Gastrointestinal dysfunction is common in critically ill patients and is closely associated with poor outcomes. However, its underlying mechanisms are complex, extending beyond local pathology, and bedside management remains inadequately defined. Conventional intensive care paradigms primarily interpret gastrointestinal manifestations as secondary, organ-specific complications and rely on static structural findings or pressure-based indicators, which often fail to detect early systemic deterioration. Increasing evidence indicates that gastrointestinal failure in critical illness reflects disrupted energy flow and a progressive entropy increase at the organism level. In this review, we propose a first-principles framework that conceptualizes critical illness as a disorder of energy redistribution, with the gastrointestinal system acting as a key node for both energy sacrifice and amplification of systemic instability. We highlight the role of bedside ultrasound as a real-time modality for visualizing gastrointestinal hemodynamics and perfusion. Ultrasound-derived parameters, including the superior mesenteric artery pulsatility index, portal venous flow patterns, and bowel wall characteristics, provide an integrated assessment of gastrointestinal perfusion and function and may serve as bedside surrogates of altered biological energy transfer. Finally, we outline ultrasound-guided, stage-based intervention pathways across major gastrointestinal critical scenarios, proposing an energy-oriented framework as a physiology-informed complement to existing protocol-driven care.
Jiang et al. (Tue,) studied this question.