Feet Dry mentions about pan-pan medical being used in the nautical world....
I believe under JAA the term is used, but only to a medical transport flight pursuant to the 1949 Geneva convention.
In my understanding this is for when you have a sick bod onboard from start to finish, or if you are presumably SAR with wounded on board or carrying live organs etc. Maybe someone from ATC can confirm this, I believe the idea is that they give you priority routing but know you obviously are going to be there in advance so in some ways can "plan" for you. I don't think it is phraseology that would be used in the situation described above, again if someone from ATC side can maybe clear this up.
cheers
Bigair