The patient’s nutritional requirements are increased by surgery for several reasons. First, there is a period following surgery during which oral intake is not allowed or is very limited. In addition, the operation itself causes increased protein catabolism, increased energy requirements, and a negative nitrogen balance. If the surgery is uncomplicated and the patient is without food for less than 7 days, this response is limited and patients usually recover without the need for nutritional support. An adequate diet is defined as providing 75% of estimated caloric and protein needs. Therefore, if an adequate oral diet is not expected for 7 to 10 days, perioperative nutritional support may be required to avoid progressive malnutrition and associated complications (14). Perioperative nutritional support reduces operative morbidity and decreases the length of hospitalization when commenced early in the postoperative course. Patients with either normal nutritional indices or mild or moderate malnutrition, who will be undergoing surgical procedures likely to require a prolonged catabolic period of more than 7 to 10 days, should have enteral or parenteral nutrition instituted in the early postoperative period as soon as the patient is hemodynamically stable. This type of management should be strongly considered in patients undergoing pelvic exenterations, urinary diversions, or multiple enterectomies (16). Preoperative nutritional support is indicated for patients who have significant preexisting malnutrition or require major elective surgery. According to the American Society for Parenteral and Enteral Nutrition (ASPEN) guidelines, evidence-based medicine supports the use of preoperative nutritional support for 7 to 14 days in moderately to severely malnourished patients undergoing major nonemergent gastrointestinal surgery (12). A Veterans Affairs Total Parenteral Nutrition Cooperative Study found that severely malnourished patients preconditioned with total parenteral nutrition (TPN) had fewer complications than did control patients, excluding infectious complications (17). In a meta-analysis review of 22 studies of preoperative TPN use, a 10% decrease in postoperative complications occurred in TPN-supported patients (18). In a prospective trial including 108 women with ovarian cancer who underwent surgical cytoreduction, 88 patients had prealbumin levels less than 18 mg/dL and 24 had prealbumin levels less than 10 mg/dL (19). All postoperative mortality (23%) and 61.5% of all complications occurred in women with prealbumin less than 10 mg/dL. Women who received preoperative TPN and had prealbumin levels that increased to greater than 10 mg/dL did not have significantly increased complications. These findings lend support to consideration of preoperative TPN or neoadjuvant chemotherapy with interval cytoreduction when the nutritional status improves. These findings are encouraging but not supported by all studies or meta-analyses (20). If preoperative TPN is prescribed, it should be tapered and stopped at midnight before surgery, restarted 24 to 72 hours after the procedure, and continued until the patient is able to meet nutritional requirements.
ASPEN guidelines do not support the routine use of nutritional support in the immediate postoperative period for patients undergoing major gastrointestinal surgery; however, the guidelines do indicate a role for nutritional support postoperatively in patients in whom oral intake will be inadequate for 7 to 10 days (12). Clinical trials demonstrate that TPN can improve nutritional status as measured by biochemical assays, immune function, and nitrogen balance. The effect of TPN on clinical outcome is less well established. Despite what seems reasonable, based on common sense and preoperative nutritional parameters, the data do not support TPN for mild to moderately malnourished patients. With severe malnutrition, preoperative TPN seems to be beneficial and should be instituted.