this an example why GAs are not always needed in dentals, if a dental pig most of the time always a dental pig and they need dentals every 2 weeks for a while before they can go longer between.
the thing you need to do is keep him warm as he is likely to have dropped his temp, ie use a wrapped water bottle or a snuggle pad if you have one.
i would be careful trying to syringe feed water due to the fact he still has GA in his system the water could go into his lungs.
he really does need to see a emergency vet asap meaning now!
he will need iv fluids, Metoclopramide given via injection and then given oral from 2moz 3 times a day until he is eating and his poops are normal, this is a gut stimulant= his gut will be slowing down now due to him not eating.
how much Metacam has he had?
do you have any pellets in?
if so put some into a cup/bowel and pour boiling water on them to cover them, wait 15mins then add more water, wait another 15 mins then stir with a fork until a smooth paste, wait for the pellets to go warm to cold and use a 1ml syringe, when putting the syringe into the mouth you need to go behind the front teeth aiming to where the back teeth are, aim for 30-40ml per sitting which should take around 20mins to do BUT with him still having GA in him i would aim for this over a longer time 40 mins dont shoot the syringe contents into the mouth fast because with him still having GA in his system his swallowing reflex will not be the same and it could go into his lungs.
but its important he has iv fluids now to hydrate him and give him a better chance of getting the GA out of his system, if you wait there is a chance he will die, its that serious.
ring Cambridge Cavy Trust and ask Vedra for you nearest Rodentologist who normally do dentals free and with out GA.
did they find any teeth problems?