Intermittent feeding and circadian rhythm in critical illness

Interorgan rhythmicity as a feature of healthful metabolism

The finding that animals with circadian gene mutations exhibit diet-induced obesity and metabolic syndrome with hypoinsulinemia revealed a distinct role for the clock in the brain and peripheral tissues. Obesogenic diets disrupt rhythmic sleep/wake patterns, feeding behavior, and transcriptional networks, showing that metabolic signals reciprocally control the clock. Providing access to high-fat diet only during the sleep phase (light period) in mice accelerates weight gain, whereas isocaloric time-restricted feeding during the active period enhances energy expenditure due to circadian induction of adipose thermogenesis. This perspective focuses on advances and unanswered questions in understanding the interorgan circadian control of healthful metabolism.

Enteral feeding strategies in patients with acute gastrointestinal injury: From limited to progressive to open feeding

Acute gastrointestinal injury (AGI) is very common in critically ill patients, and its severity is positively correlated with mortality. Critically ill patients with digestive and absorption dysfunction caused by AGI face higher nutritional risks, making nutritional support particularly important. Early enteral nutrition (EN) support is extremely important because it can promote the recovery of intestinal function, protect the intestinal mucosal barrier, reduce microbiota translocation, reduce postoperative complications, shorten hospital stay, and improve clinical prognosis. In recent years, many nutritional guidelines have been proposed for critically ill patients; however, there are few recommendations for the implementation of EN in patients with AGI, and their quality of evidence is low. The use of EN feeding strategies in critically ill patients with AGI remains controversial. The aim of this review was to elaborate on how EN feeding strategies should transition from limited to progressive to open feeding and explain the time window for this transition.

Pediatric Intensive Care Unit related Sleep and Circadian Dysregulation: a focused review

The pediatric intensive care unit (PICU) is bright, loud, and disruptive to children. Strategies to improve the sleep of adults in the ICU have improved delirium and mortality rates. Children need more sleep than adults for active growth, healing, and development when well; this is likely true when they are critically ill. This review was performed to describe what we know in this area to date with the intent to identify future directions for research in this field. Since the 1990s, 16 articles on 14 observational trials have been published investigating the sleep on a total of 312 critically ill children and the melatonin levels of an additional 144. Sleep measurements occurred in 9 studies through bedside observation (n = 2), actigraphy (n = 2), electroencephalogram (n = 1) and polysomnography (n = 4), of which polysomnography is the most reliable. Children in the PICU sleep more during the day, have fragmented sleep and disturbed sleep architecture. Melatonin levels may be elevated and peak later in critically ill children. Early data suggest there are at-risk subgroups for sleep and circadian disruption in the PICU including those with sepsis, burns, traumatic brain injury and after cardiothoracic surgery. The available literature describing the sleep of critically ill children is limited to small single-center observational studies with varying measurements of sleep and inconsistent findings. Future studies should use validated measurements and standardized definitions to begin to harmonize this area of medicine to build toward pragmatic interventional trials that may shift the paradigm of care in the pediatric intensive care unit.

Sleep during and following critical illness: A narrative review

Sleep is a complex process influenced by biological and environmental factors. Disturbances of sleep quantity and quality occur frequently in the critically ill and remain prevalent in survivors for at least 12 mo. Sleep disturbances are associated with adverse outcomes across multiple organ systems but are most strongly linked to delirium and cognitive impairment. This review will outline the predisposing and precipitating factors for sleep disturbance, categorised into patient, environmental and treatment-related factors. The objective and subjective methodologies used to quantify sleep during critical illness will be reviewed. While polysomnography remains the gold-standard, its use in the critical care setting still presents many barriers. Other methodologies are needed to better understand the pathophysiology, epidemiology and treatment of sleep disturbance in this population. Subjective outcome measures, including the Richards-Campbell Sleep Questionnaire, are still required for trials involving a greater number of patients and provide valuable insight into patients’ experiences of disturbed sleep. Finally, sleep optimisation strategies are reviewed, including intervention bundles, ambient noise and light reduction, quiet time, and the use of ear plugs and eye masks. While drugs to improve sleep are frequently prescribed to patients in the ICU, evidence supporting their effectiveness is lacking.

Current role and future perspectives of electroacupuncture in circadian rhythm regulation

In recent years, in-depth research on chronobiology has been conducted, and the circadian rhythm has become a new target for the treatment of diseases. Circadian rhythms are closely related to the normal physiological functions of organisms. Increasing evidence indicates that circadian rhythm disorders are the pathological basis of diseases such as sleep disorders, depression, cardiovascular diseases, and cancer. As an economical, safe, and effective treatment method, electroacupuncture has been widely used in clinical practice. In this paper, we summarize the current literature on electroacupuncture's regulation of circadian rhythm disorders and circadian clock genes. In addition, we briefly explore the optimization of electroacupuncture intervention programmes and the feasibility of implementing electroacupuncture intervention programmes at selected times in clinical practice. We conclude that electroacupuncture may have good application prospects in circadian rhythm regulation, but this conclusion needs to be confirmed by clinical trials.

Current insights in ICU nutrition: tailored nutrition

PURPOSE OF REVIEW

To summarize recent research on critical care nutrition focusing on the optimal composition, timing, and monitoring of enteral feeding strategies for (post)-ICU patients. We provide new insights on energy and protein recommendations, feeding intolerance, and describe nutritional practices for coronavirus disease 2019 ICU patients.

RECENT FINDINGS

The use of indirect calorimetry to establish individual energy requirements for ICU patients is considered the gold standard. The limited research on optimal feeding targets in the early phase of critical illness suggests avoiding overfeeding. Protein provision based upon the absolute lean body mass is rational. Therefore, body composition measurements should be considered. Body impedance analysis and muscle ultrasound seem reliable, affordable, and accessible methods to assess body composition at the bedside. There is inadequate evidence to change our practice of continuous enteral feeding into intermittent feeding. Finally, severe acute respiratory syndrome coronavirus 2 patients are prone to underfeeding due to hypermetabolism and should be closely monitored.

SUMMARY

Nutritional therapy should be adapted to the patient's characteristics, diagnosis, and state of metabolism during ICU stay and convalescence. A personalized nutrition plan may prevent harmful over- or underfeeding and attenuate muscle loss. Despite novel insights, more research is warranted into tailored nutrition strategies during critical illness and convalescence.