In this VETgirl online veterinary continuing education blog, Dr. Garret Pachtinger, VMD, DACVECC reviews anemia in veterinary medicine. How should you classify the anemia, the underlying cause, and determine what your list of differential diagnoses are?

TIP 1: As simple as it gets, anemia can be classified into three categories:

• Blood loss
• Hemolysis (destruction)
• Decreased production

Classification into one of these three categories is not simply academic, rather it allows the clinician to form a more targeted differential list for both the diagnostic workup and communication with the client.

TIP 2: Although fancy and more expensive diagnostics exist, one cannot ignore the cost-effective practicality of a simple packed cell volume (PCV) and total solids (TS) to evaluate anemia. For example, if the PCV and TS are both low, acute blood loss should be suspected. In contrast, a low PCV with normal total solids would be consistent with hemolysis or decreased red blood cell production. Here is a chart with a few examples of how PCV and TP together can help direct your diagnosis and treatment plan:

PCV TS VETgirl blog Garret Pachtinger chart

TIP 3: Don’t forget a blood smear! If the blood smear shows polychromasia and anisocytosis, this often indicates a regenerative response. Conversely, the lack of those cells may indicate a non-regenerative response. A blood smear can also help evaluate WBC morphology and an estimated platelet count.

TIP 4: A slide agglutination test is another cost-effective test you should have in your anemia “toolbox.” Especially if hemolysis is suspected (low PCV, normal TP, icteric serum/patient). To perform a slide agglutination, a drop of anticoagulated blood from a purple top tube or capillary tube is mixed with a drop of 0.9% NaCl.

TIP 5: Don’t forget to simply look at your patient! Ask yourself, “does the patient look way better than you would expect with a PCV that low?” Simply put, clinical signs vary depending on severity and acute or chronic occurrence of the anemia. If the patient has a PCV of 12 and is happy, BAR, grooming, eating…then you are likely dealing with a more chronic and non-regenerative anemia!

TIP 6: A regenerative response is not immediate. It takes up to 3 days after the anemia develops for the bone marrow to respond. A reticulocyte count > 80 × 109/l is indicative of regeneration.

TIP 7: Heinz-body anemia commonly occurs secondary to toxin exposure including zinc, garlic, onion, or acetaminophen. Zinc is the main metal component of pennies, not copper and any patient showing a Heinz-body anemia should be evaluated for penny ingestion.

TIP 8: There is no specific number in which every patient should receive a red blood cell transfusion for anemia. Simply put, there is no “transfusion trigger.” Each patient must be assessed individually for factors that would warrant a transfusion including hemoglobin concentration, hematocrit, CvO2, lactate concentration, lactate, blood pressure, heart rate, pulse quality, etc.

TIP 9: Blood transfusion therapy is not without risk. Although most are familiar with more subtle transfusion reactions (e.g. transient pyrexia, hemolysis, transfusion-associated circulatory overload (TACO), facial edema, vomiting), TRALI, defined as transfusion-related acute lung injury, is another concern. TRALI is defined as new acute lung injury that occurs within 6 hours of transfusion of one or more blood products resulting in hypoxemia and non-cardiogenic pulmonary edema.

TIP 10: Don’t forget the importance of fluid therapy. Intravenous fluid support will provide improved circulation of the red blood cells that remain. If fluid therapy alone does not improve tissue oxygenation and clinical signs, a blood transfusion should be considered.

  1. Shanoob says:

    If iv fluids r being administered in an anaemic dog , won’t there b a hemodilution inturn leading to shock?

    • VETgirl says:

      The use of IV fluids will cause hemodilution, but most patients still need IV fluids – they also have interstitial depletion. It doesn’t affect the circulating number of RBC.

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