Spetic in blood (CRITICAL) At this age?

My grandfather is admitted in a hospital, in ICU. He had an injury and it grew into a septic. Doctors are saying that they would have to perform an operation. He is also having low functioning liver (due to excessive medicine use, as the doctors say), hernia. He isn't diabetic, he never smoked, he age is above 82. He vomited blood a fews days back before admitting into the hospital. Doctors say that his body is not in a condition to digest any food. Perhaps they are gonna perform the operation tomorrow to remove the septic. But they are not stating the problems clearly. Just left the decision to us, whether or not to perform the operation. Please suggest something. Or atleast make the condition of septic clear, or what exactly happens due to septic and how such an operation is performed. And is it dangerous to perform the operation at this age? Thank you.