Quote Originally Posted by Cumulus View Post
Well, my question is:
What if I were a new patient that is abs. strange to him and vice versa? Господин Живаго? (No "Доктор..." pls )
Well, in this case, when addressing directly to him, usually it's just "доктор" (no name attached).
If you know him well (he's your attending doctor) you say Сергей Владимирович.
And if he's your good fellow and you are about same age you can say Сергей or Серёжа

Господин\Госпожа can be heard in media, political debates, official papers etc, but common people rarely use it, mostly with irony\sarcasm.