StatPearls-/-ä 2024[Jan]; ä (ä): ä PMID33351438show ga
Anemia is a condition marked by a decrease in the number of red blood cells (RBC), the proportion of hemoglobin, or the collective volume of packed RBCs (hematocrit). The main function of RBCs, or erythrocytes, is to carry oxygen from the lungs to the body tissues and carbon dioxide as a waste product from the body tissues to the lungs back. This process is facilitated by hemoglobin (Hb). A decrease in the number of RBCs transporting oxygen and carbon dioxide in anemia decreases the body's capacity for proper gas exchange. The impairment may result from blood loss, an increase in the destruction, or reduced production of RBCs. Traditionally, the decrease is quantified by the ratio of packed RBCs to blood volume, called hematocrit and hemoglobin concentration. Anemia can be classified according to mean corpuscular volume (MCV), a measure of the average volume of RBCs in a specimen. Low MCV indicates microcytic, normal MCV indicates normocytic, and high MCV indicates macrocytic. Anemia is generally defined as hemoglobin of less than 13.0 g/dL in men and less than 12.0 g/dL in premenopausal women Normocytic normochromic anemia differs from other forms of anemia because the average size and hemoglobin content of the RBCs are typically within normal limits. RBCs typically appear similar to normal cells under microscopic examination, though in some cases, there may be variations in size and shape that equalize one another, resulting in average values within the normal range. Normocytic normochromic anemia most commonly occurs as a result of miscellaneous chronic infections and systemic diseases. Most normocytic anemias appear to be the outcome of the impaired production of RBCs.
StatPearls-/-ä 2024 ; ä (ä): ä
