tailieunhanh - Chapter 058. Anemia and Polycythemia (Part 2)

Erythropoietin levels in response to anemia. When the hemoglobin level falls to 120 g/L (12 g/dL), plasma erythropoietin levels increase logarithmically. In the presence of renal disease or chronic inflammation, EPO levels are typically lower than expected for a particular level of anemia. As individuals age, the level of EPO needed to sustain normal hemoglobin levels appears to increase. (From Hillman et al.) The critical elements of erythropoiesis—EPO production, iron availability, the proliferative capacity of the bone marrow, and effective maturation of red cell precursors—are used for the initial classification of anemia (see below). Anemia Clinical Presentation of Anemia Signs and Symptoms Anemia is. | Chapter 058. Anemia and Polycythemia Part 2 Figure 58-2 3 6 9 12 15 Hemoglobin gAfL Some fjucj as K ip rOL 6riunu ld t. St. Langfl E L. Jtiriaicn JL Loicilto Ji 17th Edition http Copyright Th M j. Csmp ni f. Ini. AH tight r l rU d. Erythropoietin levels in response to anemia. When the hemoglobin level falls to 120 g L 12 g dL plasma erythropoietin levels increase logarithmically. In the presence of renal disease or chronic inflammation EPO levels are typically lower than expected for a particular level of anemia. As individuals age the level of EPO needed to sustain normal hemoglobin levels appears to increase. From Hillman et al. The critical elements of erythropoiesis EPO production iron availability the proliferative capacity of the bone marrow and effective maturation of red cell precursors are used for the initial classification of anemia see below . Anemia Clinical Presentation of Anemia Signs and Symptoms Anemia is most often recognized by abnormal screening laboratory tests. Patients less commonly present with advanced anemia and its attendant signs and symptoms. Acute anemia is nearly always due to blood loss or hemolysis. If blood loss is mild enhanced O2 delivery is achieved through changes in the O2-hemoglobin dissociation curve mediated by a decreased pH or increased CO2 Bohr effect . With acute blood loss hypovolemia dominates the clinical picture and the hematocrit and hemoglobin levels do not reflect the volume of blood lost. Signs of vascular instability appear with acute losses of 10-15 of the total blood volume. In such patients the issue is not anemia but hypotension and decreased organ perfusion. When 30 of the blood volume is lost suddenly patients are unable to compensate with the usual mechanisms of vascular contraction and changes in regional blood flow. The patient prefers to remain supine and will show postural hypotension and tachycardia. If the volume of blood lost is 40 . 2 L in the averagesized adult