Hydration IS a good tool for dysautonomia...to help keep your BP up when standing. However, the IV saline doesn't last long, so has to be repeated frequently...probably the reason most doctors don't order it. If your symptoms improve then he may try it for a short time (multiple infusions).

But you can typically achieve the same by drinking fluids. NOT just plain water---it needs to have other substances in the fluid for better absorption. This is partially why Gatorade and other drinks help with hydration better than just plain water (they also have potassium, sodium, etc). You can get low sugar Gatorade or Powerade.

But I have found the BEST why to hydrate is with 100% natural coconut water (NOT coconut milk or juice). There are numerous articles online about coconut water...even being used in third world countries for emergency transfusions...as it closely resembles the make up of blood plasma. I can certainly confirm that it works for me and has helped with symptoms in a very short period of time (like within 20-30 minutes). Worth trying, if you haven't already.