Replacing Protein Via Enteral Nutrition in a Stepwise Approach in Critically Ill Patients

Inclusion criteria 1. Age ≥ 18 years 2. Mechanically ventilated 3. Receiving enteral feeding via nasogastric/orogastric or duodenal or PEG or jejunostomy tubes and 4. Expected to stay ≥ 1 week in the ICU Exclusion criteria 1. Lack of commitment to ongoing life support, which includes; * Terminal Illness (Malignancy or irreversible condition with 6 month mortality \> 50%) * DNR order in the first 48 hours and brain death within 48 hours of admission) (Don't include the presence of a "Do Not Resuscitate" order alone, if there is a commitment to ongoing life support). 2. Patients not fed within 48 hours of admission 3. Patients on total parenteral nutrition (TPN) 4. Patients being fed orally 5. Chronic renal failure 6. Chronic liver disease 7. Renal replacement therapy 8. Pregnancy. 9. Kidney transplant 10. Post-liver transplant. 11. Post cardiac arrest. 12. Burn patients. 13. Prisoners Screened patients will be screened again for eligibility at day 5, should be mechanically ventilated and expected to stay ≥ 3 days in the ICU. At this point, patients will be excluded if they meet the following; 1. New onset renal replacement therapy. 2. Acute Kidney Injury (serum creatinine \> 3 times the preacute level or serum creatinine \>350mmol/L with a recent increase of \>44 mmols/L) 3. Significant liver impairment