However, the occurrence of hypernatremia in this study was
relatively frequent compared with the QUEST study. Hypernatremia
sometimes results in central nervous system disturbance,
and therefore careful observation of serum sodium levels is
essential. We observed that hypernatremia emerged within 3
days in most cases, and frequent measurement of electrolytes
is recommended, especially during the initial phase of tolvaptan
treatment.
Although serum sodium levels must be monitored in all patients
treated with tolvaptan, there is a population that is prone
to be complicated with hypernatremia. In this study, we reported
3 independent predictive factors for the occurrence of hypernatremia
for the first time: serum sodium ≥142.0 mEq/L, starting
dosage of tolvaptan at 15 mg/day, and serum potassium