[Electrolyte imbalance in the elderly].
Imbalance of water and electrolytes in the elderly was investigated. In the elderly, hyponatremia is the most common electrolyte imbalance disorder and half of the cases with hyponatremia are accompanied by malignancy. It is well known that renal function decreases with ageing, and hyporeninemic hypoaldosteronism, relative AVP unresponsiveness and high level of plasma ANP are observed in the elderly. Therefore, renin-aldosterone system, AVP and ANP as well as renal function of the elderly were studied. AVP response to osmotic stimulus in the elderly increased, indicating that osmostat hypersensitivity existed in the elderly. The response of ANP to hypertonic saline infusion was well preserved. Increase in FENa with decrease in GFR and decreased salt-retaining renal capacity, with low response of the renin-aldosterone system, under low salt intake were observed in the elderly. Therefore, the low response of renin-aldosterone system may be, in part, involved in the pathophysiology. Plasma ANP positively correlated with FENa and the rate of the response of FENa to endogenous ANP was lower in the elderly than in young adults. In addition, the ANP disappearance rate from plasma in the elderly decreased. It was, therefore, suggested that those factors might be, in part, responsible for the increase in plasma ANP level. Accordingly, a high plasma ANP level might be relatively non-contributory to hyponatremia in the elderly. In summary, hyponatremia is the most common disorder of electrolyte imbalance in the elderly.(ABSTRACT TRUNCATED AT 250 WORDS)
Yamada
K
K
Yoshida
S
S
D000368:Aged; D000375:Aging / Q000502:physiology*; D001127:Arginine Vasopressin / Q000502:physiology; D009320:Atrial Natriuretic Factor / Q000502:physiology; D006801:Humans; D012084:Renin-Angiotensin System / Q000502:physiology; D014883:Water-Electrolyte Imbalance / Q000503:physiopathology*
D001127:Arginine Vasopressin; D009320:Atrial Natriuretic Factor