Current concepts on preoperative nutritional support: How, when and why?

Malnutrition is associated with several complications during hospital stay, including patients who will undergo major surgery. Therefore, it is important to optimize nutritional status in the preoperative period being the main objective restoring metabolic and immunological abnormalities. Preoperative fasting is a common practice in clinical settings, although it has been shown to induce insulin resistance. One intervention to avoid this practice is the implementation of the ERAS (Enhanced Recovery After Surgery) protocol. Proper nutritional assessment in hospitalized patients is the cornerstone to identify patients at nutritional risk, or those in malnutrition who may benefit from early nutritional interventions. The feeding route should be chosen according to the patient's condition, either orally with the use of nutritional supplements and in those where calorie requirements cannot be achieved by oral, enteral nutrition is the next logical step, reserving parenteral nutritional support in patients with non-functional gastrointestinal tracts in order to improve postoperative morbidity and mortality.