This is separate from palliative care, and the problems of hospice. For the purpose of this question, we are talking about sedating someone to the point of unconsciousness for the duration of their lives, because of great pain. Death is still weeks away, but doctors are not able to alleviate suffering without inducing unconsciousness.
On the one hand, one is fulfilling the mandate of relieving a person's pain; for more on that mandate, see Rabbi J. David Bleich's 2002 Tradition article, Palliation of Pain.
On the other hand, the idea of putting someone into a permanent unconscious state seems a lot like killing them.
I haven't been able to find much in halachic literature, but I did find an interesting response from Rabbi Dr. Mordechai Halperin, one of the leading authorities in Medical Halachah in Israel. The original Hebrew is here; my translation is below:
I wish to receive counsel and guidance regarding my 91-year old mother, who has fractures all along her spine due to osteoporosis. Recently she fell and was bounced around, and since then she has experienced great pains.
The advice of the doctors is to sedate her, to prevent pain. According to the doctors she will not return to walking, or to moving her lower body. She can move her arms lightly. However, she is still lucid.
The question: May one go along with the doctor's advice and introduce her into sedation to prevent pain? I understand that this sedation would become a permanent state for the rest of her life.
I would appreciate it if you could respond by telephone. Thank you in advance.
The discussion is of a lucid woman. Therefore, this depends exclusively upon her desire, and one should ask her directly.
What do you think? And can you provide supporting sources?