Impaired Arginine-Vasopressin Secretion Associated With Hypoangiotensinemia in Hypernatremic Dehydrated Elderly Patients

Abstract

Nine elderly patients, some with preceding dementia, presented with adipsia, progressive dehydration, impaired consciousness, and hypernatremia following common acute infections without gastrointestinal disturbance. Studies before rehydration revealed inappropriately low plasma arginine-vasopressin (AVP) levels for plasma osmolality, insufficiently concentrated urine, absolutely or relatively low plasma angiotensin II (A-II) concentrations (compared with plasma renin activity and plasma angiotensin I concentrations), and low serum angiotensin I-converting enzyme activities. The plasma AVP concentrations were positively correlated with the plasma A-II concentrations (r = .677) but not with plasma osmolality. The plasma AVP level was raised by an intravenous infusion of A-II in one patient. These findings suggest the following sequence of events: impaired A-II production caused impairment of thirst perception, renal-concentrating capacity, and AVP secretion and contributed to development of hypernatremic dehydration in these elderly patients.

Severe Hypernatremia with Impaired Thirst

“…Their AVP response to orthostasis and their renal tubular response to AVP may be impaired, however [45,46]. In a recent study in elderly patients, some with preceding dementia, the authors postulated that reduced angiotensin II production was causally re lated to impairments of thirst perception and AVP release leading to a negative water balance [105]. These preliminary observations are in agreement with animal studies demonstrating large numbers of angiotensin II receptors in the subfornical organ, a brain structure felt to be the site at which angiotensin II acts to cause drink ing, and increased vasopressin secretion [106,107],…”

Hypernatraemia in the Elderly Patient

“…Other patients manifest both hypodipsia and upward resetting of the osmostat such that the threshold for vasopressin secretion is raised and/or the responsiveness of vaso pressin to changes in plasma osmolality is impaired [7], This has usually been reported in hypothalamic disease, but also occurs in elderly subjects with less well-defined mental and physical impairment [48]. In some of these patients serum angiotensin-converting enzyme concentration is low and reduced angiotensin II production may impair thirst, vasopressin secretion and renal concentrat ing ability [48].…”

“…In some of these patients serum angiotensin-converting enzyme concentration is low and reduced angiotensin II production may impair thirst, vasopressin secretion and renal concentrat ing ability [48].…”