Hello again
@Tilly_123, and I apologize in advance for a long post with a lot of advice you didn't ask for.
My mother (now 75 and middle to later stage Alzheimer's and no short term memory, care home for 3 years) has had two surgical procedures with dementia, one this year for a fracture, and one about five years ago, before her diagnosis but not before her dementia, if that makes sense.
Based on those experiences, here is what I'd recommend.
Speak to the anethesiologist before the procedure and emphasize your mother's mixed dementia and your concerns about anesthesia and its effect. Ask any questions you may have. They often have a terrible bedside manner, so be warned.
The next section is all from my mother's surgery in February, 2017.
I asked and was permitted to accompany my mother into the pre-operative waiting area (which they don't normally allow) because of her dementia. I stayed until she was sedated.
I asked to be present in post-op when they brought my mother out of theatre, but was denied and told they would page me to meet my mother in her room about two hours after the procedure ended. I got a page about five minutes after she went to post-op and told to come immediately as she was agitated and couldn't be calmed by staff. I stayed in the PACU with her until she went back to her room, and they fast-tracked her out of there.
As my mother currently lives in a care home, she was admitted to hospital the day before the procedure for all her pre-operative tests and preparation. The care home would not have been able to manage that, especially the blood work and having her NPO/nil by mouth before the surgery. It was bad enough in hospital.
I made sure to tell every single staff member, nurse, doctor, whomever, with whom we interacted, that my mother has dementia and cannot accurately self report or answer questions. I mostly did this out of her sight and hearing so as not to distress her. I always have a note with that information written on it, that I can hand to whoever is there. Some of the nurses would persist in asking her questions she could not answer. I stood out of her line of sight and nodded yes or no or shrugged, to give them the answers.
She could not be relied on to accurately report her pain, as she would not always be frank with members of staff (some variant of hostess mode), so I always had to make sure she was given her pain meds on schedule.
To keep track of that, and the name of every person I met, I had a hospital notebook and wrote everything down, including the names of the nurses and what shift they were on.
She could not order her own meals in hospital, so I did that for her. Her appetite was not good so I made sure she would have plenty of appealing foods.
She also didn't tolerate anything invasive, including injections (she required a daily injection to prevent blood clots) and the IV, well at all. She frequently removed her IV and they had to replace it many times, and put large dressings over it. She also would remove her leg brace and surgical dressings if not supervised 24/7, was confused by the airflow mattress she was on, and would get out of bed and walk unassisted if I so much as turned my back for more than ten seconds.
I could go on, but you get the idea. My most important piece of advice is to have someone with your mother as much as possible, ideally 24/7. My mother got hospital induced delirium and it was terrible; be on the watch for that. With luck your mother won't need a long hospital stay.
My mother had a very minor surgical procedure for a thyroid issue about five years ago. At the time she was not diagnosed with dementia, but in hindsight, she was early stage with her Alzheimer's and having some memory problems. Her capacity fluctuated. She was also resistant to help at the time, other than transport to appointment, and lived alone.
She was not able, and did not, follow the directions for before or after the surgery. She did not take her medication correctly. She did not take care of the wound correctly. Because of the dementia, she was not able to do those things. In hindsight (of course) I would have done all of this differently. Most importantly, I would have made sure she was supervised 24/7 before and after the surgery, or admitted to hospital for them to do it. She was lucky to escape complications.
I am not trying to upset or scare you, and apologize if that is what I've achieved. I only want you to be aware of some of the issues that a PWD and the family face with a surgical procedure and stay in hospital, and how you are going to cope with what she needs before and after surgery.
I would be happy to answer any questions you have if possible.
There is good info here:
https://www.alzheimers.org.uk/info/20046/help_with_dementia_care/40/hospital_care
Very best wishes and hope all goes well.