My 18 year old cat, in great shape for her age and non-symptomatic except vomiting every now and then, was sleeping on my lap today and asking for food. Then all of a sudden she jumped away (or rather fell) as if she had been stung or had a hairball, then she crouched very low (never seen it before) and quickly over the ground away from me and anxiously as if I had done something to her. Then she urinated what seemed uncontrollably; after which she started panting heavily with her mouth open (not good!). She was totally irresponsive to me, never had that before. I tried to reach out to her to take her to the vet immediately but she managed to run away to the neighbours. I saw her sitting there with the same symptoms as I walked towards her but then she went out of reach for me. It is night right now, I couldn't find her because she went to other gardens and there are a lot of bushes. Last I saw is that she jumped a wall. I am very concerned because of these symptoms as they certainly are a medical emergency, I will have to wait until sunrise to look for her but am afraid that I will find out that she has died. I really hate the fact that she was suffering so much. In the meantime I am trying to find out what might have caused these symptoms. As it is so sudden, what I read is that it can be heart failure or poisoning?