You don't need to give an explanation.. They are in your hospital room without being invited. If you feel up to explanation going ahead but you can simply ask them to leave.

"Coincidental" to another thread on this fine priest, the preface or first chapter (I forget) of Our Saviour and His Love for Us / Fr. Reginald Garrigou-Lagrange, discusses the fact that there are no coincidences.  Every single solitary person who comes into our sphere each day is purposefully willed by God, and it is our duty to convert them, most likely by our demeanor: "Preach the Gospel at all times; when necessary, use words."

Reading that book completely changed my perspective on so called chance encounters, or even something as commonplace as sharing a subway or bus or sidewalk with strangers.  The Holy Ghost will use His humble servants to plant seeds.  An EM visit is a great opportunity!
My approach is to hand them a docuмent with some info and references, smile and ask them to pray for me, as I will for them.  I've been doing the same for all Jehovah's Witnesses/7th Day Adventists (handing them pre-printed info of their teachings vs Catholic) when they come to my door, so why not a baptized Catholic?  
Perhaps because I was one of them thar EM's not so long ago I go to too much effort?   This is where a dunce cap smiley would work well....

Kill them with kindness, it will drive them crazy!   a dancing banana backatcha Pete   :dancing-banana: