Diuretic pattern in adults with nocturnal polyuria: the possible contribution of blood pressure to the worsening of nocturnal polyuria.

OBJECTIVE

The present study was undertaken to investigate diuresis rate determinants of nocturnal polyuria (NP) in adults.

METHODS

A total of 33 patients aged 50-87 years (mean: 68.6), with nocturnal urine volumes exceeding 10 mL per kg body weight based on records of a frequency-volume chart, were enrolled to evaluate the relationships between diuresis rates and related variables. Multiple regression analyses were conducted to identify diuresis rate determinants, including brain natriuretic peptide. Furthermore, a hypertonic saline infusion test was conducted to examine the arginine vasopressin (AVP) response to plasma osmotic change.

RESULTS

Nocturnal voids correlated negatively with the daytime diuresis rate (P = 0.019). Despite a similar total urine volume per kg body weight (TUV/kgBw), systolic and mean blood pressure (MBP) significantly correlated with the nocturnal diuresis rate positively and the daytime diuresis rate negatively. The MBP, which was selected as a representative variable for blood pressure, was found to be an independent determinant for the nocturnal. The MBP and TUV/kgBw were independent determinants for the daytime diuresis rate on multiple regression analyses. Neither age, AVP, nor brain natriuretic peptide were determinants for them. When divided into two groups using their median nocturnal diuresis rates (0.023 mL/kg/min), there was no difference in the prevalence of stroke and the taking of hypnotics between the groups. Overall, a hypervolemic condition or increased sympathetic nerve activity in NP was suggested using the hypertonic saline infusion test.

CONCLUSIONS

These results indicate that blood pressure might play an important role as a determinant of increasing nocturnal diuresis in NP.