A clinical investigation of nocturnal polyuria in patients with nocturia: a diurnal variation in arginine vasopressin secretion and its relevance to mean blood pressure.

PURPOSE: Nocturia is a common lower urinary condition in the elderly population and nocturnal polyuria is recognized as a major factor responsible for nocturia. A functional change in osmotic or nonosmotic control regarding the water-salt balance with aging may contribute to nocturnal polyuria. This study evaluated plasma arginine vasopressin secretion function in symptomatic patients with nocturnal polyuria and the impact of mean blood pressure on nocturnal polyuria.
MATERIALS AND METHODS: A total of 29 patients who had nocturnal polyuria with 3 or more voids nightly and were screened with a 24-hour voiding diary were evaluated for their diurnal rhythm of arginine vasopressin secretion and osmotic response during a 5% hypertonic saline infusion test. Moreover, the relationships between the severity of nocturnal polyuria, ie the nocturnal polyuria index, or mean voided volume and mean blood pressure were assessed.
RESULTS: Decreased nocturnal baseline arginine vasopressin according to plasma osmolality was found in 11 patients (38%) and the lack of a diurnal rhythm for arginine vasopressin secretion was observed in high proportion. A positive correlation between plasma arginine vasopressin and plasma osmolality was described with a linear regression line, expressed as arginine vasopressin = 0.27 (plasma osmolality - 285), resulting in a 2 to 3 mmol/l upward shift in the threshold of overall plasma arginine vasopressin secretion, although various osmotic sensitivities in arginine vasopressin secretion were observed in individuals. Mean voided volume increased during the night more than during the day (p <0.0001). A significant positive correlation of mean blood pressure with the mean daytime-to-nighttime single voided volume ratio and the nocturnal polyuria index was found (p = 0.0343 and 0.0109, respectively).
CONCLUSIONS: An abnormal diurnal variation in arginine vasopressin secretion is highly prevalent in nocturnal polyuria. Moreover, it is relevant to mean blood pressure or sympathetic tone, such that the effects of nonosmotic control seem clinically implicated. Particular emphasis has been applied to the importance of considering comprehensive assessments not only of arginine vasopressin secretion function, but also of the possible underlying cardiovascular condition or hypertension in the treatment modality of nocturnal polyuria.