I pray for you as we are going through this with my dad. They have not told us that there was nothing else they can do, however I feel your pain. Please pray pray and pray.
I have been a nurse in a nursing home for 17 years. When our patients are very ill as your mother is, they are, of course, sent to the hospital. So, I cant say either way that I've seen the type of "miracle" you are looking for. I can tell you I've seen alot of people pull thru against the odds. The best advice I think I can give you is to look at this from your mother's point. What would she want you to do? If you are not exactly sure what your mother would want, then what would you want your kids to do if this way you? If you make decisions based on what you believe is best for your mother, then the decision wll not be a wrong one.