Fluid types and their utility at home is one of the great untapped skill sets for furthering the health of cats going through issues. I am sure to discuss more of this in the future!
Basically, you have NaCl, Lactated ringers, normosol, plasmalyte, and dextrose solutions.
These types of fluids are mostly different in their sodium concentrations, although potassium, calcium and the other electrolytes will change as well. The most common you could be sent home with to use is lactated ringers. That is a type of fluid that is less salty that saline. Which type of fluids that you use depends on how dehydrated my patient is, if they are suffering from acidosis, other electrolyte imbalances .
So it’s a case by case sort of thing based on what medical problem you are treating.
I would surmise that most cats would get sent home with lactated ringers (especially for kidney issues).
There are alternatives that are worth discussing too!