As far as antivenins, it is my understanding that most hospitals don't keep them on hand for the most part, and instead rely on an "antivenin bank" to fly it in when needed. Interestingly, the main bank in the US is run by the Miami-Dade Fire Rescue [1]. They have a 24 hour hotline and will arrange to have antivenin immediately flown to anywhere in the world.

[1] http://www.miamidade.gov/fire/about-special-venom.asp