Anemia Flashcards
What is anemia? What does it cause? How is it diagnosed?
decrease in red blood cell count or mass
decreased oxygenation of tissues —> clinical signs
PCV/HCT***, RBC count, Hgb concentration
What are the 7 common clinical signs of anemia?
- pale mucous membranes
- lethargy, decreased exercise tolerance
- increased CRT
- tachypnea
- dyspnea (shortness of breath)
- tachycardia
- murmurs caused by increased turbulence
What are 5 non-specific clinical signs of anemia? What are they most likely related to?
- weight loss
- fever
- lymphadenopathy
- polyuria
- polydipsia
underlying illness (that’s making the patient anemic)
What 3 clinical signs of anemia are associated with blood destruction?
- splenomegaly
- icterus (jaundice) of mucous membranes and skin
- hemoglobinuria - Hgb pigment, NOT entire RBC
How does duration of onset of anemia impact the severity of clinical signs?
SLOW onset —> less severe (may adapt to low oxygen levels)
RAPID onset —> more severe
What is the most common 3 step approach to assessing an anemic patient?
- LAB EVALUATION - red blood cell mass (PCV), mean cell volume, reticulocyte count, total protein
- HISTORY - accident leading to blood loss, medications
- PE - pale MM, lethargy
In what 3 ways is anemia classified?
- response of bone marrow - regenerative vs. non-regenerative
- RBC indices - MCV (size), MCHC (chromasia)
- pathophysiologic mechanisms - hemorrhage, accelerated RBC destruction by hemolysis, reduced or defective erythropoiesis
How do horses typically respond when undergoing regenerative anemia?
do not release reticulocytes - release macrocytes
What are the 2 major causes of regenerative anemia?
- blood loss - acute vs chronic
- blood destruction/hemolysis
What is the difference between acute and chronic blood loss causing regenerative anemia?
ACUTE = within hours + hypoproteinemia
CHRONIC = within several days-weeks + iron deficiency
How does acute blood loss present on the erythrogram?
- protein decreases with PCV and will usually return to normal within a week if bleeding is not ongoing
- normal erythrocyte morphology
When does erythrocyte morphology change if the patient is undergoing acute blood lose, making them anemic?
hemangiosarcoma (bleeding due to tumor rupture)
How does erythrocyte morphology change in the case of hemangiosarcoma?
acanthocytes + schistocytes
What are 4 common causes of acute blood loss?
- trauma and surgery
- coagulation disorders
- bleeding tumors (hemangiosarcoma)
- thrombocytopenia (<25,000/µL)
(blood loss does NOT cause thrombocytopenia)
What stimulates RBC production in bone marrow? What happens next?
erythropoietin (Epo)
new reticulocytes are sent into circulation within the next 3-5 days and mature within 1-2 days (7 days total)
What are 3 common causes of chronic blood loss?
(persistent, slow bleeding)
- GI ulcers
- bleeding GI tumor
- blood-consuming parasites: hookworms, whipworms
Where is it most common for chronic bleeding to occur?
intestines
What hookworm of the canine GI tract can cause anemia?
Ancylostoma caninum —> chronic bleeding
What are the causes of iron deficiency anemia in nursing animals and adults?
NURSING ANIMALS - inadequate intake
ADULTS - chronic blood loss
What are the 4 common lab findings in iron deficiency anemia?
- microcytosis of RBC and reticulocytes (decreased MCV)
- increased RDW (anisocytosis)
- normal MCHC
- thrombocytosis
Is iron deficiency anemia commonly regenerative or non-regenerative?
regenerative unless concurrent anemia of inflammatory disease
What is seen on a blood film in iron deficiency anemia?
keratocyte formation with increased central pallor
What 3 chemistry findings are commonly seen with iron deficiency anemia?
- decreased serum iron
- decreased transferrin saturation
- decreased storage iron caused by ferritin and hemosiderin concentrated in bone marrow
How is total iron binding capacity affected with iron deficiency anemia?
usually normal in dogs and cats —> usually increased in other species
What 3 findings are used to diagnose iron deficiency anemia?
- anemia - low PCV/HCT
- microcytosis - low MCV
- low serum iron
What are 3 differential diagnoses should be thought about with microcytosis?
- portosystemic shunts
- breed disposition in Shiba Inus and Akitas
- anemia of inflammatory disease (will have increased storage iron)
10-year-old intact female Yellow Lab with a history of episodes of weakness over the last 4 months.
- 4 months prior: PCV 44%, TP 8.2 g/dL
- blood film: acanthocytes, schistocytes
normocytic, normochromic regenerative anemia
ACUTE —> blood film hints at hemangiosarcoma
5-year-old spayed female Australian Shepherd with a history of vomiting and a ticked abdomen (feeling painful).
- blood film: keratocytes, increased central pallor
- hypoproteinemia
- microcytic hypochromic regenerative anemia
anemia of iron deficiency
What is hemolysis? What are the 2 types?
RBC destruction
- INTRAVASCULAR - within blood vessels or heart
- EXTRAVASCULAR - outside capillary-arterial-venous system unrelated to hemorrhage with phagocytosis of RBCs by macrophages in spleen and liver
What are 5 characteristics of hemolytic anemia?
- splenomegaly
- icterus
- hyperbilirubinemia
- normal total protein
- RBC morphology changes related to the cause - spherocytes, eccentrocytes, Heinz bodies, infectious agents
What is characteristic of intravascular hemolytic anemia?
HEMOGLOBINEMIA - bright red discolored plasma with increased MCHC and MCH
HEMOGLOBINURIA - bright red discolored urine
What are 8 causes of hemolysis?
