2.2 anemia Flashcards
The essence of the pathophysiology is that anemia results from what?
either increased rate of destruction/loss from the peripheral blood or decreased production in the bone marrow
The components of the CBC that relate to anemia are:
-RBC count
-Hematocrit (Hct)
-hemoglobin (Hgb)
-MCV
-MCH
-MCHC
-reticulocyte count
what does MCV tell us about anemia?
that the average red cells are microcytic, normocytic, or macrocytic
What does MCHC tell us about an anemia?
allows us to define normochromic or hypochromic red cells. Red cells are never hyperchromic. Hyperchromicity is an artifact, most often associated with hemoglobinemia or lipidemia.
assess anemia using
- History
- Physical examination
- Complete blood count
- Reticulocyte count
- Total serum/plasma protein
causes of a regenerative anemia
hemolysis, hemorrhage
causes of a non-regenerative anemia
marrow disorder, primary or secondary
what are the signs of regenerative anemia in the blood?
increased Polychromasia / Reticulocytes
increased neutrophils, platelets
increased Anisocytosis, RDW
increased MCV (macrocytosis)
decreased MCHC (hypochromia)
when might we expect icterus, bilirubinemia, or bilirubinuria?
-expected with hemolysis and internal hemorrhage although the accumulation of bilirubin pigments is more often greater with hemolysis.
-Nonregenerative anemias typically have normal bilirubin concentration
how does hydration impact the interpretation of anemia?
A moderately anemic and dehydrated patient may be severely anemic when rehydrated.
in regenerative anemia, what does a low protein concentration point to?
hemorrhage
in regenerative anemia, what does a higher/normal protein concentration point to?
hemolysis
in a non-regenerative anemia, what do unexplained cytopenias point to?
primary bone marrow disorder
in a non-regenerative anemia, what do normal or increased leukocyte and platelet counts point to?
secondary bone marrow disorder
what will we see in acute anemia, prior to regeneration?
-increased serum bilirubin
-blood smear abnormalities
-proteins
-serial hemograms
what species does not have reticulocytosis during regeneration due to anemia?
horse
in regenerative anemias, how are the hematocrit and reticulocyte count related?
inversely
how long after an acute hemolytic or hemorrhagic episode must we wait to see reticulocytes?
It takes 3 to 5 days following an acute hemolytic or hemorrhagic episode to see increased numbers of reticulocytes; peak numbers are not seen for at least a week.
do rubricytes indicate regenerative anemia?
No
-but when there is a potent erythropoietic stimulus a rubricytosis is often present
-The lack of specificity of rubricytes is due to the fact that other hematologic and non-hematologic diseases can cause rubricytosis unrelated to effective erythropoiesis
-For example, rubricytosis is seen with lead toxicity, erythroid leukemias, extramedullary hematopoiesis, tumors of the spleen, and endotoxemia.
why is protein low in cases of hemorrhage? Why not in cases of hemolysis?
Within 24 hours of a hemorrhagic episode there is a significant shift of fluid from extravascular to intravascular locations to maintain blood pressure and adequate tissue perfusion.
The shift of fluid dilutes the plasma protein so that typically external (including gastrointestinal) blood loss anemias are associated with hypoproteinemia.
Hemolysis is associated with loss of red cell mass without concomitant loss of protein.
what are petechial hemorrhages usually due to?
usually due to thrombocytopenia and less commonly due to decreased platelet function. There is a lot of controversy about how low the platelet count must be before one observes petechiation or hemorrhaging.
what can lead to acute hemorrhage?
Trauma
Thrombocytopenia
• Immune
• Infectious
• Drug-related
• DIC
• Bone marrow failure
Coagulation Factor Deficiency
Neoplasia
very low platelet counts are usually due to what? Vs what other possibility?
-more often due an immune mediated mechanism
-Diseases that cause increased consumption of platelets are less likely to decrease the platelet count below 50
is hemorrhage generally a cause of thrombocytopenia? why?
rarely, since the reserve of megakaryocytes in the marrow and the splenic/lung platelet reserve is great and can be mobilized very quickly
lab features of hemorrhage
- Anemia
- Hypoproteinemia
- Reticulocytosis
- Hypochromia if chronic and external
what are the sequleae of chronic external hemorrhage?
> iron deficient erythropoeisis > iron deficiency anemia
what are the hallmarks of iron deficiency anemia?
o Poorly regenerative or non-regenerative
o Microcytosis
o Hypochromia
o Increased Anisocytosis or RDW
o Red cell fragility
• Fragments
• Shape changes
o Lack of marrow iron
chronic external hemorrhage leads to…
the loss of raw materials essential for erythropoiesis and eventually nonregenerative anemia results. The rate-limiting nutrient is iron.
7 causes of hemolytic anemias
Bacterial
Chemical toxicities
Immune mediated
Parasites
Poisonous plants and venoms
RBC metabolic diseases
Fragmentation - DIC
what are common ways that hemolytic anemia is evident on the blood smear?
spherocytes with immune mediated hemolysis, Heinz bodies with various agents that cause oxidative damage, and the red cell parasites,
most common form of hemolytic anemia in dogs. What are the subcategories? How does it work?
immune hemolytic anemia
can be autoimmune or against foreign antigens
-These antigens or immune complexes adhere to the red cell surface; the red cell membrane becomes damaged because of the close proximity of the membrane to antigen/antibody/complement complexes
when will we find hemoglobinemia and hemoglobinuria
intravascular hemolysis
how are red cells removed in most cases of IHA? What is a consequence/ sign of this?
r-emoval of RBCs by monocytes via phagocytosis
-splenomegaly, since a large component of the monocyte phagocytic system is found in the spleen > spleen undergoes hyperplasia in response to hemolysis
The classic CBC with IHA shows what?
-marked anemia
-marked reticulocytosis
-spherocytosis
-mild agglutination
-moderate leukocytosis with a mild left shift
-Some dogs with IHA also have thrombocytopenia, presumably also due to an immune mediated mechanism.
what does the Coombs test do?
-Coombs test is used to support a diagnosis of IHA
-generally detects antibodies adhered to RBC surface
what is the saline test used for?
-saline will disperse rouleaux but not agglutination
why is IHA more difficult to recognize in cats?
cats lack central pallor in RBCs, making spherocytes more difficult to identify
what are heinz bodies caused by?
oxidative stress denatures hemoglobin
how does DIC cause anemia?
hemolytic anemia due to shearing of red cells on fibrin strands in vessels
