What Are The Alternates After The Foot Has Been Crushed?

my dad has been an accident where his foot was crushed. when he went to surgery to check the veins of his leg, the muscle had begun to liquify, which we were told this was causing his potassium level to be very high and because my dad has had a triple by-pass in past years, in order to save his life the foot would need to amputated. this has been done and now we are being told that he has a deep laceration in the back of his knee and there is loose skin that doesn t look like it will survive. it will be checked on friday and if it has died my dad will have to have an above knee amputation. are there any alternatives? my dad is 75, has 1 kidney and is diabetic. thank you