My experience may be helpful. I had an episode of orthostatic hypotension and wound up in the ER. After some time, my doctors feel it was from dehydration. Then I began having early morning episodes of very low BP (faint, dizzy) that weren't resolved after eating and drinking (I tend to low BP, but it always goes to normal with breakfast). My cardiologist told me that fluids were going 'right though' me because of mineral deficiencies [for medical reasons, I need to eat a very calorie restricted diet, and the body gets its minerals from food mainly, thus my deficienty] and that's why I remained dehydrated in spite of drinking fluits.
He said that the best solution was to drink a sports drink to get my electrolytes in balance. My primary doctor suggested Pedialyte as the best source.
I haven't had a problem since. I only drink the Pedialyte if I'm feeling light headed in the morning, and that resolves the problem immediately. But my episodes have been fewer and fewer. I will sometimes drink it after exercising, too.