I asked the surgeon if I could administer my own anesthetic. They said, ‘Go ahead, knock yourself out.’

Behind the Groan

Permission to Knock Yourself Out

“Knock yourself out” can mean that someone has permission to proceed, but anesthesia is also intended to make a patient unconscious. The surgeon's casual permission therefore describes the literal result at the same time. Keep the setup straightforward and put a slight pause after “They said.” The familiar expression should sound natural before its medical meaning catches up.