Cat Not Drinking?

I've got a cat, Mufasa, who's an indoor/outdoor cat and came in around 12 hours ago with his tongue all cut up. There wasn't much blood and though it's still pussing, the possibility of infection is something I can take care of by going to the vet after work. However, he isn't drinking. I've been able to force a few mL of water down with a syringe, but I have to be at work in 4 hours for a twelve hour shift, and the major concern I have right now is dehydration. Currently I'm trying to get him to drink at least a little more. When should I start to consider it a major immediate emergency? Can a cat really go 24+ hours with little water? It seems doubtful to me but my maternal instincts might just be kicking into overdrive.

Getting him to the vet sooner rather than later is the best. Is the appointment scheduled for today? Has he been eating? Though cats don't need much water they will get dehydrated fighting off infection pretty quickly. So if he's not eating and not drinking see if you can drop off your cat to the vet before you go to work so he can be observed.