetamol toxicity?
Oxygen therapy
IVFT
Blood transfusion
Fresh frozen plasma or whole blood to manage coagulopathy resulting from hepatic necrosis
Vitamin K1 in acute hepatic necrosis
Antibiotic therapy in acute hepatic necrosis
Name the Rickettsial bacteria transmitted by ticks
Ehrlichia - inside macrophages and monocytes
You have a dog which presents with a mild, ongoing thrombocytopaenia, hyperglobulinaemia, vague depression, pyrexia, weight loss and poor appetite. He also has enlarges submandibular lymph nodes, and petechiae on his gums.
What is a likely diagnosis?
Ehrlichia
Also causes epistaxis and ecchymoses
True or False?
Most acute infections of Ehrlichia are fatal
False - often recover from acute infections, but can progress to a chronic infection state
Which of the following cells are infected by Ehrlichia?
1. Red blood cells
2. Hepatocytes
3. Haematopoietic stem cells
4. White blood cells
White blood cells
True or False? All of the following are clinical signs of chronic monocytic ehrlichia.
Severe thrombocytopaenia, non-regenerative anaemia, emaciation, swelling of hindlegs and scrotum (peripheral lymphadenopathy) and thrombocytopaenia
True
Also other cytopaenias, hyperglobulinaemia (> glomerulonephritis) and thrombocytopaenia (>uveitis, neuro signs)
What is the first line treatment for Ehrlichia?
Doxycycline or imidocarb (unlicensed)
Both cheap and effective
What should you always do after giving oral doxycycline to cats?
Doxycycline should always be followed by water if give orally to cats, as can cause a tracheal stricture
Anything intracellular is probably treated with doxycycline
