It should be avoided at all costs,
patients in hospitals arent dieing horses in the battlefield,
most of the times there is still a fragment of hope even in the worst cases scenario,
i m not speaking about miracles here, but new tehniques/treatment should be tried out first,
even a desperate surgical operation attempt is better than that
and the patient doesnt have to suffer or even feel anything,
modern medicine is beyond that, i can hardly think of any chance a conscious patient would be presented to such a situation and willingly take that...decision...
doctors wont allow a patient to sucide, even if he wises to
and a doctor should not be obligated by law to take a life at almost any circumstances...esp when the patient dissagrees to follow a treatment because of his religius/spiritual/social believes.
BUT unfortunately there are some very very rare cases, when, honestly there is no other way...