The cyanosis of peripheral venous engorgement.

Abstract

When the arm is hung down at the side of the body the veins become markedly engorged. Also, there develops a dusky bluish color of the skin of the hand and wrist, extending for a distance up the forearm. Such a state of affairs has usually been assumed to be due to stasis of the blood in the arm.

If the volume flow of blood through the arm is decreased, after a sufficient interval of time, assuming that metabolism progresses normally, there must be a point where the venous oxygen unsaturation is increased above the normal.

In studies using blood taken from the veins on the dorsal surface of the hand, we have found that there is usually a significant decrease of oxygen unsaturation of this blood, when the arm is hung down and immobilized. In eleven experiments, there is a significant decrease of the oxygen unsaturation in six. Of the five remaining, the unsaturation is the same in two cases and decreased in three. In addition, the oxygen capacity of the blood, under these conditions, is usually either increased or remains the same. Of thirteen experiments the capacity is increased in four cases, remains the same in seven and is decreased in two.

It is obvious that such results cannot be explained on the assumption of a simple stasis. The engorgement of the veins suggests that this engorgement extends for some distance towards the arterial side of the vascular bed, at least, into those vessels, venues and capillaries, which are responsible for skin color. Once these vessels have dilated to their maximum degree, there would be a larger volume of blood available for gaseous inter-change, which with a normally progressing metabolism would result in less oxygen extracted from each unit volume of blood to meet tissue requirements.