I do not have a cat on subcutaneous fluids but I wanted to respond as I have come to believe that cats should not be fed dry food.

Here are some links on the subject, with the top one being the best, I think. It talks about prescription food as well.

http://www.catinfo.org/

http://www.littlebigcat.com/health/why-cats-need-canned-food-2/

http://www.littlebigcat.com/nutrition/why-dry-food-is-bad-for-cats-and-dogs/

There are also other articles at www.littlebigcat.com

My cat had a urinary blockage while eating dry food and was prescribed dry prescription food after that. Luckily I found the website www.catinfo.org and switched him to canned non-prescription food. He has being doing great since and has NOT had a repeat blockage, even though they are common. I credit the wet food and switched my female cat over as well.

When I had my sub-Q cat I fed him canned. Though I have fed my cats dry food when they are younger, I've typically switched to canned when they get to their geriatric years for a variety of reasons depending on the particular cat.

In spite of all I've read about how bad dry food is supposed to be, I've had four cats who have lived long, healthy lives eating it and three healthy cats who are eating it now.

My cat has been on subqs since Dec 2008. He eats mainly dry rx food. The most important type of food to give your cat is one he will EAT. Mine likes dry, so-so be it, He's doing well.