I am so sorry that you had a such a difficult experience in the ER with your loved one's sundowning. It is terribly frustrating for all that are trying to do what is necessary to make the patient feel better including you and your other sister. And no picnic for the patient either. In my experience there is absolutely no way to convince the person with the sundowning that what they are experiencing is not real to them. They know when they feel pain (passing kidney stones is often compared to the pain of childbirth) and when a situation makes them fearful, anxious and even terrified, the natural response for any of us is to flee the situation.
I agree with the previous post about going to an urgent care clinic if at all possible. They are more likely to be less chaotic and possibly have shorter wait times because they don't have to deal with serious trauma, heart attacks and other life threatening problems. Taking her in the morning might allow you to avoid the hours where sundowning could be a problem. Having a mild sedative at home that you could give with her other morning pills before the visit would probably help some. Also, as you have been doing when checking in, forewarning the staff of her dementia, the need for a quiet atmosphere, minimal contact with staff (strangers who touch her) and her low tolerance for waiting. I agree that speaking with the hospital's Patient Care Advocate is a good idea. I personally would not wait for a second incident. This is the person who can investigate what happened from both sides. It will bring this problem and the staff's response to light. If it were me, I would take pictures of the bruises you feel are from that encounter so you can show the Patient Care Advocate as well as any notes from the results of the x-ray that you said you would be getting from the urgent care clinic. The Advocate, with your input and that of the ER staff, may make changes in or create a new policy for dealing with patients who present with sundowning or psychosis ( break from reality) which happens even without sundowning in older patients who are abruptly take out of their familiar environment or have had anesthesia and wake up surrounded by strangers in a strange place. My husband, before he was diagnosed with dementia had a psychotic episode after each of the two times he had back surgery. He thought he was in our house. I could not convince him that he was in the hospital. He wanted to and succeeded in pulling out his IV and taking off his monitors. The way we managed this was to have either my daughter or myself with my husband 24/7. That way he could at least see familiar faces. I would also insist that you be permitted to have more than one person with your LO to help when she is taken in the back to a room. Also, whenever I have to take him to a doctor's appointment, imaging center, emergency room, chemo appointment, I take my "go bag". This is a backpack that is filled with tissues (for his constant runny nose) his diabetic supplies, snacks for both of us, water, a book for me to read, a change of clothes and disposable underpants( he is incontinent) and anything else that I think would be helpful to either of us. For your sister it may be a small favorite object or some photos of loved ones that you may be able to distract her with while waiting. However, if I was passing a kidney stone there is nothing that would distract me from the pain short of dose of morphine or fentanyl.
I also carry in my purse copies of a form that has all the information the doctor, nurses, admitting clerk would need to know. This saves lots of time when they are trying to get a history of the patient, your sister's would state that she has a history of kidney stones and of course her dementia. This can speed things up considerably and explain the severity of her pain. Also current medications, previous significant surgeries/procedures. One ER physician that saw my late father said " this form just saved me a good 20 minutes" If you are interested I can email you a copy of this form. I hope that all the suggestions made by everyone on this thread are helpful. This is really a tough thing to deal with. You are in my prayers.