Everyone asking what positions were affected, as if they can do anything about it with such late notice. If you're finding out people in your position are being impacted now, it's far too late to do anything.
All you're accomplishing is getting a few hours or at best a day advance notice.
If you want to be pro-active, get ahead of the curve and read the writing on the wall. There's a REASON this merger is happening, and the execs are doing this, and it's not because things are so rosy, although I'm sure management would happily fill your ears with that corporate BS.
And the reason is the entire healthcare industry is in crisis mode. Hospitals declaring bankruptcy and closing, massive layoffs everywhere from Pfizer to Merck and everything in between. Knowing this will allow you to see the big picture and make a better decision, although of course those who can't handle change will call it fearmongering, because they fear.
No, this is called information, and I'm sorry, it's not always good news. Welcome to the real world cupcakes. Now, get proactive, find out what's really going on and act like an adult.