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Flashcards

Equine Anaemia

Rhiannon Llwyd Management of Disease English 52 cards

Cards in this deck (52)

  1. 1What is the definition of anaemia?Reduction in circulating red blood cell volume (or Hb) - functionally defined as decreased oxygen carrying capacity of blood
  2. 2When does anaemia occur?When PCV reduced below normal for horse's age, breed and use
    thoroughbreds and hot blooded horses = <0.30L/L, lower in cold blooded horses and ponies
  3. 3What are the three pathophysiological mechanisms that cause anaemia?Develops due to one or more of these:
    blood loss, increased RBC destruction (haemolysis) or decreased RBC production
  4. 4What is the role of the spleen in horses?Reservoir for erythrocytes (PCV can increase during exercise or excitement by as much as 0.25L/L), dynamic reservoir of platelets - up to 1/3 total blood platelets retained in spleen
  5. 5Why is it difficult to accurately assess a horse's PCV in some circumstances?Cannot be accurately assessed during or after exercise, when excited or if endotoxaemia since these produce splenic contraction
  6. 6How can onset of anaemia affect clinical signs?Depends on how rapidly it develops - chronic or slow onset allows physiological compensation
  7. 7What do you need to consider when there is blood loss and effect on clinical signs?Does it occurs acutely, chronically, externally or internally
  8. 8What are the clinical signs of anaemia in the horse?The clinical signs are due to lack of oxygenation - tachypnoea, tachycardia, pallor, exercise intolerance, lethargy, weakness - collapse
    May also hear flow murmur - if PCV <0.15-0.18L/L, decreased blood viscosity, increased turbulence
  9. 9What are the clinical signs of hypovolaemic shock?Tachycardia, tachypnoea, hypothermia, pale and dry mucous membranes, prolonged capillary refill time, weak pulse, cold extremities, muscle weakness
  10. 10With acute blood loss, how much blood does a horse need to lose before clinical signs of shock become apparent?Clinical signs of shock become apparent in the horse when 30% of blood volume is lost
  11. 11How can you tell how much blood is lost?measure - improvised measuring cylinder (use syringe, bucket etc) measure loss over time
  12. 12How many litres of blood can a 500kg horse lose before showing clinical signs of hypovolaemic shock?8% BW = blood volume (in athletic animal)
    8% of 500kg animal = 40L (BV)
    They can lose 1/3 of blood volume before going into hypovolaemic shock = 13L
    (this is approximately a full bucket)
  13. 13What other clinical signs of anaemia may relate to the underlying disease process or haemolysis?Underlying disease: Signs of haemorrhage, pyrexia, anorexia, weight loss
    Haemolysis: icterus, red urine
    May also get effective anaemia from failure of Hb to carry O2 e.g. methaemoglobinaemia or cyanosis
  14. 14What clinical signs may accompany haemolysis?Fever, icterus and/or pigmenturia
  15. 15What clinical signs may signal chronic blood loss?Epistaxis, haematuria or melaena (rare in the horse - as they are hindgut fermenters)
  16. 16What clinical signs suggest an underlying disease process?Anorexia, lethargy and weight loss in association with anaemia
  17. 17What's the normal PCV for thoroughbreds?35% - 45%
    very large variation in one species
  18. 18What's the normal PCV for Ponies and Draft breeds (including warmbloods, minis and donkeys)?26% - 35%
  19. 19What are the first 5 steps of diagnosing anaemia?1. History and clinical examination
    2. acute or chronic?
    3. external/internal blood loss?
    4. evidence of a clotting disorder?
    5. evidence of haemolysis
  20. 20What should the initial laboratory assessment include?A complete blood count, total plasma protein (useful in evaluation of hydration status, and may provide clue to cause), plasma fibrinogen concentration (indicator of chronic inflammatory disease which may be cause of anaemia)
  21. 21Why should red cell morphology always be included as part of complete blood count?Precipitates of oxidised haemogolbin (heinz bodies), parasites or abnormal cell shape may aid in defining cause for anaemia
  22. 22Why are the red blood cell indices not very useful in horses?Because peripheral erythrocytes are nearly always mature
  23. 23What are the compensatory mechanisms for anaemia - spleen?The spleen masks the extent of blood loss for several hours post-haemorrhage by injection of conc mass of stored erythrocytes into circulation
  24. 24What are the compensatory mechanisms for anameia - catecholamines?Catecholamines induce vasoconstriction and increase cardiac output
  25. 25What are the compensatory mechanisms for anaemia - how is plasma volume expanded?Expanded by withdrawal of fluid from the interstitium, increased resportion of water in the renal tubules and from GI tract via ADH
    fluid movement into the vascular system continues at a decreasing rate for up to 72 hr
  26. 26What are the compensatory mechanisms for anaemia? (Decreased TPP)decline in the TPP can be measured within 4-6 hr of the insult
  27. 27What are the compensatory mechanisms for anaemia? (decrease in PCV)Decrease in PCV usually not seen until 12-24hrs post haemorrhage when plasma volume expansion > compensatory effect of splenic contraction
  28. 28How do you diagnose acute blood loss?Based on history of recent haemorrhage, clinical signs an deventual development of anaemia accompanied by hypoproteinaemia
    - care if reduced PCV + increased TPP due to haemoconcentration, anaemia may be more sever than the PCV indicates
    - reduction of both TPP and PCV suggestive of chronic blood loss
