In America, parenteral nutrition is ordinary care. If it is withdrawn, the patient does not die from their disease process, they die from dehydration.
The proximate cause of death, to use traditional medical ethics terminology, is dehydration, not the disease process that caused the inability to swallow.
Unless the patient cannot assimilate the fluids and food, even if by tube, it is ordinary care in Christian teaching, not extraordinary.
That may not be the case in certain Third World nations, where parenteral nutrition would be so expensive as to relegate it to extraordinary care due to the burden on the family and/or society.
But in America, today, it is ordinary care according to any orthodox understanding of medical ethics.
That could change in the future, given circumstances that are not unlikely, but at present, there is simply no excuse not to give people food and water, even if "artificially" delivered. A drink of water is a drink of water, food is food, both are basic human rights, regardless of how they are delivered. At least according to orthodox Christian medical ethics.