SALT SUPPLEMENT INCREASES PLASMA-VOLUME AND ORTHOSTATIC TOLERANCE IN PATIENTS WITH UNEXPLAINED SYNCOPE

Objective-To determine whether in patients presenting with posturally related syncope administration of salt increases plasma volume and imp roves orthostatic tolerance. Patients with poor tolerance of orthostat ic stress tend to have lower than average plasma and blood volumes. De sign-A double blind placebo controlled study in 20 patients and an ope n study in 11 of the effects of giving 120 mmol/day of sodium chloride . Patients-31 patients presenting with episodes of syncope who had no apparent cardiac or neurological disease. Plasma volume was determined by Evans blue dye dilution, orthostatic tolerance by time to presynco pe in a test of combined head-up tilt and lower body suction, and baro receptor sensitivity by the effect of neck suction on pulse interval. Results-8 weeks after treatment, 15 (70%) of the 21 patients given sal t and three (30%) of the placebo group showed increases in plasma and blood volumes and in orthostatic tolerance, and decreases in barorecep tor sensitivity. Improvement was related to initial salt excretion in that patients who responded to salt had a daily excretion below 170 mm ol. The patients in the placebo group who improved also showed increas es in salt excretion. Conclusions-In patients with unexplained syncope who had a relatively low salt intake administration of salt increased plasma volume and orthostatic tolerance, and in the absence of contra indications, salt is suggested as a first line of treatment.