For simple rehydration, Dextrose, Ringers lactate, and buffered saline in that order is what i have had recommended to me before, the company I rep for also sells a mixed solution that contains electrolites and a buffering ingredient to offset the acidosis problem for scouring animals.
Best to use a large bore needle, and go subQ. The reason is that you can actually drown an animal with too much solution straight IV, fills the heart and lungs with fluids. SubQ is a bit slower, just take it slow as well, or you will have a localized adema problem. Usually most Iv drip sets are set up for 60d per minute, and of course you can slow that down, if in doubt I would. As far as adminitering meds though the IV set, I would be cautious of that, as a "IV push or bolus" type of medication infusion may react to the fluids and gum up the works, and also depending on the type of meds, a huge amount thrust all at once may not be very good for the animal itself. This is why so many drugs are injected into the muscle, it means a slower and sustained release.
A good way to see if you have proper rehydration is to look for bright and full eyes,pull the eyelid up or pull the skin up and if it drops back into place immeditely instead ofstaying pinched or drops slowly , you are in usually good shape. Check the gums, if they are white,not pink, it may be shocky, and it may help to not only keep it warm, but add a bit of dexi to the meds as well. BUT also keep in mind that large or prolonged doses of dex. with often lead to rebound effects such as pnuemonia in a few days.
Good luck! :cboy: