Anaemia in Horses Flashcards
What is the role of the spleen in horses?
- reservoir for erythrocytes
- dynamic reservoir of platelets one-third of the total blood platelets
- A horse’s PCV cannot be accurately assessed during or after
exercise, when excited or when endotoxaemia is present since
these produce splenic contraction
What are the compensatory mechanisms?
- Spleen is an important reservoir for erythrocytes
- Catecholamines - vasoconstriction and increased cardiac output
- Plasma volume expansion by:
– fluid from the interstitium moves into blood
– ADH release means increased
* Water resorption in kidneys
* Water absorption in intestines - Horses do not release reticulocytes
What are the clinical signs of anaemia?
- Clin. signs Often secondary
– E.g. infectious disease, antimicrobial use, neoplasia, - Primary clinical signs of anaemia related to:
– Reduced RBC/Hb
– Inadequate oxygenation of tissues
* Quiet
* Increased Heart rate, respiratory rate
* Pale/dry mucous membranes
* Slow Capillary refill, weak pulses
* Cold extremities
– Depends on rate of loss of RBCs
* Acute (sudden onset) – more severe signs
* Physiological adaptation
How would you classify an anaemia?
- Haemorrhage Regenerative
- Haemolysis Regenerative
- Decreased production Non - Regenerative
What are the steps for diagnosis?
- History and clinical examination
- acute or chronic?
- external/internal blood loss?
- evidence of a clotting disorder?
- evidence of haemolysis?
- initial laboratory assessment should include:
– a complete blood count (CBC),
– total plasma protein
– plasma fibrinogen / serum amyloid A concentration
* indicator of chronic inflammatory disease which may be the
cause for anaemia
– Lactate – indicates oxygenation of tissues. - Red cell morphology should always be evaluated as a routine part of the CBC. Precipitates of oxidised haemoglobin (Heinz bodies), parasites, or abnormal cell shape may aid in defining the cause for anaemia
What are the signs of haemolysis?
- regenerative anaemia without concomitant hypoproteinaemia.
- pink plasma if intravascular + Hb uria, not if extravascular
- May see neutrophilia and regenerative left shift due to intensified erythropoiesis
- Total and indirect bilirubin concentrations may be elevated
What are the signs of acute blood loss anaemia?
– Haemorrhage due to traumatic or surgical wounds (esp. open
castration) is by far the most common cause of anaemia
– Guttural pouch mycosis
– Uterine artery rupture
– Mesenteric artery rupture (strongyle migration) (now rare)
– Epistaxis (rare)
– Tumours - haemangiosarcoma, splenic disease
– Thoracic large vessels rupture in racehorses
– Renal haemorrhage
– Umbilical loss in foals
– Rib fracture (esp. foals)
What are the signs of chronic blood loss anaemia?
– Usually GIT
* parasitic (particularly large strongylosis)
* Neoplasia
* gastric/duodenal ulceration
* NSAID toxicosis
– May be urogenital blood loss e.g. renal, urethral
What are the signs of haemolytic anaemia?
– True immune mediated haemolytic anaemia rare, more likely
secondary haemolytic anaemia
* esp. penicillin (drug bound RBC recognised as foreign)
Clostridium perfringens infection
* injection site abscesses
* lymphoma, other forms of internal neoplasia
– Neonatal Isoerythrolysis
* A Coombs’ test will detect immune-mediated anaemia
What are the blood parasites?
What is the test to detect EIA?
– Blood parasites - babesia
– Infectious Anaemia - EIA, Erhlichiosis
* Pyrexic sick
* A Coggins’ test will detect the presence of Equine Infectious
Anaemia
What are the causes of non-regenerative anaemia?
– Bone marrow disorders e.g. toxic, neoplastic
– Anaemia of chronic disease e.g. renal disease
– Iron deficiency (uncommon)
* usually only if chronic blood loss
– Folic acid deficiency on some meds. E.g sulphonamides,
trimethoprim or pyrimethamine
What is the treatment for anaemia?
- Adjunctive therapy
– Iron (in iron deficient animals)
– Vit B12 in deficient animals
– Anabolic steroids (ns BM stim and Erythropoeitin-mediated)
– corticosteroids in IMHA or drug haemolysis
– VitC or antioxidants for red maple leaf
How would you treat a haemorrhage?
- Stop Bleeding***
– Surgical ligation/haemostats / pressure bandage / packing
– tranexamic acid?
* Lysine analog – inhibits plasminogen to plasmin
* Prevents fibrin degradation - If you are unable to stop bleeding:
– ‘Permissive hypotension’
– Maintain enough blood pressure to deliver oxygen to brain/heart
– Caution not to dilute RBCs and increase haemorrhage by
excessive fluid administration and increase in blood pressure
– Blood transfusion ideal – if unavailable and severe shock then
colloids / hypertonic saline required.
If you have successfully stopped the bleeding what do you do?
– Replace circulating volume:
* Hypertonic saline (7.2%) (4-5ml/kg/10 min = 2 L/500kg)
* Crystalloids - rapid infusion of 40-60 ml/kg
* Colloids – plasma or synthetic colloids – may prolong clotting times
* Blood transfusion
When would you do a blood transfusion in acute blood loss?
– when > 30% blood volume lost
– if clinical signs of hypovolaemic shock
– Increasing lactate (>4mmol/L)
– if PCV < 15%
