Or try spamming the alt button. Worked for me.

I started bleeding out from a zombie attack. When the "You are unconscious" screen popped up, I figured, "Okay, I'll probably die soon"

After waiting 30 minutes, I felt it was going no where and hit "re-spawn"

Nothing happened. After five minutes a "You are dead now" screen popped up and I respawned.

Being unconscious doesn't particularly bother me, however; I don't know if another player can help you regain consciousness or not. If there were ways for other players to help wake you up, that'd be nice.

I'd prefer to not be unconscious forever. :I