5 days ago my medium haired male tabby cat got very sick. He vomited a lot all in one time. There was some h

5 days ago my medium haired male tabby cat got very sick. He vomited a lot all in one time. There was some hair, but it was food as well. I had him on Hill's SD formula because he'd had crystals in his urethra about 6 months ago and almost died. He now is very sick and lethargic. I took him to the vet first thing and he put him on an IV to hydrate him and said he threw up another hairball while he was there, but that he thought he'd be fine. Said his throat was swollen and very sore. Told me to put him on pedialyte - 10 ccs 5X daily - and baby food (chicken) and Catlax, which I noticed had moles in it. I guess it was to boost his energy and then also to make sure that no hair was lodged in his lower intestines. I brush him often, so I don't think that he could get so sick via hair. Also, his brother is just like him and is not sick. And the vet said he looked toxic. His middle eyelid - in the corner of his eyes - was up. He was panting like he was in bad pain that night