I have DIRECT experience with this.
I had them. They denied my anesthesia completely for my surgery. I broke my leg in five places as well as my thumb and needed a plate in my hand as well as a plate in my lower leg and a rod in my bone. They must have though, "Oh, the patient should be awake and aware throughout this procedure." I fought it for months and gave up. They never covered it. I feel bad for the anesthesiologist. He deserved to get paid for his services. This was over a decade ago so I no longer owe it, never paid.
The insurance suits get what they deserve.