How rare is it to feel pain under anesthesia?

Understanding Awareness Under General Anesthesia

While it is extremely uncommon, there are instances where individuals may find themselves partially conscious during general anesthesia. Estimates suggest that approximately 1 to 2 individuals per every 1,000 may encounter unintended awareness while undergoing surgical procedures. The occurrence of pain during such episodes is even more infrequent, but it is possible. In fact, this happens so seldom that it is not a major concern.