Hemodynamic characteristics of regional vascular beds in cerebral ischemic pressor responses.

The mode of participation of three vascular beds of the kidney, intestine and skeletal muscles during blood pressure oscillation elicited by what is called a "side pressure exertion experiment" was investigated in anesthetized rabbits. The effect of varied circulating blood volume on their participation was also studied. The route of the blood supply to the brain was surgically restricted to one common carotid artery and the artery was compressed by exerting side pressure on a segment of it. When the side pressure was elevated in steps, the systemic arterial pressure also rose in steps from normal to the maximum, superimposed by an oscillation. During the course of graded elevation of systemic arterial ,ressure, the regional blood flow in the three vascular beds indicated characteristic changes as follows. The mean renal blood flow indicated simply an exponential decrease, the mean intestinal blood flow showed an initial slight augmentation which was followed by an expontential decrease, and the mean skeletal muscle blood flow exhibited a marked increase of up to 120 mmHg of mean arterial pressure, succeeded by an exponential decrease. Hemorrhaging and volume loading diminished the range of the changes in renal and intestinal resistance. Muscle resistance change was strongly intensified by hemorrhage. It is concluded that "post-ischemic reactive hyperemia" distinctly characterized the response of the three peripheral vascular beds in addition to the neurogenic control.