Oxyhemoglobin dissociation curve in anemia

T H E primary function of hemoglobin is the transport of oxygen from the lungs to the tissues. Anemia compromises this transport mechanism and exposes the tissues to the dangers of hypoxia. The fact that patients with slowly developing anemia are frequently symptom-free with low levels of circulating hemoglobin strongly suggests that efficient compensatory mechan-isms are available to provide an adequate supply of oxygen to the tissues. There are two generally recognized compensatory mechanisms: a reduced tissue oxygen tension, which results in more nearly complete extraction of oxygen from the blood, and an increased cardiac output. Both of these mechanisms entail disadvantages—a less than optimal tissue oxygen tension in the former, and increased myocardial work in the latter. A shift to the right of the oxyhemoglobin dissociation curve can be postulated, on theoretic grounds, as a third potentially useful compensatory mechanism. Because of the peculiar shape of the dissociation curve (a flat upper portion that cor-responds to oxygen tensions found in the alveoli, and a steeply descendin