Relation of Sodium Balance to Arterial Pressure During Drug-Induced Saluresis

Serial determinations of plasma volume and urinary sodium excretion were determined during saluresis in 20 hypertensive patients. Although the diuretics produced a decrease in plasma volume and an increase in urinary sodium excretion in all patients, there was no direct relationship between the decrease in plasma volume and the fall in arterial pressure. Concomitant administration of dextran solution prevented the reduction in plasma volume but did not prevent the fall in arterial pressure. Similarly, replacement of plasma volume with dextran solution at the peak of hypotension following the diuretics had no effect on the reduced arterial pressure. Concomitant administration of hypertonic saline solution with the diuretic prevented the fall in arterial pressure, and the replacement of urinary sodium loss at the peak of hypotension returned the arterial pressure to control values when the sodium administered exceeded the urinary sodium loss. It would seem that in the hypertensive sodium depleted state a direct relationship exists between arterial pressure and sodium balance. Thus, a positive sodium balance is associated with a rise in arterial pressure, whereas a negative sodium balance is associated with a fall in arterial pressure. The data suggest also that the decreased pressor response during saluresis is due more to the production of negative sodium balance than to a decrease in plasma volume.