How do you handle when a dementia patient forgets important facts, and then feels betrayed because they say they didn't know?

Hugemom is right. I deal with the same issues with my dad.

His short term memory is shot. It’s a waste of time to play “Don’t you remember so & so Dad?” He doesn’t.  There’s no use in trying to get his buy in for anything around the house, doc appointment etc. We just make plans, then fib, divert, whatever it takes to keep him calm and get things done. My mom’s not very good at it. I should get the Oscar.

So far we’re pretty lucky with Dad as he’s still a pretty sweet old guy. For example, he would never agree to get the carpet cleaned but when the guy showed up, “An old buddy of mine,” Dad was just fine with it.  I told him it was free.  My buddy had some left over soap.  He’ll go for most anything if he thinks it’s covered by insurance or free so I run that story quite a bit.

Tell you’re mom whatever she wants to hear and don’t nuts trying to accommodate the dementia.

Yes, a lot of us have been there. I was before Mom passed in November. I learned you can’t reason with dementia patients. By the time you’ve finished with the explanation or reminder that “we already explained this”,they’ve forgotten where you started. This is where the “dance lessons”come in. You need to tap dance around the truth. Tell Mom you’re having the house painted and it’s not done yet. Or having it fixed up some other way. I constantly fibbed to my mom. Trying to explain, ad infinitum to her the truth of the way things were was frustrating for me and upsetting for her.

I learned this from an aide at her facility. She was a blessing!

When my LO was in that stage, I tried to always act like she was in charge and telling me what to do. I'd say, what a good idea it was for her to stay at AL to get her health back. And how smart it was to do this or that. I gave her credit. She just smiled. And for awhile, I would take a treat and balloon with me when I visited. If she was upset, I'd always say that I had already resolved it, with a phone call and I was there to celebrate the resolution. She would be so grateful and we'd share some cookies and soda.

I try to do what Hugemom did. My mom is somewhere in the middle of the stages. She forgets daddy died and goes looking for him. Fibblets do not always work for her. She gets mad because she says nobody told her he died and when is the funeral. But a little bit later she may remember. She also calls and says she can't find her parents phone number in the book. Then we go through it all again. Mama, if your 84 then how old would your mom be? Mostly nothing works the same each time. It happens to everyone over and over. We just muddle through with calming meds and love. Eventually this phase will be over. It is SO HARD!

To tell them that a person died is too hard. They feel the pain over and over. I agree divert. Now my aunt will ask me "Did someone in the family die?" I'll just say, "No, not recently, do you want me to let the dog out?" and go on about my business..
And then I'll hear her telling someone else about the person who died and you will think, she knew it all along! Then later, you can tell that she's forgotten again. And so it goes.

I was lucky, I got my Alzheimer friend through hospital into rehab and from there straight into a home with a notary calling in some favours. But her home stayed empty and locked for many months because I was afraid she might get out of the home, walk up the road to the corner, turn right, turn right again and find herself in her old street. Luckily security was good, so that never happened. Finally the notary (in charge of her finances) suggested the flat should be rented out to get some income to pay the charges. I did this secretly, not telling anybody except the neighbours. My friend still doesn't know, and her "boyfriend" never asked.
Silence and avoiding the subject are the best strategies. But never explain.

I call it 'side-stepping my answers' but it's the same as dancing or fiblets - I love that, never thought to call them fiblets.

When my dad would ask a question that I didn't want to lie, I would side-step it and get him onto another track. Sometimes you have to answer and I would do 'half-truths' - it has to be something you can remember because you never know when they will have a more lucid moment.

Hopefully you will feel better just knowing it happens to all caregivers eventually.

I also agree with komentaightor - sometimes the less said, the easier on everyone.

The people before me have offered great advice, so I won't offer more. I will tell you I understand how frustrating that is. Correcting their incorrect memories will just make them angry or suspicious of you. My grandma used to tell me the way she remembered things, (not remembering events 5yrs before, and thinking they were 25yrs old etc) correcting her literally made her so paranoid of me she started telling horrible stories about me. Most of my family members still believe those stories, and I find myself frantically trying to prove the truth. Moral of the story, follow the above advice, and don't correct her.

My mom does not have dementia but when her memory started failing I began a notebook to communicate back and forth. A daily running commentary that she could read back on what happened. On important subjects, I had her sign the bottom of the page or answer in writing. It helped me when I needed to go back in time for a fact or figure as well as provide proof to any sibling that may be expressing doubt.

Excellent responses here. The only point I'd add is to possibly have some responses 'lined up' so you won't be caught (as) off-guard. While fiblets is cute phrasing [reminds me of 'switch and bait in a car lot' or advertising], it is really YOU (US) learning how to (1) cope and (2) interact-deal with a person with dementia - to support them (1) to be as comfortable and 'un-triggered' as possible; (2) to support their maintaining an even mood; and (3) support the carer to not be triggered. I don't know if you see the insurance ads on tv now - a situation is occurring and someone responds (answers) with a totally unrelated fact about how great this insurance is - and the subject is shifted. We/ you/ us are learning to do the same thing. It is a skill that we learn as we do so stumbling along the way is part of the process. The saving grace is that usually whatever 'we' say is forgotten and we have another opportunity next time.