HI,
I ve heard that more people die from problems from anesthesia than from the surgical procedures, to put you to sleep they have to put you down to the point you need assistance to breath and are very close to the level required to stop your heart, its a delicate procedure and not everyone repsonds the same way, sometime people have blood clots from laying still so long and a slow pulse and that can cause a stroke or a lung emoblism that can be fatal. and there's always a risk of contracting an infection.
I had a 6 hour procedure done once that requred considerable meds to reverse the anesthesia and finally wake up and nearly three days to clear it all and walk again. Dr said that happens sometimes..
Doug