Why does it take so long for Sepsis to clear up?

My cousin is spending his 24th night in ICU tonight. He was admitted on 11/19 with Septic shock, and has had Multiple organ failure. He was take off of the vent last week and is on the Trache. The NG tube is showing still to this day very dark green stuff coming out. On 11/29 He underwent an emergency surgery and had a 3ft section of his intestine, and lower colon removed. They tried to start him on a feeding tube yesterday, however they said his body is rejecting the tube. I asked the nurse why his body would reject it, and she told me that his intestines are still not working. His liver numbers are still "out of order". On Friday he received 2 units of blood, yesterday he got a unit, and today he got another unit. They said that his colostamy bag has blood in it, and that it may be an ulcer, or abcess. Can you lose that much blood from an ulcer?? Since the surgery, he has made eye contact however, a physicial therapist came to look at him and said that all of his movements are involuntary...