I think Wiki has that slightly wrong.
Red haired women have the highest pain threshholds of all humans, that's been scientifically proven. They also respond better to lower levels of pain medication for pain management than others.
As for the anesthesia, not sure that's so true either. I'm a redhead and have had 4 major back surgeries in the last 15 years. I can tell you that one of the anesthesiologists that put me under I literally scared the hell out of, as he put me so far under they had a hell of a time bringing me back. From what I was told, I damn' near slipped into a coma. I had to make it a point to tell the three that followed him that I go under easy, but tend to not come back quite so easy. The three of them were able to 'adjust' well enough so I was able to wake up afterwards much easier than the first surgery.
I can also tell you that I needed minimum pain management after a herniated disc repair, then a collapsed vertebrae (walked with that for 9 months), a spinal fusion then a bone spur removal from the surgery site just two years ago. Most of my pain management consisted of nothing more than some nerve pain meds (lyrica) and tylenol for a week or so following the first two surgeries. Two weeks after my spinal fusion at L5-S1, I was walking up to two miles a day on my treadmill. Not bragging, that's just who we're wired I suppose.
THAT's impressive.