Good morning Daffy!
After his initial surgeries, my son's septum again collapsed. The surgeons needed to determine how much damage occured behind his nose. This same procedure was used. For us, I realise, it was quite different circumstances. I think this time, the process took many hours, as they were doing reconstructive work and having to peel back part of the nose/face. But my son told me that of all the things he went through following his assault, the idea of a tube going into his throat didn't bother him at all.
http://bigworldsmallboat.blogspot.com/search?q =when+violence+touches+your+own
I think, for your circumstances, the reason they want you under a general is that they will want to position your head back a bit, rather than how it's often done, in a chair. I'm sure it's more for your comfort.
Will you be having this done soon? I shall keep you in my thoughts.
Fr Bill