Swami Thuryanandaji sat through an operation very calmly. The next day when the doctor came to dress the wound, he opened the bandage and started cleaning it,. immediately the Swami shouted in pain. It could just mean it's like a meditative anesthesia. You actually do not feel the pain. yogis can concentrate their mind because we have a limited cognitive bandwidth. If you occupy your mind completely with one thing, your mind will not take in information coming from elsewhere.