Plugging the leak Benefits of the vasopressin-2 agonist, desmopressin in autonomic failure.

Nocturnal polyuria is a common symptom in autonomic failure. In patients with urinary bladder involvement nocturia can be troublesome and considerably add to their disabilities. Nocturnal diuresis and natriuresis account for overnight weight loss that appears to worsen the extent of, and symptoms resulting from, orthostatic hypotension in the morning. Some patients are considerably incapacitated and find it difficult to function until late morning; even a light breakfast and minimal exertion can substantially worsen symptoms. This partly may be helped by the use of head-up tilt at night. Nocturnal polyuria probably results in redistribution of body fluids, reducing central filling pressure, stroke volume, cardiac output and thus blood pressure. This is consistent with recent studies confirming that orthostatic hypotension is worse in the morning and indicating that there are greater changes in stroke volume and cardiac output on standing in the morning compared to the evening. The reduction in overnight fluid loss presumably reverses this cycle of events, thus reducing morning orthostatic hypotension.