Dog's hearing loss

I have an 8 year old blind silky terrier that seems to have all but lost his hearing after last night. I took him out last night and a neighbor unexpectedly set off fireworks. The display lasted for about five minutes and he didn't seem scared. I moved him away, but not completely away.

Since this morning he's been unresponsive to calls and sounds. He hasn't been wagging his tail much, has been bumping into the things in the apartment, and wasn't interested in his leash.

I've got a vet appointment for tomorrow morning. Is there anything I can do to help? Is this a common occurrence? He's my first dog and he just seems so lost

Update (copied from a comment):

His hearing has been improving tremendously. The carprofen the vet prescribed helped a lot, IMO. He's able to hear about 80% as well as he could before, though it takes him a little bit to understand. At least until he takes his medicine, then he can hear a bit better.

However, yesterday morning on his walk his front left paw started twitching and spasming uncontrollably. Poor guy was hopping around, could barely stand or even sit. He didn't seem hurt and there weren't any signs of injury (bee sting, bug bite, cuts, etc.). Took him to the emergency room immediately and they prescribed him some gabapentin. Fortunately the spasms went away and he's running and jumping around again