# Perioperative Nutritional Support: A Review of Current Literature
## 5 Perioperative Nutritional Support in Oncological Pathology
### Gastrointestinal Cancer
Patients with pancreatic cancer present with a high prevalence of malnutrition, measured both by weight loss and screening tools [88; 89; 90]. Surgery for this type of cancer is inherently at high risk of complications [91] and it has been classified as the surgery with the highest risk of 30-days readmission [92]. One of the most important risk factors for complications after pancreatic surgery is precisely malnutrition, which has been associated with a higher number of pancreatic fistulas [93; 90], abdominal abscesses [88], hospital readmission [94], in-hospital mortality and 90-day mortality [88]. In fact, early identification of malnutrition and its treatment during admission has shown to reduce morbidity, length of stay and costs in these patients [95; 90]. Several studies have been performed regarding perioperative nutritional support in patients undergoing pancreetoduodenectomy (PD). With respect to parenteral nutrition, the results obtained showed an increase in infectious complications, morbidity, length of stay and mortality when compared with intensive fluid therapy [96], standard enteral nutrition [97; 98], enteral nutrition with immunohistochemistry [95; 99], and oral diet [99]. On the other hand, enteral formulas with immunohistochemistry have also been compared with other enteral nutrition standard formulas, showing a decrease in postoperative infections and length of hospital stay [99; 100; 101]. In 2007, [PERSON] et al. [102] conducted a study in which postoperative complications were reduced in cancer patients undergoing PD with different degrees of malnutrition when fluid therapy was switched by parenteral nutrition, parenteral nutrition by standard enteral nutrition and the latter by enteral nutrition formulas with immunohistochemistry. Based on the results of these and other similar studies, ESPEN already in 2006 recommended the use of perioperative enteral nutrition (preferably with formulas containing immunonutrients) in patients undergoing PD (grade A) [103]. However, the ERAS guidelines for patients undergoing PD, updated in 2019 [104], recommend preoperative nutritional support in patients with severe weight loss, but do not recommend the use of immunonutrition formulas, with a high level of evidence and a strong grade of recommendation. This statement was based on the scarce data in patients undergoing PD and the heterogeneity of methodology and results in studies performed at present. In 2016, [PERSON] et al. [105] performed a meta-analysis showing a decrease in morbidity and delayed gastric emptying in patients who followed ERAS protocols after undergoing PD, although this had not been demonstrated in a 2013 meta-analysis performed by [PERSON] et al. [106]. In 2018, [PERSON] et al. [107] conducted a new meta-analysis including 20 case-control studies with a total of 3694 patients, concluding that the implementation of ERAS protocols was safe and effective and could reduce postoperative complications. However, clinical practice studies show that the protocol established by the ERAS guidelines regarding early initiation of oral diet is not frequently followed, since its initiation is usually delayed and the progression of oral tolerance is usually slow, and the caloric requirements of the patients are not reached in the first days [108]. In 2014, [PERSON] et al. [109] conducted a study in patients who underwent PD, comparing those who started liquids on 1 st post operative day (POD) and solids on 2 nd POD post-surgery vs. patients who started them on 3 rd POD and 4 th POD, respectively. The results showed that low compliance with ERAS targets was associated with a higher rate of complications and greater severity of complications. Therefore, authors such as [PERSON] [108] recommend the use of enteral nutrition by nasojejunal tube or jejunumostomy (depending on the patient's preferences) until the caloric and proteic requirements with oral diet are reached, appealing to its low risk of complications.