awww, I'm so sorry to hear this, Cheri.
I hope he does recover fast. What a shocking thing to happen, I just am speechless. How come they were using Ketamine? Is that usual in veterinary medicine?
I know this is not quite the same situation, but my daughter's cat became extremely ill a few years ago after eating tulip leaves. The tulips were in a vase in my kitchen. She only had one seizure to my knowledge, but was left for a long time after recovery with different sized pupils and also with some syndrome, which is when the third eyelid that cats have to protect their eyes stays covering their eyes. Thankfully she made a good recovery and has never had any problems since then.
I know what's happened to Moonshadow is so much more serious, but I have to hope that he'll make a good recovery and very soon as well.
My thoughts are with you and I'm hoping that your son is ok. I totally understand how stressed he must be feeling. He has always sounded like such a sensitive and gentle soul and my heart goes out to him.