Dehydration

Brad Edwards said:

How do you know when dehydration has progressed to the
point where the body is unable to rehydrate through oral
fluids and requires IV fluids?

When efforts to do so aren't sufficient.

Skin turgor is an easy sign anyone can check. Pinch up the
skin on the back of the hand. Does it fall quickly back into
place? (<2 seconds) Or does it "linger" and smooth out only
very slowly? (> 4-5 seconds) If it's the latter, they're
getting seriously dehydrated. Try it on yourself and then
try it on someone who's dehydrated. You'll see an obvious
difference.

Quoted message said:

Besides drinking water and gatorade, are there any other
practical home methods for treating dehydration?

Check the pharmacy for products intended for this (I
believe one brand name is Pedialyte). But mainly, they've
got to like it enough to consume enough of it and be able
to hold it down.

This is really something the person's doctor or nurses
should be advising you on. Sounds like they could use some
home nursing care.