  29. 29How would you diagnose regenerative vs non regenerative anaemia?Peripheral signs of regeneration such as reticulocytosis and polychromasia rarely occur in horses, serial PCV in horses (days to weeks) (may see very mild anisocytosis in regenerative samples), bone marrow evaluation may be required to confirm nonregenerative myeloid disorders
  30. 30What are Howell-Jolly bodies and when would you see them?Small nuclear remnants, occasionally found in erythrocytes of normal horses and do not indicate increased erythropoiesis
  31. 31How would you rule haemolysis in or out?Regenerative anaemia without concomitant hypoproteinaemia
    - pink plasma if intravascular + Hb uria, not if extravascular, may see neutrophilia + regnerative left shift due to intensified erythropoiesis, total and indirect bilirubin concentrations may be elevated
  32. 32What would you do in a diagnostic evaluation of suspected haemolytic anaemia?Should include thorough blood smear examination, urinalysis, Coomb's test and poss Coggin's test
    (note dip stick on urine will not differentiate Hb and Mb)
  33. 33How would you rule out or in haemolysis using a smear?Spherocytes, heinz bodies (oxidised Hb) - in some horses with immune mediated anaemia, saline agglutination, erythrocyte osmotic fragility and Coombs test
  34. 34How out would you rule haemolysis in or out?May see increased free Hb, MCH, MCHC and decreased (<3) PCV:Hb ratio
  35. 35What is actue blood loss anaemia and how does it occur in horses?Haemorrhage due to traumatic or surgical wounds = most common cause of anaemia
    Guttural pouch mycosis, uterine artery rupture, mesenteric artery rupture, epistaxis, tumours (haemangiosarcoma, splenic disease), thoracic large vessels rupture (racehorses), renal haemorrhage, umbilical loss in foals, rib fracture (foals)
  36. 36When would you see coagulopathies in horses?Rare - usually DIC consumptive coagulopathy secondary to sepsis, severy systemic inflammation sv inherited, secondary to liver disease, thrombocytopenia ir rare
  37. 37What is chronic blood loss anaemia and how would it present?Allows BM to regenerate erythrocytes, anaemia only develops once rate of erythropoiesis exceeded by rate of haemorrhage, gradual tissue hypoxia allows physiological adaptation so clinical signs of anaemia masked until PCV <0.15L/L
  38. 38What are the causes for chronic blood loss anaemia?Usually GIT = parasitic, neoplasia, gastric/duodenal ulceration, NSAID toxicosis
    May also be urogenital blood loss e.g. renal, urethral
  39. 39What are the different types of haemolytic anaemia and which would you see more often in horses?True immune mediated haemolytic anaemia rare and more likely to be secondary haemolytic anaemia = penicillin (drug bound RBC recognised as foreign) - clostridium perfringens infection, injection site abscesses, lymphoma, other forms internal neoplasia
  40. 40Neonatal Isoerythrolysis - how would you test for immune mediated anaemia?Coombs' test detects immune mediated anaemia
  41. 41Name some other causes for haemolytic anaemia in the horseBlood parasites (babesia), infectious anaemia - EIA, Erhlichiosis (Pyrexic sick, Coggins' test will detect presence of EIA), oxidant induced haemolytic anaemia
  42. 42What are the reasons for non-regenerative anaemia in horses?BM disorders (toxic, neoplastic), anaemia of chronic disease (renal disease), iron deficiency uncommon (usually only if chronic blood loss), folic acid deficiency on some meds (sulphonamides, trimethoprim, pyrimethamine)
  43. 43What are the treatment aims?Identification and elimination of the cause, provision of nursing care, ensuring adequate tissue perfusion and minimising stress
  44. 44When should blood transfusion be done?Should be reserved for instances in which oxygen delivery to tissues is inadequate to support life - occurs at higher PCV if anaemia develops rapidly
  45. 45What's the most important thing to do when treating anaemia?Stop the bleeding!!!
  46. 46How would you control the shock when treating?Hypertonic saline (7.2%), 4-5m/kg/10mins = 2 L/500kg, crystalloids - rapid infusion of 40-60 ml/kg, colloids - plasma or synthetic colloids
  47. 47When would you not want to give colloids?You would want to give them for blood loss as you've also lost protein but wouldn't want to give colloids with haemolytic anaemia
  48. 48Why would you give colloids and what kind of colloids would you give?Plasma or synthetic colloids e.g. hydroxyethyl starch (hetastarch, HES) 6%, 10ml/kg (2-5L/500kg horse), have long half life, do not overdose as will prolong clotting times, dextrans more likely to cause clotting disorders?
  49. 49Name some Hb containing products used as treatment?Oxyglobin, haemopure
  50. 50What is adjunctive therapy?Iron (in IDA), Vit B12 in deficient animals, anabolic steroids, corticosteroids in IMHA or drug haemolysis, Vit C or antioxidants for red maple leaf
  51. 51When would you want to give blood transfusion in acute blood loss and chronic blood loss?Acute: when >30% blood volume lost, if clinical signs of hypovolaemic shock, if PCV <15%, note internal haemorrhage there is recycling of up to 2/3 RBCs and most of protein
    Chronic: if PCV <12%
  52. 52How much blood would you want to give a horse during blood transfusion?BV = 8% BM or 80ml/kg, 500kg horse (0.08x500=40L), deficit = ((normal Ht - animal Ht)/(normal Ht)x(0.08x500)) = ((35-10)/35))x40 = 28L
    Administer 30-50% deficit = 8-10L
    BUT in reality - better to have blood all from one horse and so limited to no of L - can only get 2 bags 3L = 6L from one horse

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Management of Disease (General Weeks 1-6) Flashcards on Equine Anaemia, created by Rhiannon Llwyd on 17/10/2019.
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Rhiannon Llwyd
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