• Length of stay in ICU and the hospital [ Time Frame: 2 years ] [ Designated as safety issue: No ]
  

• Death (hospital and ICU mortality) [ Time Frame: 2 years ] [ Designated as safety issue: Yes ]
  
• Days to weaning from mechanical ventilation [ Time Frame: 2 years ] [ Designated as safety issue: No ]
  
• The need for renal replacement therapies [ Time Frame: 2 years ] [ Designated as safety issue: No ]
  
• The presence or absence of new kidney injury during intensive care [ Time Frame: 2 years ] [ Designated as safety issue: No ]
  
• Days of vasopressor or inotropic support [ Time Frame: 2 years ] [ Designated as safety issue: No ]
  
• The presence or absence of hyperbilirubinemia and liver steatosis [ Time Frame: 2 years ] [ Designated as safety issue: No ]
  
• The need for tracheotomy [ Time Frame: 2 years ] [ Designated as safety issue: No ]
  
• The presence or absence of hyper-inflammation within five days after ICU admission [ Time Frame: 2 years ] [ Designated as safety issue: No ]
  
• Blood lipid profiles and albumin on days one, five, ten, and fifteen after admission [ Time Frame: 2 years ] [ Designated as safety issue: No ]
  
• The presence or absence of bacteraemia, ventilator-associated pneumonia and of wound infections [ Time Frame: 2 years ] [ Designated as safety issue: No ]
  
• Episodes of hypoglycaemic events (defined as glycemia less than 40 mg/dl) [ Time Frame: 2 years ] [ Designated as safety issue: No ]
  
• Amount and type of calories delivered [ Time Frame: 2 years ] [ Designated as safety issue: No ]
  
• Muscle strength and rehabilitation [ Time Frame: 3 years ] [ Designated as safety issue: No ]
  

Written informed consent will be obtained from the patient or the closest family member or legal guardian. The family member or the patient can withdraw from the trial, at any time, without impact on his treatment or penalty. The investigators confirm that this study concerns a condition that directly threatens patient health and that the adult patient not able to give consent suffers from the condition. The experiment is essential to confirm the results from earlier research in patients who could consent or from other research methods.

On admission patients will be randomly assigned to receive EN combined with early PN or only EN. At ICU admission, consecutive patients will be randomly assigned to one of these two treatment groups using blinded envelopes, stratified according to primary diagnostic category on admission.

As initial nutritional support, patients randomised to the 'EN combined with early PN' group will receive glucose 20% at 40 ml/hr. EN will be initiated in the evening of the second ICU hospitalisation day, PN will be started the morning of the third ICU hospitalisation day. The amount of PN to be given on any particular day will be the difference between calculated caloric needs and the calories delivered by EN the previous 24 hours. When EN covers 80% of calculated caloric needs PN will be stopped. When the patient is able to eat, the parenteral regimen will be reduced and eventually stopped. Whenever oral (+ enteral) intake is below 50% of calculated caloric needs, the PN will be (re)-started.

As initial nutritional support, patients randomised to the 'EN only' group will receive glucose 5% at 40 ml/hr. EN will be initiated on the evening of the second ICU day. From the morning of the third ICU hospitalisation day on, the amount of glucose 5% to be given will be the same as the volume of PN the patient theoretically would require to receive 100% of presumed caloric needs based on the amount of EN delivered the previous 24 hours. When the patient is able to eat, the parenteral regimen (glucose 5%) will be reduced to 50% and eventually stopped. Whenever oral (+ enteral) intake is below 50% of calculated caloric needs, the PN (glucose 5%) will be (re)-started. If these patients would need to stay for more than seven days on the ICU and enteral feeding of at least 80% of the calculated calories is not possible, they will be switched to EN and PN on day eight.

Common strategy for attempting early enteral nutrition in both study arms:

EN will be initiated on the evening of the second ICU day, unless patients are able to eat. The increase of enteral feeding volume and the adaptation of the regimen to pathological conditions will be according to protocol. Trace elements, minerals and vitamins will be administered daily intravenously (IV) to all patients from the day of admission onwards. IV substitution will be stopped in patients receiving at least 1500 ml of EN. All patients will be treated following the intensive insulin therapy schedule - targeting a blood glucose level of 80 - 110 mg/dl - from admission until discharge or oral feeding.

Patients will be weaned from the ventilator according to a standard protocol. End-of-care decisions in patients for whom further intensive care is considered to be futile will be taken in consensus by a group of two senior ICU physicians and the referring specialist, all blinded to study treatment allocation.