Sooner or later, if you are taking care of a person with a long term terminal illness, which dementia is, you are going to be faced with end of life decisions. I suggest you take a good look at those choices as early as possible so you make them long before you need to make them. I suggest you read this book, think carefully about it, and decide what you are going to do so when the phone call comes asking you about these things, you already have the answer that you made when you had time to think it through.
In fact, maybe everyone needs to read this book and think it through early.
The book is HARD CHOICES FOR LOVING PEOPLE by Hank Dunn. You can read the book for free here
Or order a single hard copy from them (the publishers) or from Amazon.com. If you are an organization, you can order multiple copies on a sliding price scale and the publisher will even print your organization's name on the back cover.
Hank Dunn was a hospice chaplain and he wrote the book both from the point of view of medical decisions but also from an ethical point of view. They are hard choices because they are the choices between life and death, and about letting someone go when they time comes. It clearly explains when you do certain things, including hydration and feeding tubes, and when you don't. It clearly explains when you are actually hurting the dying person when you would take it for granted that you are being kind. And armed with the truth that doctors don't realize you don't already have and rarely explain well during crisis, you can make the right choices for you.
The author does not take it for granted that he knows what the right choices for you and for that particular patient at that particular time are. He gives you the information so you can make them for yourself.