Cardiac output following adrenomedullary deprivation.

This study was performed to determine whether or not the adrenal medulla supports cardiac output and total peripheral vascular resistance after acute hypovolemia. Two groups of anesthetized dogs were studied. The first group underwent right adrenalectomy and the second, left adrenal denervation in addition. Adrenocortical function, as reflected by compound F and dihydroepiandrosterone determinations, was equally maintained in both groups for 120 minutes after hemorrhage. Arterial plasma concentrations of norepinephrine and epinephrine were low in group 2, p greater than 0.05 to greater 0.01. Cardiac index and peripheral vascular resistance were comparable in both groups before and for two hours after the induction of hypovolemia to a mean arterial pressure of 50 millimeters of mercury. The findings indicate that cardiac output and total peripheral resistance do not require adrenomedullary catecholamine release after acute hypovolemia.