Parenteral Nutrition (PN) is prescribed to children with a non functioning gut. Timing of initiation of PN for critically ill children is a hotly issue. Therefore investigators aim to determine the optimal timing of initiation of PN among these children.This is a randomized clinical trial will be conducted at a Pediatric Intensive Care Unit(PICU) in tertiary care hospital. 140 participants will be randomized to receive either early or late PN. The 1st group gives PN on the 1st day of PICU admissions while the 2nd group gives late PN on the 7th day. Under-nutrition children, early PN will start on the 1st day while late PN begins on 4th day of admission. The outcomes are assessment of mechanical ventilation duration, PICU length stay, and mortality.

Participants and Methods:

This is a single-center; open-label randomized controlled trial will be performed at a Pediatric Intensive Care Unit (PICU) in tertiary care hospital . On admission, patients will be evaluated through history, clinical examination, and investigation.Basic investigations will include complete blood count, serum electrolytes, blood gas analysis, serum creatinine and liver function tests. The severity of the clinical condition upon admission will be determined by calculation of pediatric Sequential Organ Failure Assessment (pSOFA) score and Pediatric Risk of Mortality (PRISM) at the end of the first 24 hours. Patients will be randomized to receive either early or late parenteral nutrition. Early parenteral nutrition will be given in the 1st 24 hours of admission while late parenteral nutrition will be initiated on 7th day of admission. Randomization will be performed by using computer generated random numbers.The patients and the treating physicians will be not blinded to the type of parenteral fluids given. For children with moderate/severe under-nutrition, early parenteral nutrition will start on the 1st day while late parenteral nutrition will on 4th day of admission. This difference in timing of feeding is based on the fact that malnourished children have limited energy reserves and insufficient nutrition for 6 days might be too long a period compared with the case of well-nourished children. Parenteral nutrition consists of glucose, protein, electrolytes (sodium, potassium, calcium, magnesium, and phosphorus), trace elements, water soluble vitamins, and amino acid solutions.Lipid emulsions will be given . The nutritional status of patients will be carefully assessed. The admission weight and length/height will be recorded and a patient will be deemed to have under-nutrition if weight for length z-score is ≤ -2 SD. For children > 36 months, weight/age z-score ≤ -2 SD is used , instead, to define under-nutrition because measuring the height is difficult for critically ill children.

Patients' eligibility inclusion criteria:

• Critically ill children admitted to PICU for various reasons and unable to receive their full caloric requirements through the enteral route will be eligible for this study.

Exclusion criteria:

• Included expected short PICU stay < 3 days e.g. Diabetic ketoacidosis;
• Age under 1 month or over 16 years.

open-label randomized controlled trial performed at a Pediatric Intensive Care Unit (PICU) in tertiary care hospital

A). Primary outcome for assessment of participants who need mechanical ventilation(MV) and MV duration.

B). Secondary outcomes will include assessment of participants accordingly, Pediatric Intensive Care Unit (PICU) stay , days of need for vasoacitive drugs infusion , incidence of new infections ,and PICU mortality.