Lect 14 Anemia

Anemia

reduction of the total circulating red cell mass below normal limits; reduces oxygen-carrying capacity of the blood

Usually diagnosed based on a reduction in:

Hematocrit & Hemoglobin Concentration; correlate to total red cell mass

Hematocrit

Ratio of packed red cells to total blood volume

RBC indices (secondary parameters)

Allows for classification of anemia based on red cell morphology; includes MCV, MCH, MCHC, RDW

Iron deficiency anemia is the most common in:

toddlers, adolescent girls, and women of child-bearing age

Anemia is...

Most common nutritional disorder on earth

Maintaining iron balance

no regulated pathway for excretion; normal iron loss occurs via shedding of mucosal and skin; as body iron stroes rise absorption falls

Functional Iron

80-85% of whole body iron; found in hemoglobin mainly, some in myoglobin or enzymes

Storage Iron

15-20% of whole body iron; Needs to be stored because free iron is toxic, It

produces free radical formation

Due to the toxicity of free iron, iron is stored in one of

2 forms

Ferritin and Hemosiderin

Ferritin

- Highest levels in liver, spleen and marrow, skeletal muscles, epithelial cells

- Also in the plasma

- More readily available for use

Hemosiderin

- Intracellular storage in lysosomes

- Only trace amounts are found in the body, mostly macrophages in the bone marrow, spleen, liver

- Iron not readily released for use

Iron Transport

Transported in plasma by transferrin, Delivers iron to cells, including erythroid precursors (marrow) which require iron to synthesize hemoglobin

Iron balance is maintained

by regulating the absorption of dietary iron in the proximal duodenum

Heme iron

animal iron (in Fe2+ state)

nonheme iron

not animal iron (in Fe3+ state)

After absorption there are 2 pathways

1. Iron can be transported to the blood

2. Iron remains stored in intestinal mucosal cells, bound to ferritin

Hepcidin

small peptide that is synthesized and released from the liver in response to increases in intrahepatic iron levels; Inhibits iron transfer from enterocyte to plasma by binding ferroportin

hepcidin negative feedback

When body has enough iron, high hepcidin levels inhibit its absorption

Anemia Etiology

dietary lack, impaired absorption, increased requirement, chronic blood loss

etiology: dietary lack

10 to 15% of ingested iron is absorbed; Average Western diet: 15-20mg

anemia etiology: impaired absorption

diarrhea, fat malabsorption, gastrectomy, lack of dietary absorptive aides, presence of absorption inhibitors in diet

Etiology: Increased Requirement

rapid growth (children), Menses

Etiology: Chronic Blood Loss

Most common cause of iron deficiency in the Western world

Diagnostic Testing

CBC with Differential

Morphology

Peripheral Blood Smear; Small, pale cells; Enlarged zone of pallor (hemoglobin may only be peripheral); Poikilocytosis

Persistent systemic inflammation in anemia

Certain inflammatory mediators, especially IL-6, stimulate hepcidin production by liver; Iron stays in storage pool, not loose for use in marrow