To obtund is to dull or lessen the pain of something. If your senses have been obtunded, you are probably pretty out of it.
The verb obtund is rare today, used mainly in medical terminology, and usually in the form of the adjective obtunded. It's been around since about 1400, meaning "to make dull" or "to make less sensitive," and rooted in the Latin obtundere, "to blunt or weaken," or literally "to beat against." It's a close relative of obtuse, which means "dull or blunted," but usually describes a person who is extremely insensitive to others' feelings.