This information is related to engagement of surgeon(s) in addition to an original doctor in-charge.  It is written because of changing society norms on consent and responsibility. There is no need to imagine specific incidents as trigger. It applies more directly to operations but the concept may be generalized to any medical intervention.
When an additional co-surgeon B is engaged by the original surgeon in-charge Dr A, it is generally good practice for A to introduce B professionally and explicitly to his client.  The degree of necessity probably parallels the responsibility and decision making capacity of B in the treatment.  If B is serving completely as a passive assistant, the need of formal introduction is less compelling than another situation when B is a supervisor, principal operator or decision maker. When problems or complications happen, it is way easier for either doctor to clarify misunderstanding, if B has a chance beforehand to meet the client and provide explanation. In addition, Dr A needs to take heightened awareness and care in the original explanation when more than one surgeon is involved.
It is already our norm that the second surgeon signs the consent form.  Therefore the consent process formally engages the second doctor.  It is only appropriate that each doctor signing the consent also has a chance to explain directly to the client, so as to discharge duties properly.  Nurses have been instructed that it is necessary to introduce a second surgeon to the client prior to surgery, the latest at time-out if the patient is not under effect of drugs.  Please do not feel offended, and try the best to help them, if our nurses are not very efficient in handling this aspect.  It is logically better to introduce the second doctor prior to transport to operating theater, when the client does not feel compelled.
Colleagues are welcome to talk to me if they want to practice how best to handle related communication.  In case of need, a doctor may call me there and then in clinic to rectify acute communication distress.  The explanation is usually straightforward.