[The critical hemoglobin value in the therapy of chronic anemia]

Adequate oxygen delivery to the tissues can usually be assured until the hemoglobin concentration falls below 7-8 g/dl in patients with chronic anemia provided their compensatory mechanisms are not impaired. Such a reduction of hemoglobin concentration is usually tolerated without symptoms at rest. Under increased physical activity or by an underlying impaired function of the lung or the cardiovascular system, adaptation to anemia may not be sufficient. For this reason the impact of anemia and the resulting hypoxemia must be assessed by determining oxygen needs at various levels of physical activity. The clinical assessment for adequate oxygenation of tissues can be sufficiently estimated by simple parameters as tachycardia, dyspnea etc. Benefits from replenishing O2 carrying capacity by transfusion must be always balanced against transfusion-associated risks. Below a hemoglobin concentration of 7 g/dl oxygen transport is impeded and transfusions are necessary to avoid jeopardizing the patient by additional stressful illnesses such as fever.