I would keep it to myself. In order to be able to do your job, you need to be able to tell casualties that anything they tell you will be confidential. If you break this confidentiality, you can no longer truthfully do this, and you have broken an important trust that you need in order to do your job properly. Unless it is going to endanger you/your crewmate/hospital staff/patients, you should keep it confidential - for the sake of all future casualties. As I understand it, legally, you are only entitled to break this confidentiality in order to protect your own, or other people's safety, and for no other reason.