I tried googling an answer to your question without much luck. I believe that the hospital models are changing due to the economics involved. Back in the day, large hospitals, like Mass General had several thousands of beds but, just as airliner size is "downsizing" due to the changing economy, I think that hospital size is also changing. Interesting question. Maybe someone with hospital admin background will give a definitive answer.
When I worked in a 1200 bed county hospital, I had a per diem gig at a "small" 400 bed community hospital, this was in metro NY. I now work in northern New England at a 25 bed hospital, the closest major tertiary care center is about 400 beds and considered huge.