Critical Condition (movie, 1987)

Eddie is a con artist. But this time he's framed and comes before a judge. By claiming insanity, he hopes to get off the hook. He manages to end up in a hospital for a mental examination. That night, a storm breaks out over New York, and the electricity to the hospital is broken. In the ensuing chaos that follows, Eddie is taken for a doctor. Suddenly he is in charge of a whole hospital!