http://revach.net/article.php?id=4257

Section: Halacha   Category: Health
Rav Shlomo Zalman Auerbach: When A Patient Would Rather Die
If a Choleh is told that he needs a limb amputated or else he will die, may he refuse to go through with the amputation?  Rav Shlomo Zalman Auerbach (Shulchan Shlomo: Erkei Refuah - Operations) was asked this question and although he did not want to pasken he said that it seemed to him that the person is entitled to refuse the amputation.

He says that anytime a person's life can be extended through medical intervention, but it will leave him to suffer for the rest of his life, he may choose to passively forgo the procedure.  He says that in certain circumstances a person is allowed to daven for Hashem to take his life.  There are times according to the Ran in Nedarim (40a) that you may even daven that terminally ill person should die.

Amputating a leg, says Rav Shlomo Zalman can turn a respectable person in a total Nebach from the emotional scars.  Although a person is not the boss over his own life and death nevertheless this case may be different since he is not doing anything actively to end his life and it is Shev V'Al Taaseh.  Again Rav Shlomo Zalman reiterates that he is only speculating and not paskening.

Important Note: We bring this tshuvah as a starting point for discussion and not to relay any halacha.  We try to convey the Tshuva to the best of our ability. We admit that our understanding may not be accurate. One should learn the tshuva to verify the accuracy of our interpretation.  Please understand that this Tshuva may not be the final word on this topic. One should consult a Rav before drawing any conclusions.