Table 2 Inclusion and exclusion criteria - patients are included if thay meet all three criteria, and are excluded if they meet one or more of the following criteria

SAPS II ≥ 32 points

Neurosurgical patients

Estimated length of mechanical ventilation at ICU admission ≥ 3 days

CNS diseases (epilepsy, stroke, dementia, post-anoxic coma)

Age ≥ 18 years

Liver encephalopathy (Child-Pugh C)

Previous psychiatric or cognitive pathology

Allergy to medications used in the study

Absolute contraindications to the use of enteral route (nasogastric tube, nasojejunal tube, jejunostomy, ileostomy are all considered acceptable)

Pregnant or breast-feeding patients

Death is deemed imminent and inevitable or the patient has an underlying disease process with a life expectancy of < 90 days