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Y3 MOD clinical pathology > Anaemia in horses > Flashcards

Anaemia in horses Flashcards

1
Q

What is anaemia?

A

A reduction in the circulating red blood cell volume (PCV) or haemoglobin conc

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2
Q

How does anaemia affect tissues?

A

Oxygen carrying capacity of the blood is reduce so hypoxia occurs in tissues

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3
Q

Anaemia develops due to one or more of three patho-physiological mechanisms, what are they?

A
  • Blood loss
  • Increased RBC destruction
  • Decreased RBC production
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4
Q

What is the role of the spleen in horses?

A
  • important reservoir for erythrocytes

- also an important reservoir of platelets

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5
Q

When would it not be appropriate to measure a horses PCV?

A

During or after exercise
When excited
- produce splenic contractions

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6
Q

What are some clinical signs of anaemia?

A
  • Tachypnoea, tachycardia
  • Pallor
  • Exercise intolerance
  • Lethargy
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7
Q

What must you be aware of when looking for signs of chronic anaemia?

A

Chronic or slow onset of anaemia allows physiological compensation so signs may be less obvious

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8
Q

How many litres of blood can a 500kg horse lose before showing clinical signs of hypovolaemic shock?

A
  • Blood volume = 8% of bodyweight = 40L

- 1/3 of that = 13L

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9
Q

What are some clinical signs of hypovolaemic shock

A
  • tachycardia
  • tachypnoea
  • hypothermia
  • pallor
  • prolonged CRT
  • weak pulse
  • cold extremities
  • weakness
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10
Q

What is the normal PCV range of:

  • Thoroughbreds
  • Ponies, warm bloods, donkeys
A
  • 35-45%

- 26-35%

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11
Q

What steps are involved in diagnosing equine anaemia, what questions need to be asked?

A
  • History and clinical exam
  • Acute or chronic?
  • External or internal blood loss?
  • Evidence of a clotting disorder
  • Evidence of haemolysis
  • Lab assessment
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12
Q

An initial laboratory assessment to diagnose anaemia should include which tests?

A
  • Complete blood count, including red cell morphology
  • Total plasma protein
  • Plasma fibrinogen (indicator of a chronic inflammatory disease)
  • Lactate (levels of this increase when there is anaemia)
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13
Q

Reduction of total protein and PCV is indicative of?

A

Chronic blood loss

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14
Q

How does the spleen mask the extent of blood loss in the initial first hours following severe haemorrhage?

A

Injects a concentrated mass of stored erythrocytes into circulation

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15
Q

What is the role of catecholamines as a compensatory mechanism in anaemia?

A

Adrenaline and noradrenaline induce vasoconstriction and increase cardiac output to try and compensate the reduced circulating volume

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16
Q

What is the role of ADH as a compensatory mechanism in anaemia?

A
  • Increases reabsorption of water in the renal tubules and GI tract, as fluid is withdrawn from the interstitium, plasma volume expands
17
Q

Decrease in PCV is not usually seen until how long after haemorrhage?

A

12-24 hours

18
Q

Small nuclear remnants called … are occasionally found in erythrocytes of normal horses and do not indicate increased erythropoiesis

A

Howell-Jolly bodies

19
Q

What peripheral signs of regeneration are rarely seen in horses?

A

Reticulocytes

Polychromasia

20
Q

What acts as an indicator of regenerative anaemia in horses?

A

-Immature RBCs are slightly larger than mature so the mean corpuscular volume goes up slightly

21
Q

How would you test for severe intravascular haemolysis in horses?

A
  • Take a blood sample
  • Spin it
  • Serum is pink – RBCs are being split open and Hb is leaking into the serum
22
Q

Diagnostic evaluation of suspected haemolytic anaemia in horses should include which tests?

A
  • Blood smear evaluation
  • Urinalysis
  • Coombs test
23
Q

What does the Coombs test for?

A

Used to detect antibodies that act against the surface of your red blood cells

24
Q

Will urine colour change to a pink colour in intravascular or extravascular haemolytic anaemia?

A

Intravascular

25
Q

What is the most common cause of anaemia in horses?

A

Haemorrhage due to traumatic or surgical wounds

- acute blood loss anaemia

26
Q

What are some other causes of acute blood loss anaemia in horses?

A
  • Guttural pouch mycosis: fungal infection eats through the wall of the carotid artery
  • Uterine artery rupture
  • Epistaxis
  • Tumours
  • Renal haemorrhage
  • Rib fracture => lung laceration
27
Q

In chronic blood loss, when does anaemia develop?

A
  • Allows the bone marrow to regenerate erythrocytes as they are lost
  • Anaemia only develops once the rate of erythropoiesis is exceeded by the rate of haemorrhage
28
Q

What are some causes of chronic blood loss in horses?

A
  • Parasitic
  • Neoplasia
  • Gastric ulceration
  • NSAID toxicosis
29
Q

What are some causes of haemolytic anaemia in horses?

A
  • Penicillin: Clostridium perfringes infection
  • Injection site abscess
  • Lymphoma
30
Q

What is neonatal isoerythrolysis?

A
  • Foal derives it antibodies from the mares colostrum, the mare has antibodies against the foals blood
  • Mare has been exposed to blood that’s not her own
  • Yellow colour and foal becomes anaemic
  • A Coombs’ test will detect immune-mediated anaemia
31
Q

How can you treat horses with anaemia?

A
  • Identify and eliminate the cause
  • Provide nursing care
  • Ensure adequate tissue perfusion and minimise stress
  • Stop any bleeding
32
Q

When would a horse need to receive a blood transfusion?

A

Should be reserved for instances in which oxygen delivery to tissues is inadequate to support life

33
Q

What must be done if you are unable to stop bleeding?

A
  • ‘Permissive hypotension’: tolerating low blood pressure – as long as brain and heart are perfused
  • Blood transfusion may be ideal
34
Q

If the bleed has successfully been stopped, what are the next steps?

A
  • Replace the lost circulating volume
  • Hypertonic saline
  • Crystalloids
  • Colloids
  • Blood transfusion
35
Q

What % of blood loss from an animal would indicate a transfusion is needed?

A

more than 30%

Y3 MOD clinical pathology (10 decks)

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