Unimpeded plasma renin increase after intravenous furosemide during saline replacement.

The effect on plasma renin activity of intravenous furosemide combined with saline replacement of the volume depletion was studied in twelve patients with insignificant heart disease. In ten of the patients the investigation was repeated without saline replacement. It was found that saline infusion, reducing or eliminating hemoconcentration, had no significant influence on the marked plasma renin increase. In eight of the patients the combined furosemide-saline study was performed during right-hear catheterization. Decrease in atrial pressures, known to occur within 15 min after furosemide intravenously, was virtually absent with the saline replacement. It is concluded that plasma volume reduction after intravenous furosemide is responsible for decreased filling pressures of the ventricles but not for plasma renin increase.