Malnutrition is associated with negative impact on morbidity and mortality of critically ill patients. Therefore, in patients unable of peroral intake, the nutritional support is indicated. The preferred form of nutritional support is enteral, the more natural form, compared to parenteral. The enteral nutrition is cheaper and is associated with better outcomes and lower incidence of associated complications. The intolerance of enteral feeding is common in critically ill patients, and is associated with insufficient energy and protein intake, that could be linked with the complications such aspiration pneumonia. The optimization of enteral feeding tolerance is therefore one of the research priorities. Implementation of feeding protocols is associated with better tolerance. The enteral feeding could be administered as a oligomeric or polymeric formula. The are preliminary data from adult population pointing at better tolerance of oligomeric feeding formula.

After Ethics Committee approval, all paediatric patients admitted to the paediatric intensive care unit (PICU) will underwent PICU screening. In case of eligible for inclusion in to the study, the baseline parameters a demographics will be evaluated together with the initial laboratory sampling after approval and singed the informed consent by the legal guardian of the patient. Patients will be randomized by the online randomizer to the oligomeric and polymeric enteral nutrition group.

Polymeric (control group): Patients indicated for at least 2 days of enteral nutrition by the gastric tube. The nutritional support will be initiated after initial haemodynamic stabilization (blood levels of lactate normalization, norepinephrine infusion <0,1 ug/kg/min) in the 48-hours interval from admission in form of bolus administration of polymeric formula 1ml/kg/dose. The gastric residual volume will be evaluated after 4 hours from bolus dose. In case of gastric residual volume lower than half of previously administered dose, the next dose will be doubled. In case of higher residual volume, the same amount will be administered with the metoclopramid (3 times per day). In case of persistent residual volume higher than half of initial dose in 12 hours, the erythromycin will be initiated for 3 days. The bolus enteral feeding will be administered at the predefined time 5/day (6:00, 10:00, 14:00, 18:00, 22:00). The las gastric decompression is planned ad 24:00. The aim is to reach energetic goal defined by Schofield equation.

Interventional (oligomeric group): Patients indicated for at least 2 days of enteral nutrition by the gastric tube. The nutritional support will be initiated after initial haemodynamic stabilization (blood levels of lactate normalization, norepinephrine infusion <0,1 ug/kg/min) in the 48-hours interval from admission in form of bolus administration of oligomeric formula 1ml/kg/dose. The gastric residual volume will be evaluated after 4 hours from bolus dose. In case of gastric residual volume lower than half of previously administered dose, the next dose will be doubled. In case of higher residual volume, the same amount will be administered with the metoclopramid (3 times per day). In case of persistent residual volume higher than half of initial dose in 12 hours, the erythromycin will be initiated for 3 days. The bolus enteral feeding will be administered at the predefined time 5/day (6:00, 10:00, 14:00, 18:00, 22:00). The las gastric decompression is planned ad 24:00. The aim is to reach energetic goal defined by Schofield equation.

Inclusion Criteria:

• PICU patients indicated for nutritional support by enteral feeding (gastric or jejunal)

Exclusion Criteria:

• Enteral feeding contraindicated
• Persistent haemodynamic instability
• Informed consent not signed
• Acute pancreatitis
• Recent upper gastrointestinal surgery
• Gut perforation
• Ileus

The patients and the legal guardians will be blinded