One of my cats spent Sunday afternoon in the kitty emergency room. She has bladder stones, but that might be incidental and not what was causing her to lose her balance, throw up and breathe fast. This hasn't been a fun week.
Ugh. I feel your pain. Did they do a blood panel? If her electrolytes are off kilter, then you should have her adrenal glands checked. I had to put one of my cats down they other day. I haven't been this sad in a long time. He was my favorite cat. Good luck. 
I don't think they ran blood work. The emergency vet got her respiratory rate back to normal, and she seemed fine by the time we got home. They did take X-rays to see if anything was wrong with her legs or anything to account for the wobbly gait, and that's where they found the bladder stones. We saw our regular vet today, and she recommended removing the bladder stones. She was hesitant to say they were causing her to be wobbly and throw up, but it's possible if they were causing her pain. Even if not, the bladder stones aren't doing her any good, so we're going for surgery next week. I want to say this to someone: this is expensive. I can afford it; that isn't what I mean. But it's still a lot of money. But I love my little girl, and as long as the diagnosis is hopeful, I'll do what I can to help her. I'm so sorry about your little guy. Pets work their way into our lives in such a meaningful way.
No joke. We ended up in kitty ER mere weeks after we got ours. $350 for some saline under the skin and, antibiotics and pain relief. Would have been more if we left him with them overnight by an order of ridiculous. He seemed fine at the adoption place but came to us with a virus nonetheless. Doubled down with a bacterial infection days later. We have accident/emergency insurance for him now, and he's on supplements to help prevent recurrences of the virus, but there's no hope of illness coverage since his record has evidence that he had been sick before we got him covered.I want to say this to someone: this is expensive. I can afford it; that isn't what I mean. But it's still a lot of money.
It must be tough to be in the ER so soon after adopting him. My little girl has been home for over two years, and we've gotten close in that time. It's tough to put down so much money, but it's really tough to see her struggling, too. I was in for $500 at the emergency vet (mostly X-rays, which did prove helpful) and will be over $800 next week to have the bladder stones removed. It's probably for the best, but last week I also booked a vacation. It's good for me to get away, but the flight, two vets and hotels I've yet to book will make July expensive. But that's why I work (not to imply I dislike my job). I hope whining in pubski is ok.
We were angry. He started sneezing like 3 days after we got him, and visibly sick by the end of that week, then I got a call out of the blue from the foster or shelter saying another cat he was near was being syringe fed because of a virus. You'd think they'd have picked up that the cat was sick before we we adopted the kitten. So there I am, not having had a kitten since I was a kitten toddler, figuring out from the internet whether he was in danger, pureeing up canned kitten food with extra water to try feed him with a syringe and trying to convince husband to drive us to the emergency vet.