Interpreting the Erythrogram Lecture 4

What is anemia?

• Decrease in red blood cells

  • manifested as a decrease Hb, PCV/HCT, RBC count

Clinical manifestations of anemia

• one main cause for these signs

• lethargy, weakness, increase RR, increased HR, pale mm

• Signs are related to decrease oxygen carrying capacity

3 ways anemia can be classified

• Bone marrow response

  • regenerative

  • non-regenerative

• Based on etiology

  • hemolysis

  • hemorrhage

  • iron deficiency

  • production disorders

• Based on erythrocyte indices

  • cell size and Hb concentration

What are the 2 main types of Anemia when based on bone marrow response?

• Regenerative anemia

  • bone marrow is capable of synthesizing RBC’s to restore RBC mass

  • results from

    • hemorrhage (blood loss)

    • hemolysis (destruction of RBCs)

• Non-regenerative anemia

  • decreased production of RBCs by the bone marrow

  • lack of EPO (protein to synthesize red blood cells)

  • defect in erythropoiesis

What are the two main causes for regenerative anemias?

• Hemorrhage (blood loss)

  • trauma

  • neoplasia (ruptured tumor)

  • coagulopathologies

  • THINK “The New Cut” → blood loss and T,N,C

• Hemolysis (destruction of RBCs)

  • occurs secondary to infections, toxins, immune-mechanisms, metabolic causes

Why can accessing total protein help determine if hemorrhage or hemolysis is the cause for a decrease in PCV?

• ↓ PCV + ↓ TP → Hemorrhage (When an animal bleeds, it loses both red blood cells and plasma proteins together.)

• ↓ PCV + Normal TP → Hemolysis (In hemolysis, red blood cells are destroyed inside the body, but plasma (and its proteins) stays in the bloodstream.)

What is a regenerative anemia? What parameter can be accessed to determine if a regenerative response is occurring? Why could testing to soon not reflect a regenerative response?

• Decrease in RBC mass accompanied by evidence of accelerated marrow erythropoiesis

• Reticulocyte count must be > than normal (THINK regenerative → reticulocyte; both start with re)

• Mechanism for regeneration
  – Hypoxemia → stimulation of EPO production by kidneys → signals for marrow
  erythropoiesis
  – response may take 3-5 days, thus a regenerative response is not evident in peripheral blood during this time
  ▪ Testing too soon could lead to false assumption that BM response is non-regenerative

  
  

What are is the key differences between extravascular and intravascular hemolysis?

• Extravascular

  • occurs outside the blood vessels

  • macrophages eat RBCs

  • THINK “e” for eat

  • iron loss is not a complicating factor

• Intravascular

  • occurs inside the blood vessels

  • RBCs burst in vessels

  • iron can be lost if chronic which can limit regenerative response

What color might you expect the plasma to be with intravascular hemolysis, extravascular hemolysis?

• intravascular— plasma will be pink due to hemolysis (hemoglobinemia)

  • THINK “pINk” → INtravascular

• extravascular— plasma will be icteric (yellow/greenish) due to hyperbilirubinemia

What is a non-regenerative anemia? In terms of bloodwork evaluation- what would indicate a non-regenerative anemia?

▪ A decrease in RBC mass secondary to a decrease in RBC production
▪ Lack of reticulocytosis (an increase in the number of reticulocytes (immature red blood cells) in circulation. in response to anemia by increasing RBCs) or an inappropriate low reticulocyte count

What are some GENERAL causes for non-regenerative anemias?

• SUPPRESSION OF ERYTHROPOIESIS (the process of producing red blood cells (erythrocytes))———by…

  • Nutritional deficiencies essential to produce RBC (iron, copper)

  • Lack of EPO (protein to produce erythrocytes (RBCs))

  • inability to utilize iron

  • dyserythropoiesis — caused by an intrinsic defect in DNA, mutagenic agents, lead intoxication

    • prevents proper hemoglobin sythesis

How can regeneration be assessed?

• Reticulocyte Enumeration within peripheral blood

  • Reticulocyte enumeration is a direct window into marrow activity — high counts indicate marrow is trying to compensate, low counts suggest a production problem.

• Bone marrow biopsy/aspiration

  • BM reticulocytes >5% = regeneration in horses

  • Performed in other species when BM dysfunction is suspected

    • lack of reticulocytosis in peripheral blood

    • lack of common endocrine or metabolic causes of nonregenerative anemia

Why must reticulocyte enumeration be accessed in light of PCV (packed cell volume)?

An adequate bone marrow response is indicated when the percentage of reticulocytes is equal to or greater than the expected percentage for the corresponding PCV

• anemia itself affects the apparent reticulocyte percentage

What is erythocytosis?

▪ Erythrocytosis is the increase in the number of red blood cells (RBCs) or hematocrit above normal.

▪ HCT/PCV above the normal range
▪ Clinical signs are secondary to increased blood viscosity
– Sludging of blood leads to poor oxygenation of tissues
– Congestion of retinal blood vessels= poor vision
– Purple mm
– Seizures
– Thrombosis
– Headaches (people)

• THINK “Thick blood → slow flow → tissues suffer/poor oxygenation”
  

Clinical signs that result from an increase in PCV are the result of what? In other words what
does having too many RBCs cause the blood to do that results in the clinical signs that we see

• Root cause of symptoms: hyperviscosity of blood due to excess RBCs.

• Even though oxygen-carrying capacity is increased, sluggish flow reduces effective tissue oxygenation.

• THINK “Thick blood → slow flow → tissues suffer/poor oxygenation”

What is a relative erythrocytosis? What is the treatment of choice for a relative erythrocytosis?

• due to a decrease in plasma component of blood

• secondary to dehydration

• corrected by fluid replacement

• most common cause for increased PCV

What is an absolute erythrocytosis? How do you treat an absolute erythrocytosis?

– True increase in RBC count due to increased
erythropoiesis TOO MUCH BLOOD
– Can be due to
▪ Chronic hypoxemia
▪ Compromise of renal perfusion
▪ Polycythemia vera (chronic myeloid leukemia that only affects
the erythroid lineage)
▪ Hyperthyroidism
– Phlebotomy— removing blood
▪ +/- Transient
– Temporary increase in RBC count due to splenic
contraction