Regarding whether using anesthetics for a long time is dangerous, of course it is. Using anesthetics at all is dangerous. Unconsciousness, even on the order of minutes is possibly (and even likely) lethal. Mortality due to anesthesia in surgical procedures is presently at 0.4/100,000 in Europe (used to be 8/1,000 in the 1960s). So, yes, you can die just like this, even with a dedicated person watching your body in super-paranoia mode, only because of anesthetics.
Note that when I say "super paranoia mode" this means that persons under anesthesia normally have much better vital parameters than you do in normal life, the anesthesist makes sure of that.
Is it possible to hold a person unconscious for a year without serious defects? In principle.... sure.
You will need either a PEG tube or intravenous feeding, which works reasonably well nowadays, monitoring, and you will need a clinitron bed and a dedicated nurse at the very least. Also, you will need a physiotherapist visiting daily, and you will have to perform transcutaneous electrostimulation.
So... if three thousand or so dollars per day are no problem, then sure, you can do it. Not that I'd recommend it.
The solution proposed by @Will is much preferrable due to its cost effectiveness and safety. Doesn't have to be thorazine, there's a couple of drugs that will do well for the task. Dim the light a bit, cage the window, close the door, and you're good to go.