According to Hawk (Peter MacNeill), the maintenance man reading at Johnny B. Goode (Stephen King)'s desk, Johnny is out because of his teeth. He is most likely recovering from having his wisdom teeth removed in the previous episode.
The older ambulance that follows the criminal back to the hospital is from the 1960s period. It is the same one that pulls up to the Emergency Drop-Off in Episode 1.
For some reason, not a single prison security guard accompanies spree killer Rolf (Jim Shield) to the hospital - that is not standard practice.