If health care proxy is invoked due to dementia while parent is in the hospital, does this stay active indefinitely?

If your mom won't sign a permanent form on her own, I'd say you have a problem. If she already signed one, then you have it. Unless she formally revokes it in writing, the ball's still in your court. Don't listen to me, though, I'm not an attorney. ;)

When my mom was in hospital she was diagnosed with dementia but the real problem was not being fed. When she was at home with me she would be fine. VEGGIES ARE IMPORTANT TO THE PROPER FUNCTIONING OF THE BRAIN!!! I can't stress that enough! In addition, a nurse advised me to have a doctor remove the finding from her records WHILE during a stay in the hospital. Otherwise you must appear before a judge, with attorney and two independent witnesses to remove it later.

Just hang onto it in case you need it again. You probably will.

Ask a social worker to determine if your parent is truly able to make all her decisions for her own care. That way her health and safety is confirmed.