Welcome to the forum, kibt
First off, I hope that you are NOT playing amateur-googleing-veterinarian !
You will need a competent feline Veterinarian....I have no idea where in the world you are, so it's difficult to give you specific direction on that front...if there is a cat-only Vet or clinic
accessible to you, that would be a good place to start.
With a competent Vet on board, it is helpful if we, ourselves, have an general understanding of the issue - in this case (apparently) potassium levels in cats - that is something many people can absorb from this plain-language coverage of the topic: All About Potassium (link)
(For now, ignore the fact that this site is focused on kidney disease....the general principles covered there apply to all small cats)
Hope those two suggestions are helpful !