Some anesthetics work because they keep you from remembering the pain. When you die, you have no memory of anything including dying.

Do we have first-hand testimony from the dead? 

In all likelihood, our biological expiration is also the cessation of all feeling and consciousness.

Some may find it pleasant to believe in an afterlife, that’s fine; they would never have to regret if they are mistaken. This post was edited by Don Barzini at January 24, 2018 7:16 AM MST

It doesn't prevent you from remembering. It prevents you from forming memories of it in the first place. Your brain still reacts to the pain at the time unless you're given a medicine to deal with the pain as well. When you die, if it is a painful process, you'll feel it. If, by chance, you're revived after, you'll still remember it unless you were sedated for your death. 

"there is hope for whoever is among the living, because a live dog is better than a dead lion. For the living know that they will die, but the dead know nothing at all, nor do they have any more reward, because all memory of them is forgotten. 
Whatever your hand finds to do, do with all your might, for there is no work nor planning nor knowledge nor wisdom in the Grave, where you are going." (Ecclesiastes 9:4,5,10)

In this case, a + b ≠ ab because the premises are flawed.

I agree with JA's answer.