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Small Animal Medicine > Regenerative Anemia > Flashcards

Regenerative Anemia Flashcards

1
Q

What is anemia?

A

reduction in red cell mass resulting in decreased oxygen carrying capacity

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2
Q

What is the normal PCV/Hct in dogs and cats?

A

DOGS = 37-55%

CATS = 28-45%

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3
Q

What is indicative of regenerative anemia? How is timing important?

A

increased reticulocytes above the RI —> BM produces and releases the immature RBCs to compensate for demand

reticulocyte formation requires 2-3 days in cats and 3-5 days in dogs - if a blood test is done within this timeframe reticulocytes will be normal/low (pre-regenerative)

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4
Q

How is anemia classified based on morphology?

A

MCV = size - macrocytic, microcytic, normocytic

MCHC = pallor - hypochromic, normochromic (hyperchromic is considered an artifact)

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5
Q

How is anemia classified by severity in dogs and cats?

A

DOGS:
- mild = 30-36%
- moderate = 20-29%
- severe = 13-19%

CATS:
- mild = 22-27%
- moderate = 17-21%
- severe = 10-16%

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6
Q

What are the 2 major causes of regenerative anemia?

A
  1. blood loss - external (wounds, GIT), internal (tumors or coagulopathies cause bleeding into a body cavity), iatrogenic (recurrent blood draws)
  2. hemolysis - RBC destruction caused by the immune system, toxins, infections, or neoplasia

bone marrow is working is able to perceive anemia and produce reticulocytes within 3-5 days

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7
Q

What are the 3 major causes of nonregenerative anemia?

A
  1. pre-regenerative - bloodwork done within 3-5 days of anemia development without time to produce reticulocytes
  2. “extra” marrow - iron deficiency, chronic disease, metabolic disease, kidney disease (decreased EPO)
  3. bone marrow disorders - immune-mediated, infectious, neoplasia, fibrosis, dysplasia
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8
Q

What are the most common clinical signs and physical exam findings associated with anemia?

A
  • pale MM
  • tachycardia
  • tachypnea
  • weakness, lethargy, anorexia, exercise intolerance
  • heart murmur due to decreased blood viscosity

severity varies with duration —> acute = critical, chronic = moderate because the patient has been able to adapt to decreases over time

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9
Q

What are the most common findings in patients with anemia caused by hemorrhage?

A

(decreased platelets or clotting factors)

  • petechia, ecchymoses
  • hematomas
  • melena
  • hematemesis
  • epistaxis
  • hematuria
  • hemarthrosis
  • abdominal distension
  • hypovolemic shock
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10
Q

What are the most common findings in patients with anemia caused by hemolysis?

A
  • icterus - release of bilirubinemia from macrophage destruction of RBCs in the spleen
  • splenomegaly
  • hemoglobinuria (intravascular), bilirubinuria (extravascular)
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11
Q

What are some causes of blood loss that can lead to anemia?

A
  • trauma
  • coagulopathy
  • GI hemorrhage
  • external parasites
  • hematuria (renal) —> idiopathic
  • neoplastic rupture/bleeding —> HSA on spleen
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12
Q

What is indicative of intravascular hemolysis that can lead to anemia? What are some causes?

A

hemolysis within RBC releases hemoglobin into the serum, making it pink

  • IMHA
  • Babesiosis
  • zinc toxicity
  • hypophosphatemia
  • microangiopathic anemia - red blood cell shearing through abnormally small vessels (HSA)
  • inherited erythrocyte abnormalities - pyruvate kinase or phosphofructokinase deficiencies
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13
Q

What is indicative of extravascular hemolysis that can lead to anemia? What are some causes?

A

icterus - RBCs are filtered by the spleen and broken down by macrophages, releasing bilirubin

  • IMHA*
  • Mycoplasma hemofelis (infects RBCs)
  • Cytauxzoon felis (infects RBCs)
  • Heinz body anemia - more mild unless caused by toxins
  • Babesiosis
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14
Q

What are 3 foods that can cause Heinz body anemia?

A
  1. onions
  2. garlic
  3. propylene glycol
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15
Q

What are 6 drugs/chemicals that can cause Heinz body anemia?

A
  1. Acetaminophen
  2. Benzocaine
  3. Methylene blue
  4. vitamin K
  5. DL-methionine
  6. zinc (pennies minted after 1980s)
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16
Q

What are 3 diseases in cats that can cause Heinz body formation in cats?

A
  1. diabetes mellitus
  2. hepatic lipidosis
  3. hyperthyroidism

cause Heinz body formation, not anemia

17
Q

What are some bone marrow causes of non-regenerative anemia?

A
  • immune-mediated —> destruction of precursors
  • neoplasia
  • infections
  • myelodysplasia —> inflammation/neoplasia alters function of BM
  • myelofibrosis —> permanent replacement with or increase of collagen in BM = less cells to produce RBCs
18
Q

What is the most common cause of IMHA? What are some other causes?

A

PRIMARY = idiopathic

SECONDARY = neoplasia, drugs, infection, vaccination

19
Q

What is the pathophysiology of IMHA? What are the 2 possible results?

