True, False, and Latent Anemia
In clinical practice, true pathology must be strictly differentiated from conditions where only the hemoglobin concentration per unit volume changes, rather than its total body mass.
- Hydremia (Pseudo-anemia). This condition involves an increase in the fluid component of the blood (plasma), leading to hemodilution. The total erythrocyte and hemoglobin count remains normal, but their concentration per unit volume drops, creating a false laboratory picture of disease. This most commonly results from massive intravenous infusion of plasma, saline, or other fluids.
- Latent Anemia. This is the reverse situation, occurring against the background of severe dehydration (excessive sweating, profuse diarrhea, intractable vomiting) without adequate fluid replacement. Hemoconcentration develops. Due to plasma loss, the hemoglobin concentration per unit volume may appear normal or even elevated. In reality, the total body hemoglobin content is decreased, but this deficit is masked by blood thickening.
Classification
The pathology may present as an independent nosological entity (e.g., classic iron deficiency anemia) or, much more frequently, as a symptom of other underlying pathological processes.
Main classification principles:
- By origin: primary forms caused by congenital genetic alterations (hereditary), and secondary forms acquired throughout life (symptomatic).
- By leading pathogenic mechanism:
- Posthemorrhagic — resulting from blood loss.
- Hemolytic — caused by erythrocyte destruction.
- Dyserythropoietic — associated with impaired erythropoiesis.
- By the type of hematopoiesis, the process may be normoblastic (normal type preserved) or pathological — megaloblastic.
Acute Posthemorrhagic Anemia
The acute form occurs following massive bleeding from damaged large vessels or heart chambers. Characteristically, it is normochromic, normocytic, and hyperregeneratory.
Risk factors include severe trauma, extensive surgical procedures, gastrointestinal bleeding, and obstetric complications. Acquired or congenital disorders of hemostasis often serve as a predisposing background.
The severity of the clinical picture directly depends on the volume of blood lost, the rate of hemorrhage, and its source. General signs include pallor of the skin and mucous membranes, dyspnea, tachycardia, and a drop in venous and arterial pressure. An important specific marker of acute bleeding is a progressive sensation of dry mouth.
Important nuance: systemic changes are staged. In the early period (first hours and days), reflex vascular compensation is activated. Blood is actively mobilized from physiological reservoirs into the circulation, producing normocytemic hypovolemia. At the same time, plasma and formed elements decrease proportionally. Consequently, hemoglobin concentration and hematocrit may remain normal or drop only minimally, completely failing to reflect the actual severity of the condition at that moment.
Mechanisms of Hemolysis
Hemolytic forms are caused by premature destruction of erythrocytes. This process can follow two main scenarios:
- Intracellular (Extravascular) Hemolysis. This occurs primarily via macrophages in the spleen and, to a lesser extent, the liver. The mechanism is triggered by defects in the erythrocyte membrane. Cells lose their deformability (plasticity), preventing normal circulation; they become trapped within the cords of Billroth (red pulp of the spleen), where they are phagocytosed by macrophages. Clinically, this manifests as enlargement of the spleen (splenomegaly) and liver (hepatomegaly).
- Intravascular Hemolysis. This occurs directly within the bloodstream. Causes include autoimmune and allogenic reactions, exposure to exogenous cytotoxic agents, or mechanical trauma to erythrocytes within capillaries (e.g., by platelet microaggregates or fibrin strands). The main laboratory markers of this state are hemoglobinemia (free hemoglobin in plasma) and a sharp decrease in haptoglobin concentration (the protein that binds free hemoglobin).