Systemic venous reactivity

Abstract

Bartlestone previously has described a preparation (MVO) for assessing the constrictor response to carotid artery hypotension of the caudal venous bed separated by simultaneous occlusion of the descending thoracic aorta and inferior vena cava (IVC). This preparation was utilized to evaluate the extent to which changes in pressure in the caudal venous bed were influenced by crosscirculation from the active (cephalic) circulation. Observations were presented demonstrating that during MVO opening the caudal aorta into a reservoir decreases IVC and internal mammary (cephalic arterial) pressure, and that jugular infusion elevates superior vena caval (SVC) and cephalic arterial pressures and increases caudal aortic flow. Jugular infusion with the aorta intact increases SVC, cephalic arterial, IVC, and caudal aortic pressures. Further, an elevation of SVC pressure during MVO increases IVC pressure—a response which was not modified by reserpine pretreatment. These results were interpreted as indicating that the stability of IVC pressure during MVO depends upon a constant rate of cross-circulation between the cephalic and caudal vascular beds. In addition, a new experimental method was described by means of which estimates of total systemic venous reactivity can be made during brief periods of total circulatory arrest.