ELECTROLYTE AND WATER EXCRETIONS AND RENAL HEMO-DYNAMICS DURING INDUCED CONGESTION OF THE SUPERIOR AND INFERIOR VENA CAVA OF MAN 12

Abstract

Elevated vena caval pressures, ranging from 100 to 250 mm. saline soln., were produced for periods of 30 min. by the inflation of a balloon in the inferior vena cava above the renal veins in 16 subjects, in the inferior vena cava below the renal veins in 13, and in the superior vena cava in 12. During the venous congestion of each of the 3 areas essentially similar changes occurred in water and electrolyte excretions, renal hemodynamics, and arterial blood pressures. The urinary excretions of Na and chloride, and less consistently of K and water, decreased. Urinary electrolyte concns. tended to remain uncnanged, and the reduced electrolyte excretions were usually due to the reduced water excretion. Occasionally water excretions decreased little or not at all, yet electrolyte concn. fell decidedly. Renal plasma flow and glomerular filtration rate usually decreased by 15-25% at the onset of the venous congestion and concomitantly with the reduction in water and electrolyte excretions. As venous congestion was maintained, both renal hemodynamic functions improved and were returning toward control values while water and electrolyte excretions remained at their low levels or decreased further. Filtration fraction did not change. Systemic arterial pressure changed little; systolic pressure and pulse pressure fell slightly (5-10 mm. Hg), while diastolic pressure and mean pressure remained essentially unchanged. Heart rate and the ecg. remained unaltered. Arterial hematocrit and plasma protein concn. did not change. Following release of inferior vena caval congestion, both including and excluding the kidneys, water, and electrolyte excretions, renal plasma flow and glomerular filtration rate returned to, or well toward, control levels, the renal hemodynamic functions promptly, the urinary excretions within 30 min. Following release of superior vena caval congestion, water and electrolyte excretions returned toward control levels slowly, or not at all, and were still reduced 30 min. after release of the congestion. Renal plasma flow and glomerular filtration rate, on the other hand, returned promptly to control values. These observations indicate that acute congestion of a sizable segment of the venous system induces a decreased urinary excretion of water and electrolytes. The mechanisms responsible for this effect remain to be detd.