out on one's feet

Such schedules frequently leave them ragged and unrested. "How good is it for a patient to be treated by an intern who is almost out on his feet?" she asked.

"Well sir, that girl was simply out on her feet. It wasn't from drinking, either. I'm something of a hypnotist myself and I quickly realized that she was in a real hypnotic trance, brought on by Puffy's staring into her eyes."