The patients staying in ICU for more than 24 hours were enrolled in the study. Patients received anti-inflammatory drugs or corticosteroids before admission, patients had immunosuppressive illness, patients had chronic organ failure; patients received massive blood transfusion; patients with radiation therapy and patients with previous organ transplantation were excluded from the study. At admission, patient's age, sex, weight and height were recorded. Patients data that include the clinical status; sequential organ failure assessment (SOFA) score; temperature; heart rate; respiratory rate; blood pressure; central venous pressure; laboratory analysis (complete blood count, blood urea nitrogen, blood sugar, serum sodium, potassium, calcium, aspartate aminotransferase, alanine aminotransferase, prothrombin time, albumin and CRP) and arterial blood gas analysis were measured. Routine cultures of suspected sites, blood and urine were obtained to determine the presence of infection. We attempted to maintain the patient hemoglobin level at 10-12g/dl and central venous pressure at 8-12 cmH2o. When needed, intravascular fluid replacement, blood products and inotropic or vasopressor agents were administered. Each day the attending physician evaluated all the study patients for sepsis, severe sepsis, or septic shock as long as their stay in ICU.