Hematology - Anemia Flashcards
What is anemia?
Decrease in circulating RBC mass expressed by reduction in RBC count, hemoglobin, and Hct (PCV)
What is anemia caused by?
Decreased production, increased destruction, and increased loss
What are clinical signs of anemia due to?
Decreased O2 carrying capacity, reduced blood volume, and underlying disease
What do the severity of anemia signs depend on?
Rapidity of onset, degree and cause of anemia, and extent of physical activity
What is the normal response to anemia?
Accelerated erythropoiesis
How does accelerated erythropoiesis occur?
There is reduced oxygen carrying capacity which results in renal hypoxia. Renal hypoxia stimulates erythropoietin (EPO) release
After acute blood loss, dogs increase RBC production to __ to ___ times the normal rate.
6 to 8 times
After acute blood loss, cats increase RBC procution _ to _ fold.
3 to 5
What is the most useful marker of regeneration?
increased number of reticulocytes
What are reticulocytes?
immature non-nucleated erythrocytes
How long does it take reticulocytosis to develop? When does it peak? When does it decline in dogs? Cats?
Takes 2 to 4 days to develop.
Peaks between 4 and 7 days.
Declines at 2-3 weeks in dogs.
Declines in 9-13 days in cats.
What type of reticulocytes do cats have?
Aggregate and punctate
Which feline reticulocyte is present in the circulation for longer?
punctate
Which feline reticulocyte is counted in the laboratory reticulocyte count?
Aggregate
What is the reticulocyte percentage?
The percentage of RBC that are reticulocytes
What reticulocyte percentage indicates regenerative anemia in dogs? Cats?
0-1.0% in dogs, 0-0.4% in cats
How do you calculate the absolute reticulocyte count?
RBC count x RP
At what number of reticulocytes is considered to be a sign of regenerative anemia in dogs?
> 80,000 reticulocytes
At what number of reticulocytes is considered to be a sign of regenerative anemia in cats?
> 50,000 reticulocytes
True or False: Reticuocytes are the only absolute thing that you can use to determine if a patient has regnerative anemia.
TRUE
What are some other indicators of regeneration?
Increased MCV (macrocytic), increased RDW, decreased MCHC (hypochromic), polychromasia, and Howell-Jolly bodies
What is the hallmark of external blood loss? (Hint: it is a triad)
Anemia, hypoproteinemia, and reticulocytosis
What are some signs of a primary hemostatic defect?
Petechiae, ecchymoses, hematuria, melena, and epistaxis
What are some signs of a secondary hemostatic defect?
Hemoabdomen, hemothorax, hematomas, and joint bleeding
What factors can be measured to determine if there is a primary hemostatic defect?
Platelet count and von Willebrand factor (vWF)
What tests can be done to determine if there is a secondary hemostatic defect?
Coagulation times - PT and aPTT
Are there any clues on the CBC of acute bleed anemia?
Shistocytes (DIC and hemangiosarcoma) and possibly decreased platelets
Below what number of platelets are patients at risk for spontaneous bleeding?
below 30,000 platelets/microliter
If the cause of acute (regenerative) anemia is not obvious, what other diagnostics can be done? What should not be done?
Radiographs, ultrasound, and endoscopy
Bone Marrow evaluation is not indicated for a regenerative anemia
How much is the canine blood volume?
90 ml/kg - it is 8-10% of body weight
How much is the feline blood volume?
60 ml/kg - it is 6-8% of body weight
When hemorrhage is greater than 20% of blood volume, what signs occur?
cardiovascular signs
Initially, what clinical signs are present in acute blood loss anemia?
Peripheral vasoconstriction and tachycardia
Why is regional blood flow to the skin and spleen curtailed during early stages of acute blood loss anemia?
To protect perfusion to the brain, heart, and viscera
What occurs when blood loss is greater than 30-40% of the blood volume?
CO decreases, hypotension with cardiovascular collapse, the animal is immobile with rapid/thready pulse, and the skin and extremities are cold
What occurs when blood loss is greater than 50% of the total blood volume?
Shock and death occurs within hours
True or False: Initially PCV and total protein are decreased in cases of acute blood loss anemia.
False - initially PCV and total protein are normal
When do PCV and TP decrease in acute blood loss anemia and why?
2-3 hours after the onset of bleeding, and continuing for 48-72 hours, blood volume replacement occurs by the addition of interstitial fluid
When will total protein begin to rise after an acute bleed?
2-3 days after a beed
Will TP or HCT normalize first after an acute bleed?
