Efficacy of high sodium intake in a boy with instantaneous orthostatic hypotension.

We report the case of a 14-year-old boy with instantaneous orthostatic hypotension (INOH) with symptoms of orthostatic intolerance. We investigated the effect of high sodium intake on hemodynamics and circulatory responses to orthostatic stress using Portapres. Moreover, a multifrequency bioelectrical impedance method was used to confirm increased plasma volume. Although we began treatment with an alpha-adrenoceptor agonist after his admission into our hospital, the effect was not sufficient. We, therefore, began a regimen of high sodium intake (NaCl 3 g two times a day per os in addition to regular diet, NaCl 5-6 g /day) to increase plasma volume. As a result, 48 hours after sodium intake, orthostatic tolerance was markedly improved with a concomitant increase in blood pressure in the orthostatic test. By measuring the patient's body water before and after the high sodium intake, we were able to document the increase in plasma volume. We conclude that high sodium intake is an effective treatment for orthostatic hypotension in combination with vasoactive drugs.