Evaluation of Erythrocytes: RBC Indices Flashcards Preview

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Flashcards in Evaluation of Erythrocytes: RBC Indices Deck (17)
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1

MCV

mean cell volume 

uses erythrocyte population histogram and/or calculation - check with film!

2

MCH

mean cell hemoglobin, determined by calculation, depends on erythrocyte size and internal hemoglobin concentration

 

NOT GENERALLY USEFUL

3

MCHC

mean cell hemoglobin concentration

determined by cacluclation 

use of electronically determined HCT makes it less precise

4

RDW

red cell distribution width

coefficient of variation of erythrocyte volumes and an electronic measure of anisocytosis 

5

MCV increases _______ (slower/faster) than reticulocyte counts in response to hemolytic anemia. 

slower

6

What is spurious macrocytosis? What causes it?

autoagglutination of erythrocytes

caused by: prolonged blood storage before assay, persistent hypernatremia (dogs and cats), hypothalamic lesion

7

Reasons for seeing microcytosis in animals

  1. chronic iron deficiency anemia
  2. portosystemic shunts, primarily in dogs
  3. anemia of inflammatory disease
  4. cats with hepatic lipidosis
  5. japanese breed dogs (akita and shiba) w/o anemia
  6. inhibitors of heme synthesis (ie. lead and chloramphenicol toxicity, vitamin B6 deficiency)
  7. storage iron depletion from increased erythropoiesis
  8. copper deficiency
  9. myeloproliferative disorders
  10. familial dyserythropoiesis in English Springers
  11. Herditary elliptocytosis

8

What does a high MCHC value indicate?

  • NOTHING. 
  • no such thing as "hyperchromic" - always an artifact
  • intravascular hemolysis
  • in vitro hemolysis
  • treatment with cross-linked Hb
  • Heinz bodies in RBCs
  • lipemia
  • erythrocyte agglutination in electronic cell counters

9

What do low MCHC values indicate?

regenerative anemias, especially when high numbers of reticulocytes are present

chronic iron deficiency anemia

hereditary stomatocytosis in dogs

abyssinian and somali cats with erythrocyte osmotic fragility

spurious in some dogs and cats with persistent hypernatremia

10

What does an increased RDW indicate?

  • anemias with increased numbers of large reticulocytes
  • iron deficiency anemia with increased number of microcytes
  • erythrocyte fragmentation 
  • after blood transfusion - different sized cells
  • dyserythropoiesis
  • hereditary stomatocytosis
  • spuriously increased - platelets counted, agglutination etc. 

11

What situations cause increased/decreased serum iron concentrations?

increased: hemolytic anemia, glucocorticoids in dogs and horses

decreased: iron deficiency, anemia due to inflammatory dz, portosystemic shunts, glucocorticoids in cattle

12

What does serum ferritin concentration correlate with? What does an increase/decrease tell you?

correlates with total body iron stores

decreased = iron deficiency

increased = iron overload, hemolytic anemia, inflammation, histiocytic sarcoma complex, transiently in exercising horses

13

Cyanotic appearing skin tells you...

hypoxemia with low pO2 in arterial blood

methemoglobinemia with normal pO2 in arterial blood

methemoglobin spot test vs. arterial blood gas measurement to determine which

14

What color is methemoglobin in venous blood?

brown - use spot test to determine 

15

Causes of methemoglobinemia

  • administration or consumption of oxidant drugs that can also cause heinz bodies
    • acetaminophen, benzocaine, phenazopyridine (dogs and cats) 
    • copper toxicity (sheep and goats)
    • red maple toxicity (horses)
    • nitrate toxicity in ruminants
  • ​hereditary erythrocyte methemoglobin reductase deficiency (dogs, cats, horses)

16

Clinical signs of methemoglobinemia

cyanotic appearing skin and MM (may not notice in pigmented animals)

decreased exercise tolerance

lethargy, ataxia, rapid HR, rapid RR

coma-like state (above 80% methemoglobin)

17

What is a clinical sign of toxicity leading to methemoglobinemia in cats with acetaminophen toxicity?

subcutaneous edema