General Anemia Flashcards
RBC
Lifespan
Phagocytized by
~120 days
Eventually phagocytized in reticuloendothelial system
- Macrophages in the liver and spleen
Accumulated damage to the aging RBC renders it unfit to circulate, leading to destruction - Senescence - RBC component recycling
- Red cell destruction stimulates erythropoiesis
Mediated by EPO
RBC
how much HGB per RBC?
several thousand
Anemia
Definition
Reduction in the volume (hematocrit) of or concentration (hemoglobin) of RBCs when compared to similar values from a reference population
Anemia
Mechanisms of disease
RBCs destroyed ~100 days or less, RBC production can’t keep up and patient becomes anemic
Ineffective erythropoiesis
Insufficient erythropoiesis
Blood loss
Acute blood loss
Chronic blood loss
Hemolysis
Increased RBC hemolysis
Expression of amount (units) for HgB, Hct, RBC
Hgb = expression of amount (g/dL)
Hct = expression of volume (% or decimal fraction)
RBC = expression of number (#/mm3)
erythropoietin (EPO)
general
Where is it produced and what’s it do
Primarily Kidney (90%) & Liver (10%)
Stimulates RBC production when O2 is low (hypoxia)
Hypoxia + EPO = INCREASED RBCs
HGB concentration
general
- In anemia, hypoxic signal in kidneys (mainly) and liver results in ↑EPO.
- As Hct falls, plasma EPO ↑↑↑
- In anemia due to impaired RBC production: erythroid progenitors are unresponsive to ↑EPO.
- In anemia is due to hemolysis or blood loss, elevated EPO levels maximize RBC production.
5 Main Compensatory Responses to anemia
02- Hgb dissociation curve
Left shift
O2 Hgb dissociation curve
right shift
Anemia
classifications
2
Decreased production of RBCs
Accelerated loss of RBCs
decreased RBC production
examples
- Marrow failure
Decreased raw materials
RBC defects
Myelodysplasia (Example: Leukemia) - Renal failure
Decreased EPO - Lack of nutrients (iron, B12, folate).
Due to dietary lack
Malabsorption (pernicious anemia, celiac disease)
Blood loss (iron deficiency)
Bone marrow disorders (aplastic anemia, myelodysplasia, tumor)
Bone marrow suppression (drugs, chemotherapy, irradiation)
Think about the patient
Have we intentionally or inadvertently given a drug that is suppressing the marrow?
Nutrients may be present, but the bone marrow is shut down
Decreased RBC production
Low levels of hormones which stimulate RBC production
Chronic renal failure (low EPO)
Hypothyroidism
Hypogonadism
Think about the patient
Is the patient on dialysis
Are there signs of hypothyroidism or hypoandrogenism?
Decreased RBC production
Anemia of chronic disease/anemia of inflammation
Evolutionary defense strategy of the body to limit availability of iron for invading microbes
Iron studies are normal, but the iron is unavailable to microbes…and to the patient
Accelerated loss of RBCs
Destruction of RBCs
Differentials:
* Inherited hemolytic anemias
Sickle cell disease, thalassemia major
* Acquired hemolytic anemias
Autoimmune hemolytic anemia, TTP/HUS, malaria
* G6PD deficiency
RBCs are not stable during oxidative stress, so they get destroyed
Accelerated Loss of RBCs: Destruction
Primary prevention
Screening
Screening
Infants at 9-12 months age
High risk infants/children any age
Pregnant women
Anemia
Hx of a medical condition known to result in anemia
Tarry stools in a patient with ulcer-type pain,
Known rheumatoid arthritis or renal failure
Anemia Hx
Is anemia recent origin or lifelong?
Recent anemia is almost always an acquired disorder
Lifelong anemia, particularly if positive FHx, is likely inherited
anemia Hx
Ethnicity and country of origin may be helpful
Thalassemias and other hemoglobinopathies are common in patients from the Mediterranean, Middle East, sub-Saharan Africa, and Southeast Asia
Hx
Meds, supplements, other
Medications and supplements
Prescribed and OTC
Use of:
Alcohol (folate deficiency)
Aspirin and NSAIDs (GI blood loss)
History of blood transfusions
Exposure to toxic chemicals in the workplace/environment
Hx
Liver disease
Hypersplenism secondary to portal hypertension may be removing RBCs (and platelets) from circulation
Deficiency of coagulation factors synthesized by liver may be causing blood loss
Aplastic anemia (decreased RBC production) may follow hepatitis
Anemia
Symptoms
Anemia
Signs (8)
RBC INDICES
Anemia:
Hbg, Hct, MCV, MCH, RDW
CBC
Complete blood count:
- Hgb
Protein in RBCs that carries oxygen to tissue - Hct
Volume of RBCs: Volume of blood - MCV – indication of RBC size
Macrocytic, normocytic, or microcytic - MCH – Average hgb content in RBC
Hyperchromic, normochromic, or hypochromic - RDW – indication of RBC size variation
Anisocytosis
why is MCV important?
Morphology Classification
Microcytic anemias( 5)
Microcytic (MCV <80 µ3):
Iron deficiency
Thalassemia
Chronic disease/inflammation
Sideroblastic anemia
Lead poisoning
Morphology Classification
Normocytic
Normocytic (MCV 80-100 µ3):
Acute blood loss
Chronic disease
Hypersplenism
Bone marrow failure
Hemolysis
Morphology Classification
Macrocytic
Macrocytic (MCV >100 µ3):
B12 or folate deficiency
Hemolysis with reticulocytosis
Chemotherapy
Hypothyroidism
MDS
Reticulocyte Count
of immature RBCs released from bone marrow into peripheral circulation
Normal levels 0.5%-1.5%
Increased reticulocyte count
decreased reticulocyte count
additional labs for anemia work up
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