Protocol for a feasibility randomised controlled trial of administering daytime only enteral feeding compared to standard continuous enteral feeding, to reduce delirium in mechanically ventilated, critically ill adults, with qualitative and circadian mechanistic sub-studies.

Abstract

Background: Survivors of critical illness describe delirium as a significant problem. Delirium is multi-factorial in origin and known to be associated with disrupted circadian rhythms. The timing of enteral feeding contributes to circadian rhythms. We hypothesised that the normal practice of providing continuous enteral nutrition during critical illness may contribute to delirium, due to the adverse effects on circadian rhythms.

Methods: DAYDREAM is a multicentre, open-label, randomised controlled feasibility trial conducted in two UK ICUs. Forty mechanically ventilated adult patients requiring enteral nutrition will be randomised 1:1 to receive either daytime-only feeding (08:00-22:00) or standard continuous enteral feeding. The primary outcomes are feasibility metrics, including recruitment, retention, intervention fidelity, and completeness of data collection. Secondary outcomes include delirium- and coma-free days (assessed using RASS and CAM-ICU), feeding intolerance, glycaemic control, ICU length of stay, and 90-day mortality. A nested qualitative sub-study will explore staff acceptability and implementation barriers. A mechanistic sub-study will evaluate circadian rhythmicity using physiological and biochemical markers between days 3 and 5 of ICU admission.

Results: Recruitment commenced in December 2025, with completion anticipated in 2027. Findings will inform the design and delivery of a subsequent definitive multicentre trial.

Conclusion: This study will determine the feasibility of implementing daytime-only enteral feeding in critically ill adults and provide preliminary data on its clinical and circadian effects.