Water drinking in the management of orthostatic intolerance due to orthostatic hypotension, vasovagal syncope and the postural tachycardia syndrome.
Water drinking recently has been shown to raise blood pressure in normal subjects and in patients with autonomic failure who have orthostatic hypotension. However, in normal young subjects, ingestion of approximately 500 ml has no pressor effect; but in older subjects there is an increase in blood pressure. An even greater rise in blood pressure occurs in cases with autonomic failure. The possible mechanisms responsible for the pressor response to water include neural and humoral factors; fluid redistribution also needs to be considered. This review will concentrate on the water pressor response in normal subjects and different groups of patients with autonomic diseases who have orthostatic intolerance, on the mechanisms that could be involved, and on whether this pressor response may be used in the management of orthostatic hypotension, vasovagal syncope and the postural tachycardia syndrome.