http://revach.net/article.php?id=1369

Section: Halacha   Category: Tshuvos
Cruel and Unusual Mesiras Nefesh
If a non-Jew tells a person that if you don't let me amputate one of your limbs I will kill your fellow Jew, is the person obligated to allow the Goy to cut off his limb? The Radbaz (3:625) says that a person is not obligated to allow the Goy to do so. However the Shach (YD 152:3) agrees with the Radbaz only if the Goy will cut off the limb with a sword which is a danger to life, however if he will cut it off with a salve it is a Safek to the Shach whether he is obligated to allow the Goy to do so.