Actually, personally, I found 'Mum' (first from a registrar a few years younger than me) quite touching, in that it acknowledged my still very new status as dd's mother and the importance of that role to her. Mostly, it made the point that she was the patient, the subject of every sentence, I was there in a supporting role, and they were busy.
Mostly, when things were calmer, in daily ward rounds and chats with nurses, no direct address was used and i was talked to as the competent adult I am but, when the doctor on duty, who i hadn't seen before, was trying to insert a new cannula without success at 3am, while I held her, I really didn't mind being addressed as Mum, or that he said 'sorry baby' rather than focusing on getting our names right.
I'd feel totally differently if a HCP at a regular appointment did it, as they have time for basic introductions and pleasantries.