I had surgery on C5/6 in February of 2018.
I did not have a fusion but disk replacements.
The surgery went well and it was done as an out-patient.
I noticed my throat started to itch and swell (but not like you).
It was actually the thing that hangs down the back of your throat (sorry I can't remember what it is called).
I think I might have been allergic to something they used.
I was still able to swallow and the swelling went down in a few days.
I wish I could give you advice other than to take care of yourself and accept any help you can get.