Anemias - definition and classification. Posthemorrhagic anemias
⭐ Anemias - diseases of the blood, having less than normal number of red blood cells or less than the normal quantity of hemoglobin in the blood or both → resulting in diminished oxygen-carrying capacity of the blood
- Blood tests in anemic persons show Hb, Hct, ERC
Classification
Post-hemorrhagic anemias
- Caused by blood loss → lose iron so leads to iron-deficient anemia
- Blood loss may be acute or chronic
Acute blood loss
- Causes = trauma, surgery
- Accompanied by a loss of vascular volume and carries with it a risk of hypovolemia and shock
- RBCs are macrocytic and hyperchromic
- Initially if the loss isn’t great = few/no symptoms
- Hemoglobin and hematocrit levels don’t drop immediately; however hemodilution caused by movement of fluid into the vascular compartment produces a fall in red blood cell count, hemoglobin, and hematocrit eventually
- Transient fall in the platelet count, which may rise to elevated levels within 1 hour
- Reticulocytosis = indicator for low RBC levels
- Immature productions of neutrophils → neutrophilic leukocytosis
- The hypoxia that results from blood loss stimulates RBC production by the bone marrow
Chronic blood loss
- Chronic blood loss does not affect blood volume (so no risk of shock) but instead leads to iron-deficient anemia when iron stores are depleted
- RBCs = microcytic and hypochromic
- Blood loss is over a long period of time (weeks/months)
- Causes:
- GI blood loss (bleeding of gums, hemorrhoids, ulcers, gastritis)
- Abnormal menstrual bleeding - hypermenorrhea, metrorrhagia (abnormal bleeding from the uterus outside the normal menstrual cycle)
- Urinary tract abnormalities
- Reticulocyte count may be normal or only slightly elevated
- Noticeable anemia doesn’t usually develop until after storage iron is depleted and Hb < 80 g/l