TP
When does a CBC return to normal after an acute bleed?
in about 2 weeks
If you have reticulocytosis for more than 2-3 weeks, what should you suspect?
There is an ongoing bleed
Initially, acute blood loss is of what type? (think about MCV, MCHC)
Normocytic, normochromic, and non-regenerative
When does acute blood loss anemia become macrocytic and regenerative?
After 3-4 days
What are the four main objectives to treating acute blood loss anemia?
Stop the bleeding and prevent future bleeding, replace the lost red cells, careful volume rescusitation, and treatment of underlying disorder
A healthy, normovolemic animal may tolerate a HCT of what percentage?
5-10% HCT
Signs of ______ develop much earlier in the hypovolemic, anemic animal.
hypoxia
Where is most iron located and in what form?
Most iron is located in RBC’s as hemoglobin
Where does iron storage occur?
In the spleen, liver, and bone marrow
What is a major cause of iron deficiency anemia?
Chronic external blood loss
Initially iron deficiency anemia is regenerative/nonregenerative.
regenerative
What are some common causes of iron deficiency anemia?
Fleas, hookworms, bleeding GI neoplasia, Ulcerogenic drugs, and frequent phelobotomies
Pica can be found in patients with chronic blood loss anemia. Why?
Due to the iron deficiency
How does chronic blood loss anemia present?
Anemia, decreased Hgb synthesis, microcytes, hypochromasia, +/- thrombocytosis
True or False: Chronic blood loss anemia can be microcytic and hypochromic, or microcytic and normochromic.
TRUE
Why is there decreased Hgb in patients with chronic blood loss anemia?
because of the iron deficiency
What will you see on peripheral blood smear in patients with chronic blood loss anemia?
hypochromia, fragmentation (schistocytes), and keratocytes
If there is anemia with a high platelet count in patients with chronic blood loss anemia, what should you search for?
blood loss
What may a chemistry panel show in patients with chronic blood loss anemia?
low total protein
What chemistry change may be associated with GI blood loss?
Increased BUN
How do we treat chronic blood loss anemia?
Find and correct the underlying cause, correct anemia, correct iron deficiency, withdraw ulcerogenic drugs, control ecto- or endoparasites, surgical resction of tumor
When is a transfusion indicated in patients with chronic blood loss anemia?
With severe anemia or in preparation for anesthesia/surgery to find/correct GI hemorrhage
Patients with chornic blood loss anemia are _____volemic with an ______ cardiac output.
normo; increased
When is iron supplementation indicated?
Only in patients with iron deficiency anemia
What type of iron supplementation is recommended first in patients with iron deficient anemia?
Parenteral (IM iron dextran)
After using parenteral iron supplementation, how can iron be supplemented next?
Orally with ferrous sulfate
How do you treat patients with non-external blood loss anemias?
Autotransfusion - with resorption of approximately 80% of RBCs within 1-2 weeks
What is the normal RBC lifespan in the dog?
120 days
What is the normal RBC lifespan in the cat?
70 days
Hemolysis indicates shortened RBC lifespan due to what?
Intrinsic defect or an extrensic mechanism that leads to premature erythrocyte removal such as antibodies against erythrocytes
What type of hemolysis predominates in hemolytic anemia?
extravascular hemolysis
What does extravascular hemolysis refer to?
erythrophagocytosis in the spleen, liver, and bone marrow
What is extravascular hemolysis?
When RBCs are degraded within macrophages, so no Hgb is released from the cytoplasm
What is intravascular hemolysis?
When RBCs are lysed within the circulation as a result of membrane permeability changes or cellular fragmentation
Is hemoglobinuria and hemoglobinemia associated with extravascular or intravascular hemolysis?
intravascular
Is bilirubinemia and bilirubunuria associated with extravascular or intravascular hemolysis?
extravascular
Why does hemoglobinuria occur during intravascular hemolysis?
When the amount filtered through the kidneys exceeds the limited capacity of the tubule to resorb Hgb
What can cause artifactual hemolysis?
Poor venipuncture technique, prolonged blood storage, exposure to temperature extremes
What clinical signs are associated with hemolytic anemia?
Pallor, weakness, jaundice, pigmenturia - signs can be acute/fulminant or subacute/chronic
Is hemolytic anemia usually regenerative or nonregenerative?
regenerative
What is a common finding on CBC with patients with hemolytic anemia?
spherocytes +/- agglutination
What will you find on a chemistry panel in patients with hemolytic anemia?
Normal proteins and elevated bilirubin