Disruption of circadian rhythms is frequently observed in patients in the intensive care unit (ICU) and is associated with worse clinical outcomes. The ICU environment presents weak and conflicting timing cues to the circadian clock, including continuous enteral nutrition. The goal of this clinical trial is to evaluate the effect of timing of enteral nutrition on the circadian rhythm in critically ill patients. Patients admitted to the intensive care unit will be allocated to receive either continuous or cyclic daytime (8am to 8 pm) enteral feeding. Differences in circadian rhythms will be assessed by 24h patterns in core body temperature, heart rate variability, melatonin and peripheral clock gene expression. Secondary outcomes include depth of sleep, glucose variability and incidence of feeding intolerance. This study is expected to contribute to the optimalisation of circadian rhythms in the ICU.

Inclusion Criteria:

• Age ≥ 18 years old
• Receiving of or intention to start enteral nutrition via nasogastric or nasoduodenal tube
• Arterial line
• Expected duration of ICU admission > 48 hours

Exclusion Criteria:

• Receiving parenteral nutrition
• Prior night-time (20.00h - 8.00h) enteral tube feeding within the same hospitalization before study inclusion
• Readmission to ICU with prior study inclusion
• Chronic enteral tube feeding prior to current admission
• Presence of one or more contraindications of enteral feeding and/or at significant risk for gastrointestinal tolerance according to standard protocol (including but not limited to gastrointestinal haemorrhage, intestinal ischemia or necrosis, impaired digestive tract integrity due to obstruction or perforation, gastrectomy, enterectomy, history of gastroparesis or oesophageal dysmotility or expected surgery within 24 hours)
• Patients with glycaemic emergency (including but not limited to hyperglycaemic hyperosmolar nonketotic coma, diabetic ketoacidosis, severe hypoglycaemia resulting in ICU admission) or patients controlling their glucose levels and insulin dosing via continuous glucose monitoring
• Expected death within 24 hours
• Do-not-resuscitate (DNR) order
• Treatment with extracorporeal membrane oxygenation
• Severe neurological damage (significant neurological abnormalities such as bleeding, ischemia, neurotrauma or severe encephalopathy with Glasgow Coma Scale ≤ 8)
• Suspected or confirmed pregnancy

Immediately following publication, the individual participant data that underlie the results reported in the published article will be shared after deidentificiation. The data will be shared upon request with researchers who wish to access the data for any purpose.

The data will be available immediately following publication.

to be announced