Would you start a vaptan or monitor an asymptomatic patient with reset osmostat and an average sodium of 126 meq/L?

No therapy is required if the patient has hyponatremia due to a reset osmostat, since the patient will regulate the serum sodium concentration around this new baseline level. The key question is whether or not the patient actually has a reset osmostat. A patient with hyponatremia due to a reset osmostat should be able to dilute the urine appropriately below this new baseline sodium level and concentrate the urine appropriately above the new baseline sodium level.

It might work unless their thirst threshold is also reset, in which case tolvaptan would cause only polyuria.