The next time you're talking privately to one of your employees, find a way to work this question into the conversation: "what can I do to make this a better workplace?"
So that he/she doesn't feel blind-sided or become suspicious, frame it in such a way that you're concerned about every employee's satisfaction with their job as a means to reduce turnover. As an empowered healthcare manager, you are perpetually concerned about this, which makes your framing absolutely true. High turnover rates caused by employee dissatisfaction hemorrhage resources like nothing else.
This question is powerful for two reasons. 1) the answers you get will be incredibly revealing about each employee you ask; 2) merely asking the question is incredibly revealing about you.
It tells everyone you ask that their supervisor wants them to be long-term team members. That will blow some of them away. For many members of your team, no employer has ever asked them that question, which is by itself sad. It's also likely no one in their circle of friends has ever been asked that question by their supervisors, either. At the end of the day, when they share what you asked them with their family and friends---and they will---it will become obvious they have an exceptional supervisor. Don't underestimate the power of that revelation.
It will have the greatest impact on those employees who are marginal keepers, not your top-performers. Top-performers already are with you for the long haul. (They should be asked the question regardless; it will further reinforce their longevity with you.) But those who might not be fully engaged will be the greatest benefactors of your question. Perhaps the only thing that's keeping them from fully embracing their place on your team is not knowing you are interested in keeping them long-term. It may be all they need to step up.
But do not ask this question of someone you don't want to keep. It creates a false impression, and will confuse the rest of the staff when they find out.
Make no mistake; the question is a double-edged sword. The answer(s) you get have to be acted upon. Not necessarily granted, but acted upon. If they're ignored, you will be seen as insincere and your potential top-performer becomes a potential past-employee.
If "more money" is the response, and you know that's not possible, acting on it means explaining to the employee why it isn't possible, and bringing it to the attention of your superiors anyway. The "more money" crowd will never be satisfied, but you have to follow through. If the response is "do something about [adversarial coworker]," you had better take steps, lest you be seen as part of the problem.
This revealing question will empower you and those to whom it is posed. Few questions have that kind of impact.