What is an impaired nurse? What would you do if you encounter an impaired nurse while on-duty?

What is an impaired nurse? What would you do if you encounter an impaired nurse while on-duty?

I need at least 2 references including

-Westrick, S. J., &Dempski, K. (2008). Essentials of nursing law and ethics. Sudbury, MA: Jones and Bartlett Learning