If the number of erythrocytes is excessive or inadequate, erythrocytes problems would arise. Excessive numbers of erythrocytes result to a condition called polycythemia. When erythrocytes numbers is decreased or hemoglobin levels drop, the condition of compromised oxygen transport occurs resulting to anemia.
Whatever the reason is, when a decrease in the oxygen-carrying capacity of the blood takes place the resulting condition is anemia. This is usually indicated by a hemoglobin levels that falls below the lower limit of its normal range (listed above). Anemia may be the result of the following:
- Decreased number of Red Blood Cells
- Abnormal or deficient Hemoglobin content in the RBCs
As a result, a decline in the blood’s oxygen transport capacity would trigger the various physiologic compensations. The following physiologic compensatory events follow when hemoglobin or red blood cells levels drop:
- Arteriolar dilatation to provide increased blood flow.
- Increased blood flow would result to an elevation of cardiac output.
- Shift to anaerobic metabolism to reduce oxygen compensation and indirectly promote the dissociation of oxygen from hemoglobin.
- Increased renal secretion of erythropoietin to stimulate the marrow to increase erythropoiesis and speed RBC production.
Inability of the body to facilitate the listed compensatory mechanisms would result to a drop in hemoglobin levels to 7-8 g/dl. Thus, signs and symptoms of hypoxia emerge such as the following:
- Paleness or pallor
- Excessive intolerance
Increased red blood cell concentration in the blood leads to a condition cally polycythemia. Polycythemia may be due to:
- An increase in red cell numbers with a normal plasma volume
- Absolute polycythemia
- Normal red blood cell numbers suspended in a reduced plasma volume a condition called relative polycythemia
These conditions would result to an elevated packed cell volume (PCV), hematocrit and the hemoglobin level.
Absolute Polycythemia versus Secondary Polycythemia
In primary absolute polycythemia, an overproduction of erythrocytes by the marrow takes place. Secondary polycythemia occurs when the renal output of eryhthropoiesis is elevated hence, resulting to an increased activity of the marrow. The latter condition is a result of physiologic compensatory mechanism of the tissue to hypoxia. In cases where erythropoietin (EPO) production is increased but no physiologic requirement is present, possible renal tumor is present. Aside from that, smokers may also suffer from secondary polycythemia. Significant levels of carbon monoxide are delivered to the blood when products of combustion are inhaled. Carbon monoxide binds with hemoglobin 200 times than that of oxygen. Thus, presence of this chemical in a smoker’s blood would result to a compromised oxygen delivery and increased erythropoietin secretion in the renal system.