Acute and chronic posthemorrhagic anemia.
Anemia resulting from significant blood loss, leading to reduced red blood cell mass and decreased oxygen- carrying capacity.
Classification
I. Acute posthemorrhagic anemia
Etiology
- Trauma (accidents, injuries).
- Surgery-related hemorrhage.
- Gastrointestinal bleeding (e.g., peptic ulcer rupture, variceal bleeding).
- Ruptured ectopic pregnancy or aneurysm.
Pathogenesis
- Immediate blood loss → decreased blood volume → hypovolemia → reduced venous return → decreased cardiac output → hypovolemic shock.
- Hemodilution phase (hours after bleeding):
- Interstitial fluid shifts into circulation to restore volume → hematocrit and hemoglobin decrease.
- 3 Erythropoietin stimulation → bone marrow increases RBC production.
Compensatory mechanisms
- Vasoconstriction (SNS activation) → redirects blood to vital organs.
- Tachycardia, increased cardiac output.
- Increased respiratory rate → improves oxygen delivery.
- Reticulocytosis (after a few days) as marrow responds.
Clinical manifestations
- Signs of hypovolemia: cold, clammy skin; hypotension; tachycardia; weak pulse.
- Pallor.
- Oliguria (low urine output).
- Dizziness, syncope.
- If severe: shock, multi- organ failure.
II. Chronic posthemorrhagic anemia
Etiology
- Gastrointestinal blood loss (most common):
- Peptic ulcer, colon cancer, hemorrhoids.
- Heavy menstrual bleeding (menorrhagia).
- Repeated epistaxis (nosebleeds).
- Parasitic infestations (hookworm).
Pathogenesis
- Repeated small-volume blood loss → gradual iron depletion.
- Iron stores exhausted → impaired hemoglobin synthesis → iron deficiency anemia (microcytic, hypochromic).
- Slow progression allows better circulatory adaptation.
Compensatory mechanisms
- Increased erythropoietin → marrow stimulation.
- Increased iron absorption from gut.
- Chronic blood redistribution to vital organs.
Clinical manifestations
- Fatigue, weakness.
- Pallor.
- Exertional dyspnea.
- Pica (craving non- food substances like clay or ice).
- Koilonychia (spoon-shaped nails), angular cheilitis, glossitis (classic iron deficiency signs).
- May have occult GI bleeding signs (positive fecal occult blood )..