My vet used to tell me to treat the cat not the numbers. I’m not talking the quantity of fluids of but quality of life.
In other words, try to give it a little while with the fluids, see how he does and how his numbers look on the recheck blood work. In the meantime, if he’s feeling better on the fluids, eating, peeing/pooping and doing his normal stuff, try not to worry about them.
It’s easier said than done but I’ve learned that how they act and feel is way more important than blood work and tests.
None of mine are good travelers or vet goers either. We do have two mobile vet practices here but my work schedule has made getting appointments with them almost impossible for now.
Eta - https://www.felinecrf.org/
I found this website so helpful. Two of mine now have the early stages of kidney disease and I’m revisiting it often.