I am a nurse and most hospitals in my area have policies that 'mandate' a nurse stay and cover the next shift if there is a shortage. Not staying to cover a shift if it is your turn is grounds for dismissal. (Not infrequently someone wants the overtime and asks to cover the shift)

As unpleasant as it sounds for the employees, you cannot leave very sick patients (and all of them are very sick these days if they meet admission criteria) without adequate nursing coverage. When I worked in a hospital, I could not do 3rd shift on a regular basis and stay healthy and sane. However, I could do it on occasion and do OK.

I wonder if you could find out roughly how often you might be needed to cover 3rd shift before you make any moves? If it is rarely, you might be able to squeak by.

Fresia - it does not sound like you are being unreasonable. Instead, it sounds like you are being thoughtful about this - both for yourself and for your employer.