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.