The goal of this clinical trial is to compare the clinical effects of using Ringer's Lactate and Sterofundin/ Plasmalyte as maintenance fluids in adult patients who have undergone abdominal surgery and are septic. The primary outcome will be the change in serum lactate levels. Secondary outcomes will include renal function parameters, qSOFA scores, and the incidence of postoperative complications within the first 72 hours following surgery.