Anesthetics. When you have surgery, you are basically comatose. The
drugs used to put people out for surgery (I didn't say asleep because
people who are under the knife are not asleep) can also be used to keep
people in coma for prolonged periods of time, like after the young man
who was unfortunately enough to be in a Dodge truck when the steam pipe
blew last week in NYC (he is being kept in a coma so that he can't feel
the pain of his repeated surgeries and wound cleanings with 80% burns).
Same thing for the governor of NJ after he had his SUV crash.

You can stay in a come for the rest of your life.

Jeff