2 years off the floors... need advice on restoring fading skills

I'm an occupational health nurse. I like my job, but I feel like the longer I do this sort of work, the more screwed my career is. I want to get into some acute care as a per-diem so that I can maintain my experience.

It was a bit disheartening to have a nurse staffing agency reject my application based on being out for 2 years.

Any advice? I'm already working on a RN to BSN.