A 8 year old male child underwent laparotomy with adhesiolysis for acute suppurative appendicitis, perforated peritoneum with intestinal obstruction and adhesions in abdomen with sepsis. Patient was well after the surgery and was discharged as the vitals were stable, again after 5 days patient comes back to hospital with complaints of fever, pain in the abdomen, upon investigation low patelets count around 26,000 and CRP of 80, CT-Scan abdomen done Normal, patient is on Imipenem 0.5gm 4 times daily and fever is showing spikes, what would you suggest?