Cardiac output and peripheral blood flow during occlusion of carotid arteries

Cardiac output and blood flow to the kidney, hind limb, and splanchnic area were studied in anesthetized dogs during the arterial pressure rise due to carotid occlusion. All the vascular beds studied exhibited an increased resistance to flow. Cardiac output was maintained constant through an increased cardiac work in spite of the increased arterial pressure. This increased cardiac work was reflexly produced as evidenced by the action of the adrenergic blocking agent dichloroisoproterenol (DCI). This drug allowed the reflex vasoconstriction and the consequent pressure rise, but preventing the reflex chronotropic and inotropic sympathetic effects on the heart resulted in a fall of cardiac output during carotid occlusion. It is concluded a) that the reflex increase in vasomotor tone is the main factor in the pressor response to carotid occlusion and b) that the reflex effect on the myocardium is an important factor in regulating cardiac output in this situation.