**3.8 Parenteral nutrition**

EN is the first way of nutrition, however, if it is not possible to use it or there is intolerance to it, parental nutrition (PN) can be used, which is used after the fifth or seventh day of admission to increasing, in this way, the correct clinical development of the patient and decrease the hospitalization days [40, 59, 89, 92, 93] EN intolerance is generally accompanied by diarrhea and in such cases, PN nutrition is considered. It is recommended that PN must have a gradual increment starting from day one up to

day three in the following way 50%, 75%, and 100%, and must include carbohydrates, proteins, and lipids. The control of the hemodynamic status of the patients has to be overseen even before starting the nutrition in order to avoid the re-feeding syndrome in such a way that the formula can be readapted if required [1].

An important consideration is that glucose should not be more than the maximal level of glucose oxidation (4–7 mg/kg/min or 5–6 g/kg/d), and a target blood glucose range of 7.7–10 mmol/L is recommended [94, 95]. Intravenous lipid emulsions can be safely started, and the recommended dose is 0.8–1.5 g/kg/d [40, 41]. Intravenous lipid emulsions dose may need to be reduced or discontinued if serum triglyceride consent iterations are greater than 4.5 mmol/L [96, 97]. In PN-exclusive nutrition, a daily dose of multivitamins and trace elements should be administered. Micronutrients should be supplemented in patients with confirmed or suspected deficiencies of estimated nutritional requirements gradually from day 1 to day 3. The hemodynamic status must be watched to avoid water/electrolyte and acid-base imbalances [1, 41].
