Pedialyte is high in eloctrolytes, which essentially are sodium. My thought process is that sodium does dehydrate, thus in an animal with loose stools, it isn't helping as much as one would think. However, if it is the ONLY thing you can get it to take, it is better than nothing. When kids are sick, they perspire (fever), sweating out both fluid and sodium, pedialyte replaces both, by including sodium in the mix. (If you think about when you are working hard, upper lip sometimes perspires, tastes salty!) So, being truly dehydrated by those standards, means having lost salt and water mass, not one or the other. Of course, my train of thought could be way off base, but that is my thinking.
As for lactated ringers, those are those bags of fluid you see in hospitals that have an iv drip going, they are used in animals as well, given subcutaneously to replace lost fluids. Clearly, in a relatively active pet, an IV drip is nearly impossible, but you can also draw it into a syringe and inject XX amount directly under the skin. Some (many) people aren't comfortable with needles, but it is the first thing I turn to with sick wildlife, and is often just the thing needed to help perk them back up. It has helped a couple of my squirrels, and saved one of my raccoons from death. Ask your mentor about it, if it is something you are comfortable with. It is a quick way to replace lost fluids, and while they feel a "bug bite" when the needle is sticking them, it seems to work quite well in my experience. Sorry the two posts are so long, some days I don't have much to say, other days you can't shut me up!
Joker
PS. Squirrel-rehab.org seems to recommend pedialyte, so going to check out what they have to say, could be I am wrong in my thinking? Link below!

Squirrel Rehab