AN ANALYSIS OF CHANGES IN THE CONTOUR OF THE FEMORAL ARTERIAL PULSE DURING HEMORRHAGIC SHOCK

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Abstract
Pressure pulses were recorded optically from the aorta, the femoral artery, and the dorsalis pedis artery of anesthetized dogs during a step-wise hemorrhage, standard periods of maintained hypotension, and during the course of the circulatory shock that followed reinfusion of all withdrawn blood. The contour of the lateral femoral pulse was analyzed on the assumption that it represented a fusion of a transmitted form of the central pulse with a standing wave created by summated reflections. Several forms of this standing wave were predicted depending upon the degree of elastic tension in the central arterial tree, a factor which at equivalent pressures should be related to the vasomotor status of the vascular bed. Early in hemorrhage the femoral pulse exhibited a sharpening of its peak and a relative increase in pulse pressure. After a very severe hemorrhage changes in the reverse direction were observed. These changes were due to alterations in the standing wave and would indicate an initial compensatory vasocon-striction followed by a secondary passive relaxation of the arteries as blood volume was drastically reduced. Quantitative analyses of the contours of pulses observed in irreversible shock when compared with pulse at equivalent pressures during simple hemorrhage revealed a characteristic distortion of the catacrotic limb of the shock pulses due to a change in the form of the standing wave. This wave exhibited a rapid rise followed by a prolonged fall with a relative reduction in the dicrotic oscillations. Such a wave form was not compatible with generalized vasomotor failure but could be explained as due to vasomotor failure in certain discrete regions. The intestinal arterial bed appeared as the probable site of such a failure.

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