Regulation of Arterial Pressure

Three anephric patients were studied during sequential periods of normal hydration and overhydration. The increase in arterial pressure caused by the overhydration (+ 7% of body weight) was associated with an increase in peripheral resistance (+ 21.1%, P < 0.01). The elevation of peripheral resistance was preceded by an increased cardiac output (+ 22.3%, P < 0.02) which then fell part way to control levels (+ 13.2%, P < 0.05). Return to normal hydration resulted in return of all variables to control levels. The fall in peripheral resistance was preceded by a transient fall in cardiac output to below control levels (5.6%, not significant). With both normal and elevated pres-