SUMMARYThe sequence of hemodynamic events during periods of salt-and water-loading was studied in anephric patients and those with end-stage kidney disease. The 10 patients studied showed four different sequential hemodynamic patterns: 1) no significant increase in blood pressure (BP) in two patients; 2) increase lit BP associated with an increase in cardiac output and without change in total peripheral resistance in two patients; 3) increase in BP associated with an increase in total peripheral resistance from the beginning without an increase in cardiac output in fire patients; and 4) increase in BP associated with an initial increase in cardiac output followed by an increase in total peripheral resistance in one patient. There was a significant positive correlation between BP and blood volume and between BP and total exchangeable sodium in the patients in whom salt-and water-loading increased the BP. It is concluded that during salt-and water-loading an initial rise in cardiac output is not necessary to increase BP and that a sustained rise in cardiac output does not always increase the total peripheral resistance. Mechanisms other than whole-body autoregulation play a role in increasing BP during salt-and water-loading in patients deprived of renal excretory function. In patients with end-stage kidney disease, the most important factor responsible for this increase in total peripheral resistance are the vasopressor function of the kidneys 1 ' f and the increase in body salt and water.2 " 1 In anephric patients, salt and water balance plays a major role in the regulation of BP.2 -*~8 The final effect of salt-and water-loading in anephric patients has been found to be an increase in total peripheral resistance.2 '" The precise mechanism by which expansion of body fluid increases BP remains uncertain, however. Received January 9, 1979; revision accepted September 24, 1979.In our previous experience with weekly hemodynamic studies, the BP increase induced by salt-and water-loading was associated with an increase in total peripheral resistance.2 Under similar experimental conditions, Coleman and co-workers 8 reported that the initial hemodynamic change observed during saltand water-loading was an increase in cardiac output; an increase in total peripheral resistance followed.' These findings were interpreted as demonstrating that during the development of this hypertension the initial increase in cardiac output results in perfusion of tissues above their metabolic needs, which in turn elicits myogenic constriction of peripheral vessels, thereby producing an increase in total peripheral resistance. 810 According to this theory, the initial increase in cardiac output is the cause of hypertension, and the subsequent rise in total peripheral resistance is the result.8 -10

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1. Patients with end-stage renal disease and anephric patients underwent expansion and depletion of body fluids with salt and water. This resulted in four different sequential haemodynamic patterns: (i) no significant increase in blood pressure; (ii) increase in blood pressure associated with a rise in cardiac output and no effect on total peripheral resistance; (iii) increase in cardiac output followed by a rise in blood pressure and total peripheral resistance; (iv) increase in total peripheral resistance and blood pressure without significant changes in cardiac output. 2. It is concluded that an initial rise in cardiac output is not necessary to increase blood pressure in either anephric man or patients with end-stage renal disease.

Serial hemodynamic studies have become increasingly important in hypertension research. These studies have been accomplished using the A-V shunt. The progressive decline in the number of A-V shunts in favor of the A-V fistula has limited the number of patients available for study. Although the A-V fistula can be used to measure cardiac output, the intra-arterial blood pressure cannot be measured through it. The present paper describes a technique formeasuring both the cardiac output and direct intra-arterial blood pressure using the bovineartegraft.