A

antibodies (IgG, IgM) or circulating immune complexes attach to RBC membrane

  1. macrophages in the spleen and liver use Fc receptors that attach to the antibodies and destroy the RBCs = hyperbilirubinemia
  2. complement attaches to Ig, causing intravascular hemolysis = hemoglobinemia
20
Q

What is the most common cause of hemolytic anemia in dogs? What signalment is most commonly associated?

A

primary IMHA

  • young to middle-aged (6-8 y/o)
  • females > males
  • Cocker Spaniels
21
Q

What is the most common cause of feline IMHA? What are they prone to developing? What signalment is associated?

A

secondary IMHA

pure red cell aplasia, where BM precursors are targeted instead of the mature RBCs in circulation, like in dogs = NON-REGENERATIVE ANEMIA > hemolytic

young males

22
Q

What onset of signs is most commonly associated with IMHA? What signs are commonly seen?

A

acute

  • anorexia, lethargy*
  • tachypnea, tachycardia
  • weakness, collapse
  • pale MM, icterus
  • heart murmur
  • splenomegaly
23
Q

What is the most common type of anemia found on bloodwork in cases of IMHA? What are 2 exceptions?

A
  • severe
  • regenerative (reticulocytosis)
  • polychromasia

NON-REGENERATIVE when there is:

  1. anemia of brief duration
  2. antibodies directed against RBC precursors in the BM
24
Q

What are 3 other laboratory findings other than anemia seen with IMHA? What is most commonly seen in dogs only?

A
  1. autoagglutination due to the presence of antibodies on membranes - dilute blood with saline to prevent nonspecific agglutination or Rouleaux
  2. leukocytosis +/- left shift
  3. thrombocytopenia - immune-mediated thrombocytopenia, DIC, consumption

spherocyte formation

25
Q

What are the 2 most common biochemical findings seen with IMHA?

A
  1. hyperbilirubinemia
  2. elevated liver enzymes, most commonly ALT - caused by increased BILI metabolism, hepatic damage caused by hypoxia, or DIC
26
Q

What are the 3 major differential diagnoses for IMHA?

A
  1. infectious disease - Rickettsia, Babesia, Mycoplasma, Cytaxuzoon
  2. neoplasia - lymphoma paraneoplastic syndrome, malignant histiocytosis lyses RBCs
  3. toxins/drugs - zinc (pennies minted after 1982), onions, garlic
27
Q

What is necessary to diagnose IMHA?

A

regenerative anemia with evidence of hemolysis and one or more of the following:

  • spherocytosis - smaller, rounder, darker RBCs
  • autoagglutination
  • positive Coombs test - RBCs + Ab detected
28
Q

Diagnosing IMHA:

A
29
Q

What are the 3 most common causes of secondary IMHA?

A
  1. infectious - Rickettsia, Babesia, Mycoplasma, Cytaxuzoon
  2. neoplastic -lymphoma, malignant histiocytosis
  3. drugs - Cephalosporins, Sulfas

diagnostics is dependent on individual case findings and compliance

  • rads and U/S recommended to rule out/in neoplasia
  • 4DX Snap for HW, Anaplasma, Lyme, Ehrlichia
  • PCR and serology for Babesia, Mycoplasma, and other tick-borne diseases
30
Q

What are the 3 major complications associated with IMHA?

A
  1. concurrent immune-mediated thrombocytopenia (Evan’s syndrome)
  2. DIC
  3. thromboembolism in lungs, liver, or spleen - fatal hypercoagulable state
31
Q

What are the 5 major aspects to treating IMHA?

A
  1. immune suppression
  2. IVIg adjuvant to block Fc receptors on macrophages and keep them from binding to and destroying RBCs
  3. antithrombotics to avoid PTE
  4. blood transfusions
  5. SECONDARY = remove offending drugs, treat neoplasia/tick-borne disease
32
Q

What immunosuppressive is recommended for IMHA? What are 5 second-line options?

A

Prednisone at immunosuppressive dose (2 mg/kg/day capped at 60 mg/dog) —> larger doses in large dogs are associated with increased clinical signs

  1. Cyclosporine
  2. Mycophenolate
  3. Leflunomide
  4. Azathioprine
  5. Chlorambucil (cats)
33
Q

Why do practitioners commonly use two immunosuppressives when treating IMHA?

A
  • additional drugs are helpful if Prednisone is not working or is waiting to kick in
  • Prednisone side effects can be limited by using an additional medication —> quick results = earlier tapering of Pred (steroid-sparing effect)
  • already behind in the game at the time of diagnosis
34
Q

What antithrombotics are recommended for cases of IMHA? Why?

A
  • Clopidogrel
  • low-dose Aspirin
  • no findings of one having better effects compared to the other

prevents PTE, the major cause of mortality in IMHA patients

35
Q

When are blood transfusions recommended in patients with IMHA? What are the 3 options?

A

when patients are clinical

  1. pRBCs - 1 mL/kg to increase PCV by 1%
  2. fresh whole blood (donor on site) - 2 mL/kg to increase PCV by 1%
  3. stored whole blood - 2 mL/kg to increase PCV by 1%
36
Q

If a patient’s hematocrit is at 15% and is is desired to increase it to 25% with a pRBC transfusion, what amount is recommended?

A

pRBCs = 1 mL/kg to increase by 1%

10 mg/kg —> typically given over 4 hours, since blood can quickly become contaminated at room temperature

Small Animal Medicine (52 decks)

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