- immune-mediate hemolytic anemia
- oxidative damage (Heinz body anemia)
- hypophosphatemia
- thermal injury
- zinc toxicosis
- copper molybdenum deficiency (sheep)
- inherited RBC enzyme deficiencies
- RBC parasites, bacteria, and viruses
What is the most common hemolytic anemia in dogs? What are 6 common causes?
immune-mediated hemolytic anemia
- idiopathic
- infection
- drug-induced
- vaccine-induced
- neoplasia
- alloimmune
What are the common infections that induce IMHA in horses? Dogs? Cats?
HORSE - Streptococcus equi var equi (Strangles), Clostridium perfringens
DOGS: Babesiosis, Anaplasma
CATS: Babesiosis, Anaplasma, FeLV
What 2 drugs can induce IMHA in horses? What 2 other drugs are known to induce IMHA?
- Penicillin
- Trimethoprim sulfamethoxazolen
- cephalosporins
- levaminsole
What neoplasias are associated with IMHA?
- lymphoma in horses
- lymphoma/lymphoid leukemia in dogs and cats
What are 2 causes of alloimmune-associated IMHA?
- neonatal isoerythrolysis (NI)
- incompatible blood transfusion where immunoglobulins mark the blood from the donor
What are the 3 characteristic blood film findings with IMHA? What is seen if there is intravascular hemolysis?
- polychromasia/reticulocytosis (regenerative)
- spherocytes in large numbers smaller than RBC lacking central pallor (no red pigment)
- autoagglutination (clumping)
ghost cells —> pale RBCs
How can autoagglutination be differentiated from Rouleaux formation?
- saline dilution test will not dissociate clumping of autoagglutination
- normal in cats and horses
- chain vs clumping
What does this blood film show?
spherocytes indicated by decreased diameter, dense staining, and lack of central pallor - canine IMHA
What test can be used to diagnose IMHA? Is this always necessary?
positive direct Coombs test that assesses for the presence of immunoglobulins (IgM, IgG) or complement (C3b, C3d) on RBC using Coombs reagent consisting of species-specific anti-Ig and/or anti-C3
NO - positive test is supportive evidence of IMHA but there are many false positives and negatives, but clear evidence, like many spherocytes or saline agglutination is enough
What are Heinz bodies? What animals are more susceptible?
denatured hemoglobin on RBCs
CATS have unique Hgb structure and normally have a small % of Heinz bodies naturally on their RBCs
In what 3 situations is it common for cats to develop Heinz body anemia?
- diabetes mellitus
- lymphoma
- hyperthyroidism
Why does Heinz bodies cause anemia?
excessive amounts on RBC membrane causes increased susceptibility for fragmentation and entrapment in the spleen causing them to be phagocytized
What 2 erythrocyte changes denote oxidative damage?
- Heinz body formation
- eccentrocytes
What is commonly used to visualize Heinz bodies?
new methylene blue stain
What 3 plants can cause Heinz body anemia? 5 drugs and chemicals?
PLANTS
1. Allium - onion, garlic
2. Brassica - kale, cabbage, rape
3. Acer rubrum - wilted red maple leaves (not fresh ones)
DRUGS/CHEMICALS
1. acetaminophen (paracetamol)
2. propylene glycol
3. copper toxicosis (small ruminants)
4. zinc
5. selenium deficiency (ruminants)
What is methemoglobinemia? What causes it? What does it result in?
increased methemoglobin in blood
OXIDATIVE DAMAGE - oxidation of Hgb Fe2+ (ferrous) to Hgb Fe3+ (ferric ion)
ferric hemoglobin cannot carry oxygen, making plasma/urine have a dark red discoloration when 30% of Hgb is affected
When does methemoglobinemia become fatal?
if 90% of Hgb has the ferric ion and is unable to carry oxygen
What are 3 causes of methemoglobinemia?
- onion and garlic consumption
- acetaminophen ingestion in cats
- anesthetics, like benzocaine
How does hypophosphatemia cause hemolysis? When does this occur?
low phosphorus —> decreased glycolysis —> reduced erythrocyte ATP and Heinz body formation —> hemolysis
cats with diabetes mellitus causing ketosis
The mechanism of zinc toxicosis causing hemolysis is unclear. How is it thought to cause hemolysis? What 3 things ingested by animals commonly cause this?
oxidative damage
- anti-rash diaper cream
- sunscreens
- coins
How does copper molybdenum deficiency cause hemolysis?
- molybdenum reduces the accumulation of copper in the liver
- with a deficiency, copper accumulates in hepatocytes
- when the sheep becomes stressed (shearing, extreme weather), copper is released into the blood stream
- this increases oxidative injury to erythrocytes and methemoglobin formation
- there is an increase in erythrocyte fragility, causing intravascular hemolysis and hemolytic anemia
In what dogs and cats is it common to find pyruvate kinase deficiency? What 2 lab findings suggests this?
DOGS - Basenji, Beagle, WHWT, Cairn Terrier
CATS - Ayssian, Somali, DSH
- death by 4 y/o
- moderate to marked anemia
- marked reticulocytosis
In what dog is it common to find phosphofructokinase deficiency? What is the most common lab finding? When does it become a hemolytic crisis?
English Springer Spaniels
normal to low PCV
when alkalemic
In what animals is it common to find uroporphyrinogen III co-synthase deficiency? What does this cause? How does this affect RBCs?
cattle
porphyria - inability to synthesize Hgb, allowing an accumulation of uroporphyrin and coproporphyrin in bones and teeth
decreased RBC survival
