The Impact of Overnight Nutrition Support on Sleep and Circadian Rhythm Disruption in the ICU

The purpose of this study is to determine whether modifying the timing of nutrition support from overnight to daytime enhances sleep quality, preserves circadian rhythms, and improves overall inflammation and cardiometabolic profiles in postoperative patients in the cardiac surgical ICU on enteral nutrition.

Intensive care unit (ICU) environments do not support sleep or preserve circadian rhythms of postoperative critically ill patients. Among the contributing factors is the common practice of administering nutrition support through feeding tubes overnight. The overall objective of the study is to examine a novel dimension of clinical nutrition by determining whether enhancing sleep quality and preserving robust circadian rhythms through daytime instead of overnight feeds will attenuate inflammation and improve cardiometabolic profiles of postoperative cardiac ICU patients on nutrition support. The investigators hypothesize that overnight nutrition support results in fragmented sleep and blunted circadian rhythms and thus represent a modifiable mechanism exacerbating inflammation and cardiometabolic derangements in postoperative cardiac patients. Results of this study will help in the development of evidence-based, cost-efficient, and effective enteral nutrition timing countermeasures against fragmented sleep, disrupted circadian rhythms, inflammation and cardiometabolic derangements and potentially modify the current widespread practice of overnight nutrition likely affecting 250,000 hospital admissions annually in the United States.

Patients will start nighttime cycled enteral feeds first for 12 hours. Following a 24-hour washout period, patients will then start daytime cycled enteral feeds for 12 hours.

Patients will start daytime cycled enteral feeds first for 12 hours. Following a 24-hour washout period, patients will then start nighttime cycled enteral feeds for 12 hours.

Sleep fragmentation is defined as the number of shifts from deeper (N2, N3, REM) to lighter (W or N1) sleep stages by hours of sleep. Sleep fragmentation will be assessed objectively through EEG measures.

Approximately 12 hours. Estimated from nighttime sleep following daytime cycled enteral feeds and during nighttime cycled enteral feeds.

Amplitude is defined as peak-to-nadir difference in rhythms estimated from body temperature and actigraphy.

Estimated from data collected 12 hours prior to and the 12 hours during daytime cycled and nighttime cycled enteral feeds.

Sleep arousals is defined as n shifts from N1, N2, N3, REM to wake divided by hours of sleep. Sleep arousals will be assessed objectively through EEG measures.

Approximately 12 hours. Estimated from nighttime sleep following daytime cycled enteral feeds and during nighttime cycled enteral feeds.

Approximately 12 hours. Estimated from nighttime sleep following daytime cycled enteral feeds and during nighttime cycled enteral feeds.

Duration of the following sleep stages will be estimated: N1, N2, N3, REM sleep. Sleep stages will be assessed objectively through EEG measures.

Approximately 12 hours. Estimated from nighttime sleep following daytime cycled enteral feeds and during nighttime cycled enteral feeds.

Sleep midpoint is defined as the midpoint between start and end of sleep episode. Sleep midpoint will be determined objectively from EEG measures.

Approximately 12 hours. Estimated from nighttime sleep following daytime cycled enteral feeds and during nighttime cycled enteral feeds.

Estimated from data collected 12 hours prior to and the 12 hours during daytime cycled and nighttime cycled enteral feeds.

Estimated from data collected 12 hours prior to and the 12 hours during daytime cycled and nighttime cycled enteral feeds.

Estimated from data collected 12 hours prior to and the 12 hours during daytime cycled and nighttime cycled enteral feeds.

Estimated from data collected 12 hours prior to and the 12 hours during daytime cycled and nighttime cycled enteral feeds.

Continuously measured using ECG. Systolic and diastolic blood pressure will be averaged during each 12-hour cycled feed.

Estimated from data collected 12 hours prior to and the 12 hours during daytime cycled and nighttime cycled enteral feeds.

Continuously measured using continuous glucose sensors. Blood glucose will be averaged during each 12-hour cycled feed.

Estimated from data collected 12 hours prior to and the 12 hours during daytime cycled and nighttime cycled enteral feeds.

Inclusion Criteria: Adult male or non-pregnant female volunteers (age 18+) Scheduled for a cardiac surgical procedure with planned post-operative admission to the ICU for >48 hours Able and willing to give consent and comply with study procedures Exclusion Criteria: Blind, deaf or unable to speak English Women who are pregnant or nursing Contraindications to safe use enteral nutrition, including gastrointestinal obstruction Personal history of intestinal malabsorption, gallbladder disease or pancreatitis Dietary restrictions precluding enteral feeds Renal and liver failure requiring dialysis or Child-Pugh score > 7 Chronic therapy with benzodiazepines and/or antipsychotics Severe deficit due to structural or anoxic brain damage With skin condition that precludes wearing sensors