As for the other complications about real names, etc, They would all come secondary to the well being of the lady to me.

If it turns out she is dead, then she would be beyond caring about what she was doing and if she was just seriously ill then the most important thing would be getting her help, any questions can be handled later. I doubt the medical team or even police if they were called are going to really care that much about her being a hooker or me being a john, but even if they were, that's a risk I would be willing to take. I can't see how NOT calling for help would even be an option that I would consider.

Gets very sick (unconscious)... or drops dead right in front of you?   Lets assume that it's NO fault of your own. You are innocent but the situation just escalated to be 'pretty damn serious'.  

Anything else.   Call 911 in either situation.  Besides, it's the right thing to do.

A hobbyist died on a provider a few weeks ago.  Cardiac arrest. She did the right thing. She called 911, and stayed to answer questions to the paramedics and police. She was not charged with anything. But she was very shook up. She is taking a break from providing.  

is helping another human being.

Because it gave us all time to reflect.  
I would call 911 & hotel desk, unlock door.  Render first aid to the best of my ability until first responder arrived.  If I/she was undressed, I'd grab clothes & lock myself in bathroom.  

You have a duty as a human being to render aid in an emergency. This goes double if you know them. You do the right thing and figure the rest as it comes. I doubt the cops would even care in that situation. They might care though if you just left.

My track record in upsetting situations isn't very good....

This has gone around a few times, but it can't hurt to repeat it  

Shit happens and anybody in their right mind would want to do the right thing.  it's good to have a plan though.

The provider calls 911 but the client dies before they arrive, autopsy shows he was poisoned. What do you think?

"escort found dead by some drunk John.  Experts claim something was wrong with her health"    

Her client had a seizure during a session, so she dialed 911 and stayed with him until the ambulance arrived.  Now she introduces him at parties as "Stroke Guy."

Even the simplest neutral words such as 'stroke' seems to bring up in my mind images of giving strokes of hand jobs.  

And I believe the lady in question was stroking him at the time.

probably the most famous case ever about this, http://www.reformation.org/megan-marshak.html
She went on to work as a writer in NYC media and was known as "Killer Pussy"

Dood, I've gotta stop opening your posts mid sip. Coconut water all over my mac.
He be stroken'!!! Stroken to the left, stroken to the right…  

Cuming and going at the same time, perfect.

It's good to know that the majority of posters would call 911 and deal with the situation in a mature way. They'd do the right thing. At least in my book.

Life is too important to play around.  If for some reason the person stopped breathing, God forbid, I'd try CPR (I am certified) if warranted and definitely stay and cooperate with authorities because, I know that I didn't do anything to cause it, and as was said earlier in this thread, the cover up makes you look like a suspect.  Providers are people too and deserve basic humanity when they fall ill.  Anyone who would disagree with this is simply inhuman and a psychopath whom you should stay away from.