Relation of Extracellular Fluid Volume to Arterial Pressure during Drug-Induced Saluresis

The immediate fall in arterial pressure following furosemide in the 17 hypertensive patients studied was asociated with a decrease in plasma volume, cardiac output, and extracellular fluid volume, and an increase in urinary sodium excretion. A glucose infusion administered at the trough of hypotension in an amount exceeding the urinary output resulted in the return of arterial pressure to control levels in each patient. Although an increase in plasma volume was noted in each patient, it was significantly below control levels. The central venous pressure, cardiac output, and state of negative sodium balance following the glucose infusion remained unchanged, but the extracellular fluid volume had re-expanded. It would seem that the changes in arterial pressure either after furosemide or during the glucose infusion were related to changes in extracellular fluid. The fact that a decreased pressor response to norepinephrine following furosemide was associated with a decrease in extracellular fluid and the fact that expansion of extracellular fluid with glucose restored the pressor response to normal further document the importance of the extracellular fluid in the regulation of arterial pressure.