IIRC, the usual compound used is Potassium Chloride, not Potassium Acetate.
It’s the Potassium that causes the heart to stop. The anion is not important, afaik.
Also, I think this is administered after the condemned is unconscious.
I just got out of the hospital myself, serious heart attack with a side order of Drowning-on-dry-land Pulmonary Edema in the Cath lab.
I managed to pop open my Femoral vein (not artery) sitting up for lunch in bed. I felt suddenly like I was in a warm bath. I looked under the covers and I could see (easily) a pint of blood and more coming out. I direct pressured it and got it under control. I called out to the ICU nurse when he came past again. "Sorry, I know you're busy, but when you get a minute- I'm bleeding out here".
Apart from that really woozy, bone-chilled feeling you get when you lose too much blood, it was utterly painless. We were laughing about it while he was mopping it up with big clumps of totally-soaked towels. We both shared the same dark sense of humor.
Point being, once you're beyond the pain, it doesn't matter how it happens. You could keep him anesthetized and shoot him to death with BB guns over the span of a couple of weeks. Once I'm under, I don't know and I don't care what they're doing.