Postoperative early enteral nutrition or early oral ingestion is recommended in surgical patients. In this situation, this study examined the role of parenteral nutrition in the postoperative period in patients undergoing elective surgery. The nutritional status should be assessed before surgery and in the case of malnutrition, nutritional support should be provided before surgery to obtain good results. More than 2 weeks of insufficient nutritional support after surgery may worsen the patient’s progress. Therefore, it is recommended to start nutritional care if the oral intake is not appropriate until 7 days or 5 to 7 days after surgery. Enteral nutrition is related to the quick restoration of the bowel function and reduction of infection-related complications. Therefore, enteral nutrition has priority. On the other hand, depending on the patient’s condition, it may not be possible to perform enteral nutrition, and the uniform implementation of the early enteral nutrition may be a burden to the patient. Parenteral nutrition has the advantage that it can supply nutrition without being affected by the intestinal condition, and it can be calculated to supply as much energy as required. The situation, where parenteral nutrition is required after elective surgery, could be summarized as 1) the patients who underwent nutritional therapy before surgery and could not tolerate oral intake or enteral nutrition after surgery. or 2) in the case where enteral nutrition did not satisfy 50% of the demand at 7 days after surgery, and it is judged that this situation should continue for 7 days.

Glutamine is a conditionally essential amino acid in the body because it falls into a shortage of supply during the catabolic state. Glutamine plays a key role in the gut function, immune system, and other essential processes in the body. A number of small randomized controlled trials have demonstrated positive clinical outcomes of a glutamine treatment, such as the ICU length of stay, and hospital mortality with glutamine supplementation. On the other hand, recent reports of large scale randomized controlled trials assessing the efficacy of glutamine supplementation demonstrated some negative effects and the main conclusions were a trend toward an increased 28-day mortality and significantly increased hospital stay and 6-month mortality in those who received glutamine. With such results, many academic societies have recommended that IV and enteral glutamine should not be used in a critical care setting based on the moderate quality of evidence available. The indiscriminate use of glutamine supplementation in critically ill patients with any type of organ failure can have deleterious effects. Nevertheless, more sophisticated and well-controlled larger studies will be needed to confirm how these moderate quality results are corrected and suggest the optimal usage of glutamine. More recent clinical trials have focused on specific populations and demonstrated benefits in burn and elective surgery patients with glutamine supplementation. The poor correlation between the plasma glutamine concentration and tissue concentration evoke scattered knowledge about glutamine treatments. A better understanding of the glutamine metabolism and proper guidelines for supplementation are expected.