This is really interesting. And yes, I am one of those who is quite resistent to many anesthetics. When I was having my babies, nothing worked very well, and when I put my back out several years ago and ended up in the hospital, the only thing that helped the pain was morphine.
I gotta tell you though, I sure loved that morphine! I remember thinking how wonderful it would be to float through the rest of my life feeling like I did while jacked up on the stuff. Scary!