I. Background Excessive fluid loss is often reported in gastrointestinal surgical patients due to preoperative fasting and bowel preparations. Many factors may further exacerbate the lack of fluid volume, including intraoperative blood loss and fluid loss, anesthetic drug-induced peripheral vasodilatation, as well as systemic inflammatory response syndrome, systemic capillary leak syndrome, endothelial barrier dysfunction and transfer of intravascular fluid to the third space caused by surgical trauma.