Renal Function and Sodium Metabolism in Idiopathic Orthostatic Hypotension

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Abstract
PATIENTS with idiopathic orthostatic hypotension demonstrate various hemodynamic abnormalities in response to standing. Reflex peripheral vasoconstriction fails to occur normally,1 venous return to the heart and cardiac output are low,1 2 3 and the flow of blood to brain, liver and kidneys is decreased.4 The decrease in renal blood flow results in a diminished glomerular filtration rate5 , 6 and occasionally in urea retention.4 This decrease in glomerular filtration rate may account for the diminished urinary sodium excretions noted in these patients when they stand5 , 7; however, the possibility that changes in sodium excretion are due to alterations in the tubular reabsorption of sodium . . .