Venous oxygenation and circulatory responses to oxygen inhalation in acute anemia

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Abstract
Studies were made in 20 dogs of the effects of acute normovolemic anemia on venous oxygenation and systemic oxygen transport. Ten dogs were given 100% oxygen to evaluate the circulatory effects of oxygen administration before and after anemia was induced. In anemia mean mixed venous oxygen tension decreased 2.3 mm Hg and a fall in venous oxygen saturation of 4.2% occurred. No shift in the oxyhemoglobin dissociation curve was demonstrated when oxygen tension was corrected for pH change. The administration of 100% oxygen to dogs with normal hematocrits resulted in a significant decrease in heart rate and cardiac output and a rise in peripheral vascular resistance. In anemia 100% oxygen raised mixed venous oxygen tension well above control values and systemic oxygen transport was increased nearly to normal amounts; these changes, however, did not modify the circulatory responses to anemia. It is concluded that the circulatory adjustments that are caused by acutely induced anemia do not result from a reduction in systemic oxygen transport or mixed venous oxygenation.